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Stress Induced Blindness - Effects Of Emotions On Glaucoma
From: Ray Bonar )
Subject: Angle-closure Glaucoma - Clinical types Date: 1997/12/27 Angle-closure Glaucoma - Clinical types Robert Ritch Ronald F. Lowe The nomenclature for the various clinically distinct types and modes of presentation of angle-closure glaucoma has been inconsistently used by different investigators, by investigators in different countries, and at different points in time. As a result, there is a moderate amount of confusion regarding terminology. This pertains in particular to the terms intermittent, prodromal, and subacute; chronic and creeping; and combined mechanism versus mixed mechanism. Angle-closure glaucoma has long been divided by convention into "primary" and "secondary" forms. Primary angle-closure, or relative pupillary block, is the most common mechanism of angle-closure glaucoma and studies of series of patients with acute angle-closure have been based on this concept. It should be recognized that publications dealing with characteristics of patients with "angle-closure glaucoma" include not only relative pupillary block but other mechanisms as well. However, because relative pupillary block forms the greatest proportion, the data should be regarded as not inordinately skewed. PRESENTATION Angle-closure glaucoma can present with a spectrum of symptomatology, from none at all to severe pain, blurred vision, and nausea. The terminology is based upon the signs and symptoms at the time of diagnosis, and these should not be though of as specific "types" of angle-closure, but merely descriptive phenomena which may vary with time in any individual patient (see Fig. 38-1). For example, a patient with a narrow angle and peripheral anterior synechiae (chronic angle-closure) may have symptoms of intermittent angle-closure attacks which, if not detected or diagnosed, can later present as acute angle-closure glaucoma. The mode of presentation depends on a combination of the percentage of the filtering meshwork occluded by the iris, the rapidity with which the occlusion occurs, and the ease of reversal of the iridotrabecular block. Fourman[Fourman, 1989 #2738] has published a useful flow chart to aid the ophthalmologist in dealing with acute angle-closure glaucoma. Intermittent angle-closure Intermittent angle-closure defines repeated, brief episodes of angle-closure with mild symptoms and elevated intraocular pressure. These resolve spontaneously and ocular function is normal between attacks. Intermittent angle-closure is often a prelude to acute angle-closure. The intraocular pressure is high enough to cause symptoms, but not as high as in a full-blown attack. This may be due to partial angle-closure, which could affect more the narrower superior part of the angle,[Leighton, 1971 #184] or 360° of closure with just enough functioning meshwork remaining above the level of closure to allow some aqueous to escape, or perhaps to a freely reactive pupil, which allows spontaneous reversal of the symptoms once the triggering element is removed. Intermittent attacks are most commonly associated with fatigue, dim light, and using the eyes for near work (see Table 38-1). They tend to recur under similar circumstances and at about the same time of day or evening. The symptoms are a dull ache in or around one eye and mildly blurred vision. Halos around lights are often not seen unless the patient is outdoors. Haloes are believed to result from stretching of the corneal lamellae, causing the cornea to act as a diffraction grating, producing a blue-green central halo and a yellow-red peripheral one. Halos that are seen every night are caused by cataracts, corneal disease, or persistently high intraocular pressure. Transient monocular visual loss has also been noted.[Ravitz, 1984 #185] The patient may recognize the cause and avoid or reduce the activity, such as watching television or reading. The attacks last for about a half hour after cessation of the inciting activity. Sleep is so often recognized as beneficial that many patients go to bed early or take a nap to obtain relief. Amelioration of the attack is attributed to sleep-induced miosis and possibly to decreased intraocular pressure resulting from decreased aqueous humor secretion.[Reiss, 1984 #186] If the symptoms persist overnight, a true attack has developed. Initially, intermittent attacks occur at intervals of weeks or months, but eventually may occur almost nightly. They may continue uneventfully for months or years. Usually only one eye is involved, but bilateral attacks can occur. Because the eyes appear normal between attacks except for a narrow angle, the diagnosis is frequently missed, and even ophthalmologists may be misled by the patient's self-diagnosis of migraine, sinusitis, anxiety or eyestrain. Examination reveals shallow anterior chambers, iris bombé, narrow angles, and sometimes an enlarged or oval pupil. Provocative testing may result in angle-closure, elevated intraocular pressure, and reproduction of the patient's symptoms. The end result of intermittent angle-closure glaucoma usually differs between whites and races with thick, heavily pigmented irides. In whites the attacks are essentially benign and may recur for years without causing damage. Attacks may be accompanied by progressive PAS formation, leading to chronic angle-closure. The greatest danger lies in the possibility of sudden conversion to acute angle-closure glaucoma. Laser iridotomy is definitive if the eye is otherwise normal and the angle not occludable by mechanisms other than pupillary block. In Asians the history may be consistent with intermittent angle-closure glaucoma, but the intraocular pressure is often elevated and the angle variably closed by PAS, depending on the frequency and severity of the attacks. Asian eyes are more prone to "creeping" angle-closure and PAS formation. Iridotomy alone may be insufficient to control intraocular pressure. Blacks also have a greater tendency to develop chronic angle-closure, but it is our impression that the anterior chambers are often deeper than those of Asians and that iris bombé is much less frequent. Both intermittent and acute attacks are less common in blacks than in Asians. Comparative biometric studies would greatly help to increase our understanding of angle-closure in these groups. Subacute angle-closure glaucoma Subacute angle-closure describes a stage in which attacks may be more frequent and prolonged than in intermittent angle-closure, but less so than in acute angle-closure. At least in some cases, this is caused by less than total closure of the angle.[Chandler, 1955 #187] Symptoms of blurred vision, pain, and halos may be more marked than in intermittent angle-closure. Attacks may occur over months or years, finally leading to an acute attack. Subacute attacks are much more common in Asians than in whites and can cause severe damage without much inflammation. They tend to produce a chronically dilated pupil, mild iris atrophy, PAS, and pigment on the iris close to the inferior angle. Intraocular pressure levels and glaucomatous disc and visual field damage vary according to the severity and duration of the attacks. Acute Angle-closure Glaucoma Precipitating events Acute angle-closure glaucoma can lead to irreversible damage. Various stimuli may trigger an attack. Most attacks occur during the evening, beginning mildly and rapidly increasing in severity. Approximately one-third of patients describe episodes of intermittent or subacute angle-closure having occurred before the acute attack. The physiological factors that convert relative pupillary block to absolute pupillary block remain poorly understood, as are those that determine whether an eye will develop acute or chronic angle-closure. Although pupillary block is the common underlying mechanism, the course of the disease depends on the degree and suddenness of the block, the flaccidity and physiologic responses of the iris, and the width and depth of the anterior chamber angle. Absolute pupillary block is most commonly triggered when the pupil is middilated, about 3.5 to 6 mm in diameter.[Chandler, 1952 #105] In this position, the combination of pupillary block and relaxation of the peripheral iris, allowing its forward displacement into the anterior chamber, are maximal. Mapstone[Mapstone, 1968 #127] concluded that the posteriorly directed forces of the dilator and sphincter muscles and the stretching force of the sphincter during contraction are greatest when the pupil is middilated. The most common precipitating events include illness, emotional stress, trauma, intense concentration, and pharmacologic pupillary dilation.[Sugar, 1941 #116; Lowe, 1961 #8957] The role of emotional stress in inducing acute angle-closure should not be underestimated.[Inman, 1929 #190; Egan, 1955 #189; Cross, 1960 #188] A memorable example was a patient who, after narrowly missing being injured by a grenade thrown through his living room window as an expression of some differences of opinion, immediately developed bilateral attacks. Attacks rarely begin simultaneously in both eyes. Minor differences in anterior chamber depth almost invariably result in the eye with the shallower chamber being involved first. A multitude of other inciting factors have been presented in case reports, including acute infectious disorders, acquired immunodeficiency syndrome, tumors, and trauma. In many of these cases, the mechanism either has not been delineated or the block is posterior to the lens, due to uveal effusion. Symptoms and signs The symptoms of an acute attack result from the sudden, marked elevation of intraocular pressure to as high as 80 mmHg. Corneal edema results in blurred vision and intense pain and, secondarily, in lacrimation and lid edema. These, in combination with anxiety and fatigue, lead to nausea and vomiting, whereas vasovagal responses cause bradycardia and diaphoresis. Systemic symptoms may be so severe as to mislead the nonophthalmologist, and some patients have actually undergone unwarranted exploratory laparotomy. We saw one patient whose ataxia, blurred vision, and diagnosis of multiple sclerosis disappeared after laser iridotomy. The diagnosis is usually straightforward (Fig. 38-2). Central visual acuity is reduced and the intraocular pressure is markedly elevated. The lids are swollen and there is conjunctival hyperemia and circumcorneal injection. The cornea is edematous and the pupil usually middilated and vertically oval because of iris sphincter ischemia. The anterior chamber is shallow but usually formed centrally, whereas the midperipheral iris is bowed anteriorly and may touch the cornea peripherally. An inflammatory reaction is present in the anterior chamber. Hypopyon can occur in severe or prolonged attacks.[Zhang, 1984 #8961; Friedman, 1972 #8966] Corneal edema may initially limit gonioscopic and posterior segment examination, even after the topical application of glycerin. Inability to open the angle with indentation gonioscopy at this stage does not mean that the angle will remain sealed after iridotomy, nor does it accurately reflect the presence or extent of PAS. Examination of the opposite eye is particularly useful in differentiating acute angle-closure glaucoma from neovascular, uveitic or phacolytic glaucoma, and usually reveals a shallow anterior chamber and narrow angle. The optic nerve head may be hyperemic and edematous early in the attack. With prolonged attacks or cases in which unrecognized chronic angle-closure glaucoma precedes an acute attack, pallor and cupping, along with visual field damage, may be present. Central retinal vein occlusion may occur as a result of an acute attack[Tornquist, 1958 #195; Sonty, 1981 #2801] or may precipitate one.[Bloome, 1977 #630; Grant, 1973 #631; Hyams, 1972 #632; Mendelsohn, 1985 #633; Weber, 1987 #634; Segal, 1986 #2796] Visual field changes associated with acute pressure elevation usually show nonspecific generalized or upper field constriction.[McNaught, 1974 #191] Early loss of central vision, enlargement of the blind spot, and nerve fiber bundle defects may be found.[Douglas, 1975 #204; Horie, 1975 #635] After normalization of intraocular pressure, the visual fields may also normalize, or patients may be left with reduced color vision, generalized decreased sensitivity, or specific defects. These may be exaggerated by cataract formation or progression. An attack may terminate spontaneously if iris atrophy from tissue necrosis allows aqueous humor to percolate through the iris stroma, equivalent functionally to a spontaneous iridotomy.(Fig. 38-4) However, this occurs more frequently as a result of suppression of aqueous secretion by the high pressure. Spontaneous termination may also be facilitated by a change in the position of the lens-iris contact, or segmental iris constriction with peaking of the pupil.[Phillips, 1963 #192] Chronic Angle-closure Glaucoma Chronic angle-closure refers to an eye in which portions of the anterior chamber angle are permanently closed by PAS. Variable and sometimes conflicting terminology has been used to describe somewhat differently appearing forms. The approach to therapy is similar in all of them. The terminology used in this section is an attempt to differentiate the two pathways by which chronic angle-closure can develop. In the first, iris bombé from relative pupillary block may appositionally close the angle. Prolonged apposition or repeated subacute attacks lead to gradual PAS formation. These usually begin in the superior angle, which is narrower than the inferior angle,[Bhargava, 1973 #142; Mapstone, 1977 #636] as pinpoint synechiae reaching to the midtrabecular meshwork and then gradually expanding in width. In early cases, in which appositional closure is present but PAS have not yet formed, we prefer the term chronic appositional closure. This condition can lead to elevated intraocular pressure and glaucomatous disc and visual field damage without PAS formation.[Foulds, 1957 #637] Eyes with progressive PAS formation may eventually develop an acute attack of angle-closure when pupillary block results in closure of the remaining portions of the angle unaffected by PAS. Many cases, however, develop elevated intraocular pressure and glaucomatous damage in the absence of symptoms. The presentation is similar to that of open-angle glaucoma, with progression of glaucomatous cupping and visual field loss. This is the situation most commonly associated in the United States with chronic angle-closure glaucoma. However, eyes with the same appearance but normal intraocular pressure merely constitute an earlier stage. PAS may also form during an acute attack, remaining after iridotomy has opened the unaffected portions of the angle. These PAS are usually high and broad. When first observed at this stage, it is impossible to determine whether the PAS formed before or during the attack, or at both times. In eyes with darker irides, a second mechanism of progressive angle-closure is more common. The closure is circumferential and begins in the deepest portion of the angle. Closure occurs more evenly in all quadrants, so that the angle progressively becomes more shallow. The appearance over time is of a progressively more anterior iris insertion. Lowe[Lowe, 1964 #194] has termed this creeping angle-closure. The PAS gradually creep up the ciliary face to the scleral spur and then to the trabecular meshwork. Insertion of the iris at or anterior to the scleral spur is rare in young individuals, and in many eyes with angle-closure glaucoma that have such an insertion, creeping angle-closure is the underlying reason. Creeping angle-closure is uncommon in whites but much more prevalent in Asians, in whom it ranks high as a cause of blindness. Black patients with angle-closure also tend to have this form. It occurs in eyes with slightly deeper, though still shallow, anterior chambers than are found in acute angle-closure. The gradual shortening of the angle in the presence of iris bombé brings the peripheral iris close to the external angle wall more and more anteriorly, narrowing the gap between the iris and the trabecular meshwork. Eventually, an acute attack may supervene (more commonly in Asians), or the PAS may permanently occlude the trabecular meshwork and lead to elevated intraocular pressure and glaucomatous damage (more commonly in black patients). The intraocular pressure in eyes with chronic angle-closure may be normal or elevated. As PAS formation progresses in the absence of intermittent attacks, the pressure rises gradually as less and less functional trabecular meshwork becomes available. In eyes with intermittent attacks, the pressure rises more rapidly relative to the extent of PAS formation caused by recurrent damage to the trabecular meshwork by the transient angle-closure. Dispersed pigment granules collect in the iridocorneal angle where the peripheral iris is in contact with the cornea. Dense blotches of pigment on the meshwork, particularly in the superior angle, or deposits of black pigment in the angle of a lightly pigmented iris, are highly suggestive of previous appositional closure. If the angle opens, this deposited line of pigment shows the extent of previous angle closure and can sometimes be a helpful diagnostic feature. The anterior chamber is quiet and usually deeper than in eyes with acute angle-closure glaucoma. The pupil is normal. The gradual elevation of intraocular pressure does not result in corneal endothelial decompensation, and edema is rare. The intraocular pressure is usually less than 40 mmHg and does not reach the levels found in acute angle-closure glaucoma. Symptoms are absent until the pressure rises high enough to affect the cornea or until extensive visual field damage has occurred. Although iridotomy will eliminate the pupillary block, intraocular pressure often remains elevated, and further medical treatment or surgery is required. Absolute Glaucoma Absolute glaucoma refers to an eye with no light perception and a persistently elevated intraocular pressure. The angle initially may be open or closed, but in phakic eyes an intumescent cataract often develops and leads to an associated angle-closure. The time required for a neglected angle-closure attack to cause total blindness is variable and depends on the severity of the acute attack, but appears to be an average of 1 to 2 years. Treatment is palliative and intraocular surgery is unwarranted. If corneal edema and pain are not relieved by topical beta-adrenergic blocking agents, steroids, and cycloplegics, noninvasive cycloablation may be performed. If this is insufficient or if complications such as phacolytic glaucoma develop, evisceration or enucleation may be necessary. Phthisis bulbi is not an uncommon outcome. PLATEAU IRIS Plateau iris configuration refers to the anatomic structure in which the iris root angulates forward and then centrally.[Tornquist, 1958 #195] In many cases, the iris root is short and is inserted anteriorly on the ciliary face, so that the angle is shallow and narrow, with a sharp drop-off of the peripheral iris at the inner aspect of the angle. The iris surface appears flat and the anterior chamber is not unusually shallow on slit-lamp examination. Plateau iris syndrome refers to the development of angle-closure, either spontaneously or after pupillary dilation, in an eye with plateau iris configuration despite the presence of a patent iridectomy or iridotomy. Some patients may develop acute angle-closure glaucoma[Godel, 1968 #196; Lowe, 1968 #197; Lowe, 1981 #198; Wand, 1977 #199] The risk of postoperative pupillary dilation after iridectomy or iridotomy is infrequently realized. Until recently, plateau iris syndrome was considered a rare entity. We have differentiated two subtypes.[Lowe, 1989 #2841] In the complete syndrome, which comprises the classic situation and is rare, intraocular pressure rises when the angle closes with pupillary dilation. In the incomplete syndrome, intraocular pressure does not change. The important factor differentiating the complete and incomplete syndromes is the level of the iris stroma with respect to the angle structures, or the "height" to which the plateau rises . If the angle closes to the upper trabecular meshwork or Schwalbe's line, intraocular pressure rises, whereas if the angle closes partially, leaving the upper portion of the filtering meshwork open, the pressure will not rise. This is a far more common situation and is clinically significant as these patients can develop PAS up to years after a successful iridotomy produces what appears as a well-opened angle. Plateau iris results from large and/or anteriorly positioned ciliary processes holding up the peripheral iris and maintaining its apposition to the trabecular meshwork ..[Pavlin, 1992 #240; Ritch, 1992 #1046; Wand, 1993 #3212] When indentation gonioscopy is performed in such an eye, the ciliary processes prevent posterior movement of the peripheral iris. As a result, a sinuous configuration results (sine wave sign), in which the iris follows the curvature of the lens, reaches its deepest point at the lens equator, then rises again over the ciliary processes before dropping peripherally. Much more force is needed during gonioscopy to open the angle than in pupillary block because the ciliary processes must be displaced, and the angle does not open as widely. In a morphometric study of the ciliary sulcus, Orgül et al.[Orgül, 1993 #2835] proposed that the displacement of the pars plicata from the peripheral iris to the iris root during embryogenesis may be incomplete in eyes of shorter axial length. Darkroom gonioscopy is important in plateau iris as well as in pupillary block, and an angle which appears open in the light can close in the dark. Patients with plateau iris tend to be female, younger (30s to 50s) and less hyperopic than those with relative pupillary block, and often have a family history of angle-closure glaucoma. Except in the rare younger patients (20s and 30s), some element of pupillary block is also present. However, because of the nature of the anatomic relationships of the structures surrounding the posterior chamber, the degree of relative pupillary block necessary to induce angle-closure is less than that in primary angle-closure glaucoma; this seems to account for the deeper anterior chamber and flatter iris surface in eyes with angle-closure and plateau iris. Patients with plateau iris who develop angle-closure glaucoma are also somewhat younger than those with pupillary block angle-closure glaucoma. As a general rule, the older the patient, the less prominent the angulation of the peripheral iris and the greater the element of pupillary block. Iridotomy is successful at opening the angle when a component of pupillary block is present, but periodic gonioscopy remains indicated, as the angle can narrow further with age due to enlargement of the lens. If plateau iris was not diagnosed before iridotomy and intraocular pressure is elevated postlaser, careful gonioscopy should be performed. If the angle is open, secondary damage to the trabecular meshwork or pigment liberation with dilation are the most likely causes. If the angle is closed, the differential diagnosis, besides plateau iris, should include malignant glaucoma, in which the anterior chamber is extremely shallow; PAS, which can be ruled out by indentation gonioscopy; or incomplete iridectomy. Although plateau iris syndrome is usually recognized in the postoperative period, it may develop years later. Patients with plateau iris configuration should not be assumed to be permanently cured, even though plateau iris syndrome does not develop immediately. IRIDOSCHISIS Iridoschisis is a separation of the anterior and posterior iris stromal layers which occurs primarily in older women. It is usually bilateral, but may be asymmetric. The amount of stromal separation can sometimes be dramatic. Iridoschisis has been associated in the literature with narrow angles and angle-closure glaucoma.[Romano, 1972 #203; Salmon, 1992 #8638; Loewenstein, 1948 #8969; Loewenstein, 1945 #8968; Haik, 1952 #8970; McCulloch, 1950 #8971; Mills, 1967 #8972; Rodrigues, 1983 #8973; Carter, 1953 #8974] Whether angle-closure requires an eye with a preexisting narrow angle is unknown. ANGLE-CLOSURE GLAUCOMAS ASSOCIATED WITH DRUGS AND OTHER DISORDERS Miotic-induced Angle-closure Glaucoma Prolonged miotic treatment in eyes with open-angle glaucoma and narrow angles may lead to pupillary block and angle-closure glaucoma. We have seen chronic angle-closure develop after several years of miotic therapy in eyes that initially had wide open angles. In some eyes, zonular relaxation occurs more readily than in others, so that anterior lens movement and an increase in axial lens thickness may facilitate pupillary block and angle-closure. In other eyes, there is little change in the lens, but progressively increasing pressure in the posterior chamber gradually pushes the peripheral iris against the trabecular meshwork. It is our impression that eyes with exfoliation syndrome are particularly prone to develop miotic-induced angle-closure. In these eyes, the iris is thicker and stiffer than normal due to deposition of exfoliation material within the stroma. In addition, zonular weakness allows the lens to move forward, leading to pupillary block. Less commonly, miotic therapy can have a pronounced effect on lens position and trigger malignant glaucoma.[Gorin, 1966 #625; Levene, 1972 #638; Merritt, 1977 #639; Rieser, 1972 #626] Unequal anterior chamber depths, a progressive increase in myopia, or progressive shallowing of the anterior chamber are clues to the correct diagnosis. Combined Mechanism Glaucoma Combined mechanism glaucoma refers to situations in which both open-angle and angle-closure components are present. A patient may have open-angle glaucoma and either narrow angles with superimposed intermittent angle-closure glaucoma or miotic-induced angle-closure. The most common situation is that in which angle-closure, either acute or chronic, is eliminated by iridotomy and/or iridoplasty and intraocular pressure still remains elevated, with or without the presence of PAS of any extent. Another situation occurs in eyes with exfoliation syndrome successfully treated for angle-closure glaucoma, in which open-angle glaucoma can develop independently years later with progressive blockage of the trabecular meshwork. In all of these cases, the residual open-angle component is treated as open-angle glaucoma. Mixed Mechanism Glaucoma This term is often used interchangeably with combined mechanism glaucoma, creating additional confusion. It is better to reserve this term to describe residual appositional angle-closure by another mechanism (plateau iris, phacomorphic, ciliary block) remaining after elimination of pupillary block with partial opening of the angle. Phacomorphic Glaucoma Swelling of the lens may convert an anterior chamber of medium depth into one that is markedly shallow and precipitate acute angle-closure glaucoma. In countries in which cataracts are prevalent and operations not readily available, acute angle-closure glaucoma from swollen hypermature lenses is common. Again, some element of pupillary block may also be present. Phacomorphic glaucoma is often unresponsive to medical therapy, and paradoxical reactions to pilocarpine are common. Pilocarpine, even in elderly patients, increases axial lens thickness and causes anterior lens movement, further shallowing the anterior chamber.[Abramson, 1973 #89] Slight lens subluxation in eyes of elderly patients, formerly termed senile subluxation of the lens, is most commonly associated with exfoliation syndrome. Mild iridodonesis may be seen. In some cases, anterior lens movement may be sufficient to cause angle-closure glaucoma, usually chronic. These eyes are more susceptible to the development of miotic-induced angle-closure during treatment for open-angle glaucoma. Iridotomy usually suffices to eliminate pupillary block and the angle-closure component. In younger patients anterior lens movement is often associated with secondary causes or ciliary block. After iridotomy, iridoplasty may be necessary to eliminate continued appositional closure if cycloplegics are unsuccessful at maintaining a more posterior lens position and an open angle. This topic is discussed more fully in Chapter 58. Malignant Glaucoma Malignant (ciliary block) glaucoma[Levene, 1972 #638; Shaffer, 1978 #640; Simmons, 1972 #641; Weiss, 1972 #642; Dueker, 1994 #4726] is a multifactorial disease in which the following components may play varying roles: (1) previous acute or chronic angle-closure glaucoma, (2) shallowness of the anterior chamber, (3) forward movement of the lens, (4) pupillary block by the lens or vitreous, (5) slackness of the zonules, (6) anterior rotation and/or swelling of the ciliary body, (7) thickening of the anterior hyaloid membrane, (8) expansion of the vitreous, and (9) posterior aqueous displacement into or behind the vitreous. This topic is covered in Chapter 39. Swelling or anterior rotation of the ciliary body with forward rotation of the lens-iris diaphragm and relaxation of the zonular apparatus causes anterior lens displacement which in turn causes direct angle-closure by physically pushing the iris agains the trabecular meshwork.[Phelps, 1974 #643] Accurate diagnosis and treatment are often more difficult when the initiating event is posterior to the lens-iris diaphragm. In predisposed eyes, miotic therapy can have a pronounced effect on lens position and trigger malignant glaucoma.[Gorin, 1966 #625; Levene, 1972 #638; Merritt, 1977 #639; Rieser, 1972 #626] Unequal anterior chamber depths, a progressive increase in myopia, or progressive shallowing of the anterior chamber are clues to the correct diagnosis. Malignant glaucoma may occur following cataract surgery with posterior chamber intraocular lens implantation.[Brown, 1986 #1255; Epstein, 1984 #1395; Lynch, 1986 #2773; Duy, 1987 #2729; Reed, 1990 #1054; Vajpayee, 1991 #2812; Tello, 1993 #1963] The differential diagnosis includes pupillary block, choroidal hemorrhage, and ciliochoroidal effusion with anterior rotation of the ciliary body and secondary angle closure. Shallowing of the central anterior chamber occurs in pseudophakic malignant glaucoma, but not in pupillary block. Rupture of the anterior hyaloid face is usually curative and allows aqueous to move into the anterior segment. We have examined several patients with presumed aqueous misdirection in whom an annular ciliary body detachment had caused anterior movement of the ciliary body. Whether a posterior diversion of aqueous flow is present in these disorders is unknown. Some of the disorders that can lead to this picture are covered in other chapters. These include drug sensitivity (e.g., sulfonamides, see Chapter 56); angle-closure after panretinal photocoagulation, central retinal vein occlusion, or scleral buckling procedures (see Chapters 50 and 51); uveal effusion from posterior segment inflammation; ciliary body swelling, inflammation, or cysts ; posterior segment tumors (see Chapter 52). Aphakic and pseudophakic malignant glaucoma are discussed in Chapter 61. Retinopathy of prematurity Angle-closure may occur in very young children with retinopathy of prematurity due to forward shifting of the lens-iris diaphragm (see also Chapter 44).[Cohen, 1964 #8926; Hittner, 1979 #1894; Pollard, 1980 #5292; McCormick, 1971 #1898; Laws, 1994 #8928; Kushner, 1982 #1057] These children do not respond to iridotomy. In young adults with this condition, there appears to be a superimposed element of pupillary block, and iridotomy may be successful.[Ueda, 1988 #8927; Smith, 1984 #1899] Nanophthalmos Nanophthalmos is a bilateral, often familial form of microphthalmos unaccompanied by other congenital malformations. It is characterized by hyperopia, small corneal diameter, thick sclera, and narrow angles.[O'Grady, 1971 #8231] Angle-closure glaucoma usually appears between the ages of 20 and 50 years. Although by definition, nanophthalmos refers to an eye of axial length less than 20 mm, there is obviously a gradient of hyperopic refraction, the degree of hyperopia correlating inversely with axial length. There is an inverse correlation between the degree of hyperopia and the age of onset of angle-closure. The youngest reported patient was 9 years old with 21 diopters of hyperopia.[Hatcher, 1952 #8962] However, acute angle-closure glaucoma can also develop in the elderly.[Cross, 1976 #8964] The sclera in nanophthalmic eyes is abnormally thick.[Brockhurst, 1975 #2710] Electron microscopy reveals disordered collagen bundles and fraying of collagen fibrils, with absence of elastic fibers.[Trelstad, 1982 #5595; Stewart, 1991 #2804] In tissue culture, scleral fibroblasts of eyes with nanophthalmos appear to have an abnormal glycosamine metabolism, which might explain the abnormal packing of collagen bundles and scleral thickening.[Shiono, 1992 #2798] Uveal effusion is common, either spontaneously or after surgical procedures, including filtration surgery or cataract extraction.[Brockhurst, 1975 #2710; Ryan, 1982 #8963] Associations with retinitis pigmentosa[Ghose, 1985 #8230; MacKay, 1987 #1042] and Hallerman-Streiff syndrome[Stewart, 1991 #2804] have been reported. Laser iridotomy for angle-closure is usually unsuccessful or only temporarily successful. If successful initially, lens enlargement with age can lead to appositional closure. Iridoplasty (gonioplasty) to flatten the peripheral iris was first reported in 1979 by Kimbrough et al.[Kimbrough, 1979 #1412] Combined iridotomy and iridoplasty often brings the angle-closure under control.[Jin, 1990 #2759] Uveal effusions have been reported after both laser iridotomy[Karjalainen, 1986 #1408] and trabeculoplasty.[Good, 1988 #2742] The risks of surgical intervention include malignant glaucoma, expulsive suprachoroidal hemorrhage, and retinal detachment.[Hyams, 1990 #8965] Posterior sclerotomy may or may not be successful at preventing uveal effusion.[Calhoun, 1975 #8047; Jin, 1990 #2759] Vortex vein decompression for nanophthalmic uveal effusion was described by Brockhurst,[Brockhurst, 1980 #5305] but the technique is technically difficult. Partial thickness sclerectomies and sclerostomies were reported in one patient to achieve complete resolution of retinal and choroidal detachments, suggesting impairment of transscleral protein transport as a primary pathophysiologic mechanism in nanophthalmic uveal effusion.[Allen, 1988 #1921] Subsequently, Wax et al. described success with anterior lamellar sclerectomy without sclerostomy.[Wax, 1992 #2820] CLINICAL PATHOLOGY OF ANGLE-CLOSURE GLAUCOMA When the angle totally occludes, aqueous outflow is blocked, and intraocular pressure rises markedly. The effect of the elevated pressure depends on the magnitude and rapidity of its rise. At the same time the pupillary reaction to direct light decreases. The pupil becomes partly dilated and tends to assume a vertically oval shape, but may be oblique or even horizontal. Cornea With very high intraocular pressure, corneal edema is severe. Transient loss of sensitivity can occur.[Patel, 1988 #2787] The cornea is cloudy and may be twice its usual thickness. Endothelial cell density is reduced by as much as 33% following an acute attack and is greater the longer the duration of the attack.[Bigar, 1982 #644; Mapstone, 1985 #121; Markowitz, 1984 #652; Brooks, 1991 #8958; Olsen, 1980 #3558; Malaise-Stals, 1984 #8959] Corneal decompensation may occur in eyes with preexisting endothelial compromise.[Krontz, 1988 #1932; Hyams, 1983 #8960] When the pressure is lowered, the edema clears first at the periphery. Folds in Descemet's membrane form. Following prolonged high pressure, corneal edema and striate keratopathy may persist for some days. With severe damage, chronic edema may persist, lipid is deposited, and the cornea may become fibrosed and vascularized. Iris Partial necrosis of the iris stroma is the first sign of damage from elevated intraocular pressure experimentally.[Anderson, 1975 #200] At pressures over 60 mmHg, the pupil becomes increasingly resistant to miotics, probably caused by direct pressure on the sphincter muscle.[Charles, 1970 #201] The sphincter may respond to miotics after the pressure has been lowered, but when intraocular pressure exceeds the diastolic blood pressure, the iris around the pupil becomes ischemic.[Charles, 1970 #201] The sphincter muscle then loses its ability to contract even if intraocular pressure is lowered, and patchy atrophy of the iris occurs. The dilator muscle is less affected than the sphincter, so that the instillation of 10% phenylephrine usually causes increased pupillary dilation. In the segments in which the stroma is not obviously atrophic, the pupillary margin is thick, rolled, and bunched with radial folds. At the margins of the atrophic area, the stromal fibers run obliquely to the periphery behind the edges of the atrophic area, thus producing a twisting of this border zone of the stroma[Winstanley, 1961 #202]. In severe and prolonged attacks, diffuse iris atrophy occurs. Sometimes a sector of the iris stroma will be disrupted and look like iridoschisis[Romano, 1972 #203]. This may occur with slow progressive atrophy months or years after the acute attack. The pigment epithelium and dilator muscle can be patchily affected and areas may transilluminate. Posterior synechiae may be minimal or extensive. After iridectomy aqueous humor flowing into the anterior chamber can bypass the pupil, favoring formation of postoperative posterior synechiae. Ciliary Body In 1973, Kerman et al.[Kerman, 1973 #645] reported that the ciliary processes may be inserted more anteriorly than normal and extend to the peripheral posterior iris in eyes with angle-closure. With the discovery that plateau iris is caused by large and/or anterior ciliary processes, it is now becoming evident that there is a spectrum of ciliary body size and position. The ciliary body itself does not appear to be adversely affected by acute angle-closure glaucoma. Lens Lens damage can occur as: (1) glaukomflecken, (2) anterior capsular cataract, (3) pigment deposition, posterior synechiae, and fibrosis, (4) cortical cataracts, and (5) nuclear sclerosis. Glaukomflecken ("glaucoma flakes"), or disseminated anterior subcapsular cataracts of acute glaucoma, are the most characteristic signs of lens damage from sudden severe rises of intraocular pressure. They are thought to be caused by pressure necrosis of anterior lens fibers and do not occur at the posterior pole. When intraocular pressure is very high, the lens damage simulates a thin, gray deposit of exudate on the lens surface.[Jones, 1959 #646] With a fall in pressure, the sheet becomes thinner in some places and more condensed in others. Holes develop within it, so it may appear as a coarse, irregular, white net.[Lowe, 1965 #647] Later these flakes become more discrete and appear as small, irregular, blue-white plaques. They tend to follow suture lines of the lens, suggesting necrosis of the tips of the lens fibers. Gradually, the flakes diminish and usually become relatively sparse. As new lens fibers grow from the equator, they overlie the flecks, which sink deeper into the lens and persist as permanent evidence. Glaukomflecken occur almost entirely within the pupil according to its size at the time of the attack.[Sugar, 1946 #648] Glaukomflecken are rare apart from acute angle-closure glaucoma, but have been seen after contusion and chemical burns and also when the anterior chamber has remained flat postoperatively with the cornea and lens in contact for some days. Occasionally, small white plaques resembling glaukomflecken may persist in the anterior surface of the lens. These are anterior capsular cataracts. Anterior cortical lens opacities commonly follow severe attacks of angle-closure glaucoma and may persist as faint irregular streaks that almost invariably progress. The first sign of nuclear sclerosis is a myopic refractive change, which may stabilize or progress. Following severe glaucomatous iritis with extensive posterior synechiae, fibrosis may extend from the iris onto the anterior lens surface. Zonules The zonules can be damaged, so with surgery the lens may move forward with the development of malignant (ciliary block) glaucoma. Occasionally, the opaque lens may slowly dislocate over the years and sink below the pupil. Choroid Kubota et al.[Kubota, 1993 #2833] reported decreased choroidal thickness in 12 eyes with angle-closure glaucoma associated with malignant melanoma of the ciliary body. The decreased thickness was primarily due to decreased choroidal vessel diameter, suggesting decreased choroidal perfusion. Retina and Optic Nerve In intermittent angle-closure glaucoma, even after many attacks, the optic disc is typically unaffected. During the initial states of an acute attack, the disc may appear normal, congested, or edematous with retinal venous congestion and retinal hemorrhages near the disc. When intraocular pressure is acutely elevated in owl monkeys, damage to the nerve fiber layer and ganglion cells precedes damage to most other tissues except the iris.[Anderson, 1975 #200] Douglas et al.[Douglas, 1975 #204] found pallor without cupping following acute attacks, and pallor and cupping in patients with chronic angle-closure. Acutely elevated intraocular pressure in monkeys leads to optic disc congestion lasting several days before pallor and cupping develop.[Zimmerman, 1967 #650] Large retinal hemorrhages near the disc can occur with sudden lowering of intraocular pressure as after hyperosmotic or carbonic anhydrase inhibitor therapy. Retinal function is depressed with raised intraocular pressure.[Uenoyama, 1969 #649] Abnormalities of visual evoked potentials have been reported.[Mitchell, 1989 #1906] In a histological study of 21 eyes with secondary angle-closure glaucoma, Jonas et al.[Jonas, 1992 #1051] found the lamina cribrosa significantly thinner, the optic cup deeper and wider, and the corpora amylacea count lower than in controls. Parapapillary atrophy was significantly greater and occurred more frequently in glaucomatous eyes and the parapapillary retina was significantly thinner.[Jonas, 1992 #1052] A significantly decreased photoreceptor, but not retinal pigment epithelial, cell count was reported in eyes with angle-closure following penetrating trauma.[Panda, 1992 #2786] The final effects will depend on severity and duration of the attack. Recovery may be complete or there may be contraction of isopters and nerve fiber bundle defects.[Douglas, 1975 #204; Lowe, 1973 #624] Pallor without cupping was found to be characteristic of discs after acute angle-closure glaucoma, whereas both pallor and cupping occurred in chronic angle-closure.[Douglas, 1975 #204] In prolonged attacks, when treatment is delayed, glaucomatous damage may progress to the point at which vision is reduced to perception of hand movements or light. In chronic angle-closure glaucoma, the visual field defects and optic disc cupping progress similarly to those of open-angle glaucoma. |
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From: Ray Bonar )
Subject: Angle-closure Glaucoma - Clinical types Date: 1997/12/27 Angle-closure Glaucoma - Clinical types Robert Ritch Ronald F. Lowe The nomenclature for the various clinically distinct types and modes of presentation of angle-closure glaucoma has been inconsistently used by different investigators, by investigators in different countries, and at different points in time. As a result, there is a moderate amount of confusion regarding terminology. This pertains in particular to the terms intermittent, prodromal, and subacute; chronic and creeping; and combined mechanism versus mixed mechanism. Angle-closure glaucoma has long been divided by convention into "primary" and "secondary" forms. Primary angle-closure, or relative pupillary block, is the most common mechanism of angle-closure glaucoma and studies of series of patients with acute angle-closure have been based on this concept. It should be recognized that publications dealing with characteristics of patients with "angle-closure glaucoma" include not only relative pupillary block but other mechanisms as well. However, because relative pupillary block forms the greatest proportion, the data should be regarded as not inordinately skewed. PRESENTATION Angle-closure glaucoma can present with a spectrum of symptomatology, from none at all to severe pain, blurred vision, and nausea. The terminology is based upon the signs and symptoms at the time of diagnosis, and these should not be though of as specific "types" of angle-closure, but merely descriptive phenomena which may vary with time in any individual patient (see Fig. 38-1). For example, a patient with a narrow angle and peripheral anterior synechiae (chronic angle-closure) may have symptoms of intermittent angle-closure attacks which, if not detected or diagnosed, can later present as acute angle-closure glaucoma. The mode of presentation depends on a combination of the percentage of the filtering meshwork occluded by the iris, the rapidity with which the occlusion occurs, and the ease of reversal of the iridotrabecular block. Fourman[Fourman, 1989 #2738] has published a useful flow chart to aid the ophthalmologist in dealing with acute angle-closure glaucoma. Intermittent angle-closure Intermittent angle-closure defines repeated, brief episodes of angle-closure with mild symptoms and elevated intraocular pressure. These resolve spontaneously and ocular function is normal between attacks. Intermittent angle-closure is often a prelude to acute angle-closure. The intraocular pressure is high enough to cause symptoms, but not as high as in a full-blown attack. This may be due to partial angle-closure, which could affect more the narrower superior part of the angle,[Leighton, 1971 #184] or 360° of closure with just enough functioning meshwork remaining above the level of closure to allow some aqueous to escape, or perhaps to a freely reactive pupil, which allows spontaneous reversal of the symptoms once the triggering element is removed. Intermittent attacks are most commonly associated with fatigue, dim light, and using the eyes for near work (see Table 38-1). They tend to recur under similar circumstances and at about the same time of day or evening. The symptoms are a dull ache in or around one eye and mildly blurred vision. Halos around lights are often not seen unless the patient is outdoors. Haloes are believed to result from stretching of the corneal lamellae, causing the cornea to act as a diffraction grating, producing a blue-green central halo and a yellow-red peripheral one. Halos that are seen every night are caused by cataracts, corneal disease, or persistently high intraocular pressure. Transient monocular visual loss has also been noted.[Ravitz, 1984 #185] The patient may recognize the cause and avoid or reduce the activity, such as watching television or reading. The attacks last for about a half hour after cessation of the inciting activity. Sleep is so often recognized as beneficial that many patients go to bed early or take a nap to obtain relief. Amelioration of the attack is attributed to sleep-induced miosis and possibly to decreased intraocular pressure resulting from decreased aqueous humor secretion.[Reiss, 1984 #186] If the symptoms persist overnight, a true attack has developed. Initially, intermittent attacks occur at intervals of weeks or months, but eventually may occur almost nightly. They may continue uneventfully for months or years. Usually only one eye is involved, but bilateral attacks can occur. Because the eyes appear normal between attacks except for a narrow angle, the diagnosis is frequently missed, and even ophthalmologists may be misled by the patient's self-diagnosis of migraine, sinusitis, anxiety or eyestrain. Examination reveals shallow anterior chambers, iris bombé, narrow angles, and sometimes an enlarged or oval pupil. Provocative testing may result in angle-closure, elevated intraocular pressure, and reproduction of the patient's symptoms. The end result of intermittent angle-closure glaucoma usually differs between whites and races with thick, heavily pigmented irides. In whites the attacks are essentially benign and may recur for years without causing damage. Attacks may be accompanied by progressive PAS formation, leading to chronic angle-closure. The greatest danger lies in the possibility of sudden conversion to acute angle-closure glaucoma. Laser iridotomy is definitive if the eye is otherwise normal and the angle not occludable by mechanisms other than pupillary block. In Asians the history may be consistent with intermittent angle-closure glaucoma, but the intraocular pressure is often elevated and the angle variably closed by PAS, depending on the frequency and severity of the attacks. Asian eyes are more prone to "creeping" angle-closure and PAS formation. Iridotomy alone may be insufficient to control intraocular pressure. Blacks also have a greater tendency to develop chronic angle-closure, but it is our impression that the anterior chambers are often deeper than those of Asians and that iris bombé is much less frequent. Both intermittent and acute attacks are less common in blacks than in Asians. Comparative biometric studies would greatly help to increase our understanding of angle-closure in these groups. Subacute angle-closure glaucoma Subacute angle-closure describes a stage in which attacks may be more frequent and prolonged than in intermittent angle-closure, but less so than in acute angle-closure. At least in some cases, this is caused by less than total closure of the angle.[Chandler, 1955 #187] Symptoms of blurred vision, pain, and halos may be more marked than in intermittent angle-closure. Attacks may occur over months or years, finally leading to an acute attack. Subacute attacks are much more common in Asians than in whites and can cause severe damage without much inflammation. They tend to produce a chronically dilated pupil, mild iris atrophy, PAS, and pigment on the iris close to the inferior angle. Intraocular pressure levels and glaucomatous disc and visual field damage vary according to the severity and duration of the attacks. Acute Angle-closure Glaucoma Precipitating events Acute angle-closure glaucoma can lead to irreversible damage. Various stimuli may trigger an attack. Most attacks occur during the evening, beginning mildly and rapidly increasing in severity. Approximately one-third of patients describe episodes of intermittent or subacute angle-closure having occurred before the acute attack. The physiological factors that convert relative pupillary block to absolute pupillary block remain poorly understood, as are those that determine whether an eye will develop acute or chronic angle-closure. Although pupillary block is the common underlying mechanism, the course of the disease depends on the degree and suddenness of the block, the flaccidity and physiologic responses of the iris, and the width and depth of the anterior chamber angle. Absolute pupillary block is most commonly triggered when the pupil is middilated, about 3.5 to 6 mm in diameter.[Chandler, 1952 #105] In this position, the combination of pupillary block and relaxation of the peripheral iris, allowing its forward displacement into the anterior chamber, are maximal. Mapstone[Mapstone, 1968 #127] concluded that the posteriorly directed forces of the dilator and sphincter muscles and the stretching force of the sphincter during contraction are greatest when the pupil is middilated. The most common precipitating events include illness, emotional stress, trauma, intense concentration, and pharmacologic pupillary dilation.[Sugar, 1941 #116; Lowe, 1961 #8957] The role of emotional stress in inducing acute angle-closure should not be underestimated.[Inman, 1929 #190; Egan, 1955 #189; Cross, 1960 #188] A memorable example was a patient who, after narrowly missing being injured by a grenade thrown through his living room window as an expression of some differences of opinion, immediately developed bilateral attacks. Attacks rarely begin simultaneously in both eyes. Minor differences in anterior chamber depth almost invariably result in the eye with the shallower chamber being involved first. A multitude of other inciting factors have been presented in case reports, including acute infectious disorders, acquired immunodeficiency syndrome, tumors, and trauma. In many of these cases, the mechanism either has not been delineated or the block is posterior to the lens, due to uveal effusion. Symptoms and signs The symptoms of an acute attack result from the sudden, marked elevation of intraocular pressure to as high as 80 mmHg. Corneal edema results in blurred vision and intense pain and, secondarily, in lacrimation and lid edema. These, in combination with anxiety and fatigue, lead to nausea and vomiting, whereas vasovagal responses cause bradycardia and diaphoresis. Systemic symptoms may be so severe as to mislead the nonophthalmologist, and some patients have actually undergone unwarranted exploratory laparotomy. We saw one patient whose ataxia, blurred vision, and diagnosis of multiple sclerosis disappeared after laser iridotomy. The diagnosis is usually straightforward (Fig. 38-2). Central visual acuity is reduced and the intraocular pressure is markedly elevated. The lids are swollen and there is conjunctival hyperemia and circumcorneal injection. The cornea is edematous and the pupil usually middilated and vertically oval because of iris sphincter ischemia. The anterior chamber is shallow but usually formed centrally, whereas the midperipheral iris is bowed anteriorly and may touch the cornea peripherally. An inflammatory reaction is present in the anterior chamber. Hypopyon can occur in severe or prolonged attacks.[Zhang, 1984 #8961; Friedman, 1972 #8966] Corneal edema may initially limit gonioscopic and posterior segment examination, even after the topical application of glycerin. Inability to open the angle with indentation gonioscopy at this stage does not mean that the angle will remain sealed after iridotomy, nor does it accurately reflect the presence or extent of PAS. Examination of the opposite eye is particularly useful in differentiating acute angle-closure glaucoma from neovascular, uveitic or phacolytic glaucoma, and usually reveals a shallow anterior chamber and narrow angle. The optic nerve head may be hyperemic and edematous early in the attack. With prolonged attacks or cases in which unrecognized chronic angle-closure glaucoma precedes an acute attack, pallor and cupping, along with visual field damage, may be present. Central retinal vein occlusion may occur as a result of an acute attack[Tornquist, 1958 #195; Sonty, 1981 #2801] or may precipitate one.[Bloome, 1977 #630; Grant, 1973 #631; Hyams, 1972 #632; Mendelsohn, 1985 #633; Weber, 1987 #634; Segal, 1986 #2796] Visual field changes associated with acute pressure elevation usually show nonspecific generalized or upper field constriction.[McNaught, 1974 #191] Early loss of central vision, enlargement of the blind spot, and nerve fiber bundle defects may be found.[Douglas, 1975 #204; Horie, 1975 #635] After normalization of intraocular pressure, the visual fields may also normalize, or patients may be left with reduced color vision, generalized decreased sensitivity, or specific defects. These may be exaggerated by cataract formation or progression. An attack may terminate spontaneously if iris atrophy from tissue necrosis allows aqueous humor to percolate through the iris stroma, equivalent functionally to a spontaneous iridotomy.(Fig. 38-4) However, this occurs more frequently as a result of suppression of aqueous secretion by the high pressure. Spontaneous termination may also be facilitated by a change in the position of the lens-iris contact, or segmental iris constriction with peaking of the pupil.[Phillips, 1963 #192] Chronic Angle-closure Glaucoma Chronic angle-closure refers to an eye in which portions of the anterior chamber angle are permanently closed by PAS. Variable and sometimes conflicting terminology has been used to describe somewhat differently appearing forms. The approach to therapy is similar in all of them. The terminology used in this section is an attempt to differentiate the two pathways by which chronic angle-closure can develop. In the first, iris bombé from relative pupillary block may appositionally close the angle. Prolonged apposition or repeated subacute attacks lead to gradual PAS formation. These usually begin in the superior angle, which is narrower than the inferior angle,[Bhargava, 1973 #142; Mapstone, 1977 #636] as pinpoint synechiae reaching to the midtrabecular meshwork and then gradually expanding in width. In early cases, in which appositional closure is present but PAS have not yet formed, we prefer the term chronic appositional closure. This condition can lead to elevated intraocular pressure and glaucomatous disc and visual field damage without PAS formation.[Foulds, 1957 #637] Eyes with progressive PAS formation may eventually develop an acute attack of angle-closure when pupillary block results in closure of the remaining portions of the angle unaffected by PAS. Many cases, however, develop elevated intraocular pressure and glaucomatous damage in the absence of symptoms. The presentation is similar to that of open-angle glaucoma, with progression of glaucomatous cupping and visual field loss. This is the situation most commonly associated in the United States with chronic angle-closure glaucoma. However, eyes with the same appearance but normal intraocular pressure merely constitute an earlier stage. PAS may also form during an acute attack, remaining after iridotomy has opened the unaffected portions of the angle. These PAS are usually high and broad. When first observed at this stage, it is impossible to determine whether the PAS formed before or during the attack, or at both times. In eyes with darker irides, a second mechanism of progressive angle-closure is more common. The closure is circumferential and begins in the deepest portion of the angle. Closure occurs more evenly in all quadrants, so that the angle progressively becomes more shallow. The appearance over time is of a progressively more anterior iris insertion. Lowe[Lowe, 1964 #194] has termed this creeping angle-closure. The PAS gradually creep up the ciliary face to the scleral spur and then to the trabecular meshwork. Insertion of the iris at or anterior to the scleral spur is rare in young individuals, and in many eyes with angle-closure glaucoma that have such an insertion, creeping angle-closure is the underlying reason. Creeping angle-closure is uncommon in whites but much more prevalent in Asians, in whom it ranks high as a cause of blindness. Black patients with angle-closure also tend to have this form. It occurs in eyes with slightly deeper, though still shallow, anterior chambers than are found in acute angle-closure. The gradual shortening of the angle in the presence of iris bombé brings the peripheral iris close to the external angle wall more and more anteriorly, narrowing the gap between the iris and the trabecular meshwork. Eventually, an acute attack may supervene (more commonly in Asians), or the PAS may permanently occlude the trabecular meshwork and lead to elevated intraocular pressure and glaucomatous damage (more commonly in black patients). The intraocular pressure in eyes with chronic angle-closure may be normal or elevated. As PAS formation progresses in the absence of intermittent attacks, the pressure rises gradually as less and less functional trabecular meshwork becomes available. In eyes with intermittent attacks, the pressure rises more rapidly relative to the extent of PAS formation caused by recurrent damage to the trabecular meshwork by the transient angle-closure. Dispersed pigment granules collect in the iridocorneal angle where the peripheral iris is in contact with the cornea. Dense blotches of pigment on the meshwork, particularly in the superior angle, or deposits of black pigment in the angle of a lightly pigmented iris, are highly suggestive of previous appositional closure. If the angle opens, this deposited line of pigment shows the extent of previous angle closure and can sometimes be a helpful diagnostic feature. The anterior chamber is quiet and usually deeper than in eyes with acute angle-closure glaucoma. The pupil is normal. The gradual elevation of intraocular pressure does not result in corneal endothelial decompensation, and edema is rare. The intraocular pressure is usually less than 40 mmHg and does not reach the levels found in acute angle-closure glaucoma. Symptoms are absent until the pressure rises high enough to affect the cornea or until extensive visual field damage has occurred. Although iridotomy will eliminate the pupillary block, intraocular pressure often remains elevated, and further medical treatment or surgery is required. Absolute Glaucoma Absolute glaucoma refers to an eye with no light perception and a persistently elevated intraocular pressure. The angle initially may be open or closed, but in phakic eyes an intumescent cataract often develops and leads to an associated angle-closure. The time required for a neglected angle-closure attack to cause total blindness is variable and depends on the severity of the acute attack, but appears to be an average of 1 to 2 years. Treatment is palliative and intraocular surgery is unwarranted. If corneal edema and pain are not relieved by topical beta-adrenergic blocking agents, steroids, and cycloplegics, noninvasive cycloablation may be performed. If this is insufficient or if complications such as phacolytic glaucoma develop, evisceration or enucleation may be necessary. Phthisis bulbi is not an uncommon outcome. PLATEAU IRIS Plateau iris configuration refers to the anatomic structure in which the iris root angulates forward and then centrally.[Tornquist, 1958 #195] In many cases, the iris root is short and is inserted anteriorly on the ciliary face, so that the angle is shallow and narrow, with a sharp drop-off of the peripheral iris at the inner aspect of the angle. The iris surface appears flat and the anterior chamber is not unusually shallow on slit-lamp examination. Plateau iris syndrome refers to the development of angle-closure, either spontaneously or after pupillary dilation, in an eye with plateau iris configuration despite the presence of a patent iridectomy or iridotomy. Some patients may develop acute angle-closure glaucoma[Godel, 1968 #196; Lowe, 1968 #197; Lowe, 1981 #198; Wand, 1977 #199] The risk of postoperative pupillary dilation after iridectomy or iridotomy is infrequently realized. Until recently, plateau iris syndrome was considered a rare entity. We have differentiated two subtypes.[Lowe, 1989 #2841] In the complete syndrome, which comprises the classic situation and is rare, intraocular pressure rises when the angle closes with pupillary dilation. In the incomplete syndrome, intraocular pressure does not change. The important factor differentiating the complete and incomplete syndromes is the level of the iris stroma with respect to the angle structures, or the "height" to which the plateau rises . If the angle closes to the upper trabecular meshwork or Schwalbe's line, intraocular pressure rises, whereas if the angle closes partially, leaving the upper portion of the filtering meshwork open, the pressure will not rise. This is a far more common situation and is clinically significant as these patients can develop PAS up to years after a successful iridotomy produces what appears as a well-opened angle. Plateau iris results from large and/or anteriorly positioned ciliary processes holding up the peripheral iris and maintaining its apposition to the trabecular meshwork ..[Pavlin, 1992 #240; Ritch, 1992 #1046; Wand, 1993 #3212] When indentation gonioscopy is performed in such an eye, the ciliary processes prevent posterior movement of the peripheral iris. As a result, a sinuous configuration results (sine wave sign), in which the iris follows the curvature of the lens, reaches its deepest point at the lens equator, then rises again over the ciliary processes before dropping peripherally. Much more force is needed during gonioscopy to open the angle than in pupillary block because the ciliary processes must be displaced, and the angle does not open as widely. In a morphometric study of the ciliary sulcus, Orgül et al.[Orgül, 1993 #2835] proposed that the displacement of the pars plicata from the peripheral iris to the iris root during embryogenesis may be incomplete in eyes of shorter axial length. Darkroom gonioscopy is important in plateau iris as well as in pupillary block, and an angle which appears open in the light can close in the dark. Patients with plateau iris tend to be female, younger (30s to 50s) and less hyperopic than those with relative pupillary block, and often have a family history of angle-closure glaucoma. Except in the rare younger patients (20s and 30s), some element of pupillary block is also present. However, because of the nature of the anatomic relationships of the structures surrounding the posterior chamber, the degree of relative pupillary block necessary to induce angle-closure is less than that in primary angle-closure glaucoma; this seems to account for the deeper anterior chamber and flatter iris surface in eyes with angle-closure and plateau iris. Patients with plateau iris who develop angle-closure glaucoma are also somewhat younger than those with pupillary block angle-closure glaucoma. As a general rule, the older the patient, the less prominent the angulation of the peripheral iris and the greater the element of pupillary block. Iridotomy is successful at opening the angle when a component of pupillary block is present, but periodic gonioscopy remains indicated, as the angle can narrow further with age due to enlargement of the lens. If plateau iris was not diagnosed before iridotomy and intraocular pressure is elevated postlaser, careful gonioscopy should be performed. If the angle is open, secondary damage to the trabecular meshwork or pigment liberation with dilation are the most likely causes. If the angle is closed, the differential diagnosis, besides plateau iris, should include malignant glaucoma, in which the anterior chamber is extremely shallow; PAS, which can be ruled out by indentation gonioscopy; or incomplete iridectomy. Although plateau iris syndrome is usually recognized in the postoperative period, it may develop years later. Patients with plateau iris configuration should not be assumed to be permanently cured, even though plateau iris syndrome does not develop immediately. IRIDOSCHISIS Iridoschisis is a separation of the anterior and posterior iris stromal layers which occurs primarily in older women. It is usually bilateral, but may be asymmetric. The amount of stromal separation can sometimes be dramatic. Iridoschisis has been associated in the literature with narrow angles and angle-closure glaucoma.[Romano, 1972 #203; Salmon, 1992 #8638; Loewenstein, 1948 #8969; Loewenstein, 1945 #8968; Haik, 1952 #8970; McCulloch, 1950 #8971; Mills, 1967 #8972; Rodrigues, 1983 #8973; Carter, 1953 #8974] Whether angle-closure requires an eye with a preexisting narrow angle is unknown. ANGLE-CLOSURE GLAUCOMAS ASSOCIATED WITH DRUGS AND OTHER DISORDERS Miotic-induced Angle-closure Glaucoma Prolonged miotic treatment in eyes with open-angle glaucoma and narrow angles may lead to pupillary block and angle-closure glaucoma. We have seen chronic angle-closure develop after several years of miotic therapy in eyes that initially had wide open angles. In some eyes, zonular relaxation occurs more readily than in others, so that anterior lens movement and an increase in axial lens thickness may facilitate pupillary block and angle-closure. In other eyes, there is little change in the lens, but progressively increasing pressure in the posterior chamber gradually pushes the peripheral iris against the trabecular meshwork. It is our impression that eyes with exfoliation syndrome are particularly prone to develop miotic-induced angle-closure. In these eyes, the iris is thicker and stiffer than normal due to deposition of exfoliation material within the stroma. In addition, zonular weakness allows the lens to move forward, leading to pupillary block. Less commonly, miotic therapy can have a pronounced effect on lens position and trigger malignant glaucoma.[Gorin, 1966 #625; Levene, 1972 #638; Merritt, 1977 #639; Rieser, 1972 #626] Unequal anterior chamber depths, a progressive increase in myopia, or progressive shallowing of the anterior chamber are clues to the correct diagnosis. Combined Mechanism Glaucoma Combined mechanism glaucoma refers to situations in which both open-angle and angle-closure components are present. A patient may have open-angle glaucoma and either narrow angles with superimposed intermittent angle-closure glaucoma or miotic-induced angle-closure. The most common situation is that in which angle-closure, either acute or chronic, is eliminated by iridotomy and/or iridoplasty and intraocular pressure still remains elevated, with or without the presence of PAS of any extent. Another situation occurs in eyes with exfoliation syndrome successfully treated for angle-closure glaucoma, in which open-angle glaucoma can develop independently years later with progressive blockage of the trabecular meshwork. In all of these cases, the residual open-angle component is treated as open-angle glaucoma. Mixed Mechanism Glaucoma This term is often used interchangeably with combined mechanism glaucoma, creating additional confusion. It is better to reserve this term to describe residual appositional angle-closure by another mechanism (plateau iris, phacomorphic, ciliary block) remaining after elimination of pupillary block with partial opening of the angle. Phacomorphic Glaucoma Swelling of the lens may convert an anterior chamber of medium depth into one that is markedly shallow and precipitate acute angle-closure glaucoma. In countries in which cataracts are prevalent and operations not readily available, acute angle-closure glaucoma from swollen hypermature lenses is common. Again, some element of pupillary block may also be present. Phacomorphic glaucoma is often unresponsive to medical therapy, and paradoxical reactions to pilocarpine are common. Pilocarpine, even in elderly patients, increases axial lens thickness and causes anterior lens movement, further shallowing the anterior chamber.[Abramson, 1973 #89] Slight lens subluxation in eyes of elderly patients, formerly termed senile subluxation of the lens, is most commonly associated with exfoliation syndrome. Mild iridodonesis may be seen. In some cases, anterior lens movement may be sufficient to cause angle-closure glaucoma, usually chronic. These eyes are more susceptible to the development of miotic-induced angle-closure during treatment for open-angle glaucoma. Iridotomy usually suffices to eliminate pupillary block and the angle-closure component. In younger patients anterior lens movement is often associated with secondary causes or ciliary block. After iridotomy, iridoplasty may be necessary to eliminate continued appositional closure if cycloplegics are unsuccessful at maintaining a more posterior lens position and an open angle. This topic is discussed more fully in Chapter 58. Malignant Glaucoma Malignant (ciliary block) glaucoma[Levene, 1972 #638; Shaffer, 1978 #640; Simmons, 1972 #641; Weiss, 1972 #642; Dueker, 1994 #4726] is a multifactorial disease in which the following components may play varying roles: (1) previous acute or chronic angle-closure glaucoma, (2) shallowness of the anterior chamber, (3) forward movement of the lens, (4) pupillary block by the lens or vitreous, (5) slackness of the zonules, (6) anterior rotation and/or swelling of the ciliary body, (7) thickening of the anterior hyaloid membrane, (8) expansion of the vitreous, and (9) posterior aqueous displacement into or behind the vitreous. This topic is covered in Chapter 39. Swelling or anterior rotation of the ciliary body with forward rotation of the lens-iris diaphragm and relaxation of the zonular apparatus causes anterior lens displacement which in turn causes direct angle-closure by physically pushing the iris agains the trabecular meshwork.[Phelps, 1974 #643] Accurate diagnosis and treatment are often more difficult when the initiating event is posterior to the lens-iris diaphragm. In predisposed eyes, miotic therapy can have a pronounced effect on lens position and trigger malignant glaucoma.[Gorin, 1966 #625; Levene, 1972 #638; Merritt, 1977 #639; Rieser, 1972 #626] Unequal anterior chamber depths, a progressive increase in myopia, or progressive shallowing of the anterior chamber are clues to the correct diagnosis. Malignant glaucoma may occur following cataract surgery with posterior chamber intraocular lens implantation.[Brown, 1986 #1255; Epstein, 1984 #1395; Lynch, 1986 #2773; Duy, 1987 #2729; Reed, 1990 #1054; Vajpayee, 1991 #2812; Tello, 1993 #1963] The differential diagnosis includes pupillary block, choroidal hemorrhage, and ciliochoroidal effusion with anterior rotation of the ciliary body and secondary angle closure. Shallowing of the central anterior chamber occurs in pseudophakic malignant glaucoma, but not in pupillary block. Rupture of the anterior hyaloid face is usually curative and allows aqueous to move into the anterior segment. We have examined several patients with presumed aqueous misdirection in whom an annular ciliary body detachment had caused anterior movement of the ciliary body. Whether a posterior diversion of aqueous flow is present in these disorders is unknown. Some of the disorders that can lead to this picture are covered in other chapters. These include drug sensitivity (e.g., sulfonamides, see Chapter 56); angle-closure after panretinal photocoagulation, central retinal vein occlusion, or scleral buckling procedures (see Chapters 50 and 51); uveal effusion from posterior segment inflammation; ciliary body swelling, inflammation, or cysts ; posterior segment tumors (see Chapter 52). Aphakic and pseudophakic malignant glaucoma are discussed in Chapter 61. Retinopathy of prematurity Angle-closure may occur in very young children with retinopathy of prematurity due to forward shifting of the lens-iris diaphragm (see also Chapter 44).[Cohen, 1964 #8926; Hittner, 1979 #1894; Pollard, 1980 #5292; McCormick, 1971 #1898; Laws, 1994 #8928; Kushner, 1982 #1057] These children do not respond to iridotomy. In young adults with this condition, there appears to be a superimposed element of pupillary block, and iridotomy may be successful.[Ueda, 1988 #8927; Smith, 1984 #1899] Nanophthalmos Nanophthalmos is a bilateral, often familial form of microphthalmos unaccompanied by other congenital malformations. It is characterized by hyperopia, small corneal diameter, thick sclera, and narrow angles.[O'Grady, 1971 #8231] Angle-closure glaucoma usually appears between the ages of 20 and 50 years. Although by definition, nanophthalmos refers to an eye of axial length less than 20 mm, there is obviously a gradient of hyperopic refraction, the degree of hyperopia correlating inversely with axial length. There is an inverse correlation between the degree of hyperopia and the age of onset of angle-closure. The youngest reported patient was 9 years old with 21 diopters of hyperopia.[Hatcher, 1952 #8962] However, acute angle-closure glaucoma can also develop in the elderly.[Cross, 1976 #8964] The sclera in nanophthalmic eyes is abnormally thick.[Brockhurst, 1975 #2710] Electron microscopy reveals disordered collagen bundles and fraying of collagen fibrils, with absence of elastic fibers.[Trelstad, 1982 #5595; Stewart, 1991 #2804] In tissue culture, scleral fibroblasts of eyes with nanophthalmos appear to have an abnormal glycosamine metabolism, which might explain the abnormal packing of collagen bundles and scleral thickening.[Shiono, 1992 #2798] Uveal effusion is common, either spontaneously or after surgical procedures, including filtration surgery or cataract extraction.[Brockhurst, 1975 #2710; Ryan, 1982 #8963] Associations with retinitis pigmentosa[Ghose, 1985 #8230; MacKay, 1987 #1042] and Hallerman-Streiff syndrome[Stewart, 1991 #2804] have been reported. Laser iridotomy for angle-closure is usually unsuccessful or only temporarily successful. If successful initially, lens enlargement with age can lead to appositional closure. Iridoplasty (gonioplasty) to flatten the peripheral iris was first reported in 1979 by Kimbrough et al.[Kimbrough, 1979 #1412] Combined iridotomy and iridoplasty often brings the angle-closure under control.[Jin, 1990 #2759] Uveal effusions have been reported after both laser iridotomy[Karjalainen, 1986 #1408] and trabeculoplasty.[Good, 1988 #2742] The risks of surgical intervention include malignant glaucoma, expulsive suprachoroidal hemorrhage, and retinal detachment.[Hyams, 1990 #8965] Posterior sclerotomy may or may not be successful at preventing uveal effusion.[Calhoun, 1975 #8047; Jin, 1990 #2759] Vortex vein decompression for nanophthalmic uveal effusion was described by Brockhurst,[Brockhurst, 1980 #5305] but the technique is technically difficult. Partial thickness sclerectomies and sclerostomies were reported in one patient to achieve complete resolution of retinal and choroidal detachments, suggesting impairment of transscleral protein transport as a primary pathophysiologic mechanism in nanophthalmic uveal effusion.[Allen, 1988 #1921] Subsequently, Wax et al. described success with anterior lamellar sclerectomy without sclerostomy.[Wax, 1992 #2820] CLINICAL PATHOLOGY OF ANGLE-CLOSURE GLAUCOMA When the angle totally occludes, aqueous outflow is blocked, and intraocular pressure rises markedly. The effect of the elevated pressure depends on the magnitude and rapidity of its rise. At the same time the pupillary reaction to direct light decreases. The pupil becomes partly dilated and tends to assume a vertically oval shape, but may be oblique or even horizontal. Cornea With very high intraocular pressure, corneal edema is severe. Transient loss of sensitivity can occur.[Patel, 1988 #2787] The cornea is cloudy and may be twice its usual thickness. Endothelial cell density is reduced by as much as 33% following an acute attack and is greater the longer the duration of the attack.[Bigar, 1982 #644; Mapstone, 1985 #121; Markowitz, 1984 #652; Brooks, 1991 #8958; Olsen, 1980 #3558; Malaise-Stals, 1984 #8959] Corneal decompensation may occur in eyes with preexisting endothelial compromise.[Krontz, 1988 #1932; Hyams, 1983 #8960] When the pressure is lowered, the edema clears first at the periphery. Folds in Descemet's membrane form. Following prolonged high pressure, corneal edema and striate keratopathy may persist for some days. With severe damage, chronic edema may persist, lipid is deposited, and the cornea may become fibrosed and vascularized. Iris Partial necrosis of the iris stroma is the first sign of damage from elevated intraocular pressure experimentally.[Anderson, 1975 #200] At pressures over 60 mmHg, the pupil becomes increasingly resistant to miotics, probably caused by direct pressure on the sphincter muscle.[Charles, 1970 #201] The sphincter may respond to miotics after the pressure has been lowered, but when intraocular pressure exceeds the diastolic blood pressure, the iris around the pupil becomes ischemic.[Charles, 1970 #201] The sphincter muscle then loses its ability to contract even if intraocular pressure is lowered, and patchy atrophy of the iris occurs. The dilator muscle is less affected than the sphincter, so that the instillation of 10% phenylephrine usually causes increased pupillary dilation. In the segments in which the stroma is not obviously atrophic, the pupillary margin is thick, rolled, and bunched with radial folds. At the margins of the atrophic area, the stromal fibers run obliquely to the periphery behind the edges of the atrophic area, thus producing a twisting of this border zone of the stroma[Winstanley, 1961 #202]. In severe and prolonged attacks, diffuse iris atrophy occurs. Sometimes a sector of the iris stroma will be disrupted and look like iridoschisis[Romano, 1972 #203]. This may occur with slow progressive atrophy months or years after the acute attack. The pigment epithelium and dilator muscle can be patchily affected and areas may transilluminate. Posterior synechiae may be minimal or extensive. After iridectomy aqueous humor flowing into the anterior chamber can bypass the pupil, favoring formation of postoperative posterior synechiae. Ciliary Body In 1973, Kerman et al.[Kerman, 1973 #645] reported that the ciliary processes may be inserted more anteriorly than normal and extend to the peripheral posterior iris in eyes with angle-closure. With the discovery that plateau iris is caused by large and/or anterior ciliary processes, it is now becoming evident that there is a spectrum of ciliary body size and position. The ciliary body itself does not appear to be adversely affected by acute angle-closure glaucoma. Lens Lens damage can occur as: (1) glaukomflecken, (2) anterior capsular cataract, (3) pigment deposition, posterior synechiae, and fibrosis, (4) cortical cataracts, and (5) nuclear sclerosis. Glaukomflecken ("glaucoma flakes"), or disseminated anterior subcapsular cataracts of acute glaucoma, are the most characteristic signs of lens damage from sudden severe rises of intraocular pressure. They are thought to be caused by pressure necrosis of anterior lens fibers and do not occur at the posterior pole. When intraocular pressure is very high, the lens damage simulates a thin, gray deposit of exudate on the lens surface.[Jones, 1959 #646] With a fall in pressure, the sheet becomes thinner in some places and more condensed in others. Holes develop within it, so it may appear as a coarse, irregular, white net.[Lowe, 1965 #647] Later these flakes become more discrete and appear as small, irregular, blue-white plaques. They tend to follow suture lines of the lens, suggesting necrosis of the tips of the lens fibers. Gradually, the flakes diminish and usually become relatively sparse. As new lens fibers grow from the equator, they overlie the flecks, which sink deeper into the lens and persist as permanent evidence. Glaukomflecken occur almost entirely within the pupil according to its size at the time of the attack.[Sugar, 1946 #648] Glaukomflecken are rare apart from acute angle-closure glaucoma, but have been seen after contusion and chemical burns and also when the anterior chamber has remained flat postoperatively with the cornea and lens in contact for some days. Occasionally, small white plaques resembling glaukomflecken may persist in the anterior surface of the lens. These are anterior capsular cataracts. Anterior cortical lens opacities commonly follow severe attacks of angle-closure glaucoma and may persist as faint irregular streaks that almost invariably progress. The first sign of nuclear sclerosis is a myopic refractive change, which may stabilize or progress. Following severe glaucomatous iritis with extensive posterior synechiae, fibrosis may extend from the iris onto the anterior lens surface. Zonules The zonules can be damaged, so with surgery the lens may move forward with the development of malignant (ciliary block) glaucoma. Occasionally, the opaque lens may slowly dislocate over the years and sink below the pupil. Choroid Kubota et al.[Kubota, 1993 #2833] reported decreased choroidal thickness in 12 eyes with angle-closure glaucoma associated with malignant melanoma of the ciliary body. The decreased thickness was primarily due to decreased choroidal vessel diameter, suggesting decreased choroidal perfusion. Retina and Optic Nerve In intermittent angle-closure glaucoma, even after many attacks, the optic disc is typically unaffected. During the initial states of an acute attack, the disc may appear normal, congested, or edematous with retinal venous congestion and retinal hemorrhages near the disc. When intraocular pressure is acutely elevated in owl monkeys, damage to the nerve fiber layer and ganglion cells precedes damage to most other tissues except the iris.[Anderson, 1975 #200] Douglas et al.[Douglas, 1975 #204] found pallor without cupping following acute attacks, and pallor and cupping in patients with chronic angle-closure. Acutely elevated intraocular pressure in monkeys leads to optic disc congestion lasting several days before pallor and cupping develop.[Zimmerman, 1967 #650] Large retinal hemorrhages near the disc can occur with sudden lowering of intraocular pressure as after hyperosmotic or carbonic anhydrase inhibitor therapy. Retinal function is depressed with raised intraocular pressure.[Uenoyama, 1969 #649] Abnormalities of visual evoked potentials have been reported.[Mitchell, 1989 #1906] In a histological study of 21 eyes with secondary angle-closure glaucoma, Jonas et al.[Jonas, 1992 #1051] found the lamina cribrosa significantly thinner, the optic cup deeper and wider, and the corpora amylacea count lower than in controls. Parapapillary atrophy was significantly greater and occurred more frequently in glaucomatous eyes and the parapapillary retina was significantly thinner.[Jonas, 1992 #1052] A significantly decreased photoreceptor, but not retinal pigment epithelial, cell count was reported in eyes with angle-closure following penetrating trauma.[Panda, 1992 #2786] The final effects will depend on severity and duration of the attack. Recovery may be complete or there may be contraction of isopters and nerve fiber bundle defects.[Douglas, 1975 #204; Lowe, 1973 #624] Pallor without cupping was found to be characteristic of discs after acute angle-closure glaucoma, whereas both pallor and cupping occurred in chronic angle-closure.[Douglas, 1975 #204] In prolonged attacks, when treatment is delayed, glaucomatous damage may progress to the point at which vision is reduced to perception of hand movements or light. In chronic angle-closure glaucoma, the visual field defects and optic disc cupping progress similarly to those of open-angle glaucoma. |
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From: Ray Bonar )
Subject: Angle-closure Glaucoma - Clinical types Date: 1997/12/27 Angle-closure Glaucoma - Clinical types Robert Ritch Ronald F. Lowe The nomenclature for the various clinically distinct types and modes of presentation of angle-closure glaucoma has been inconsistently used by different investigators, by investigators in different countries, and at different points in time. As a result, there is a moderate amount of confusion regarding terminology. This pertains in particular to the terms intermittent, prodromal, and subacute; chronic and creeping; and combined mechanism versus mixed mechanism. Angle-closure glaucoma has long been divided by convention into "primary" and "secondary" forms. Primary angle-closure, or relative pupillary block, is the most common mechanism of angle-closure glaucoma and studies of series of patients with acute angle-closure have been based on this concept. It should be recognized that publications dealing with characteristics of patients with "angle-closure glaucoma" include not only relative pupillary block but other mechanisms as well. However, because relative pupillary block forms the greatest proportion, the data should be regarded as not inordinately skewed. PRESENTATION Angle-closure glaucoma can present with a spectrum of symptomatology, from none at all to severe pain, blurred vision, and nausea. The terminology is based upon the signs and symptoms at the time of diagnosis, and these should not be though of as specific "types" of angle-closure, but merely descriptive phenomena which may vary with time in any individual patient (see Fig. 38-1). For example, a patient with a narrow angle and peripheral anterior synechiae (chronic angle-closure) may have symptoms of intermittent angle-closure attacks which, if not detected or diagnosed, can later present as acute angle-closure glaucoma. The mode of presentation depends on a combination of the percentage of the filtering meshwork occluded by the iris, the rapidity with which the occlusion occurs, and the ease of reversal of the iridotrabecular block. Fourman[Fourman, 1989 #2738] has published a useful flow chart to aid the ophthalmologist in dealing with acute angle-closure glaucoma. Intermittent angle-closure Intermittent angle-closure defines repeated, brief episodes of angle-closure with mild symptoms and elevated intraocular pressure. These resolve spontaneously and ocular function is normal between attacks. Intermittent angle-closure is often a prelude to acute angle-closure. The intraocular pressure is high enough to cause symptoms, but not as high as in a full-blown attack. This may be due to partial angle-closure, which could affect more the narrower superior part of the angle,[Leighton, 1971 #184] or 360° of closure with just enough functioning meshwork remaining above the level of closure to allow some aqueous to escape, or perhaps to a freely reactive pupil, which allows spontaneous reversal of the symptoms once the triggering element is removed. Intermittent attacks are most commonly associated with fatigue, dim light, and using the eyes for near work (see Table 38-1). They tend to recur under similar circumstances and at about the same time of day or evening. The symptoms are a dull ache in or around one eye and mildly blurred vision. Halos around lights are often not seen unless the patient is outdoors. Haloes are believed to result from stretching of the corneal lamellae, causing the cornea to act as a diffraction grating, producing a blue-green central halo and a yellow-red peripheral one. Halos that are seen every night are caused by cataracts, corneal disease, or persistently high intraocular pressure. Transient monocular visual loss has also been noted.[Ravitz, 1984 #185] The patient may recognize the cause and avoid or reduce the activity, such as watching television or reading. The attacks last for about a half hour after cessation of the inciting activity. Sleep is so often recognized as beneficial that many patients go to bed early or take a nap to obtain relief. Amelioration of the attack is attributed to sleep-induced miosis and possibly to decreased intraocular pressure resulting from decreased aqueous humor secretion.[Reiss, 1984 #186] If the symptoms persist overnight, a true attack has developed. Initially, intermittent attacks occur at intervals of weeks or months, but eventually may occur almost nightly. They may continue uneventfully for months or years. Usually only one eye is involved, but bilateral attacks can occur. Because the eyes appear normal between attacks except for a narrow angle, the diagnosis is frequently missed, and even ophthalmologists may be misled by the patient's self-diagnosis of migraine, sinusitis, anxiety or eyestrain. Examination reveals shallow anterior chambers, iris bombé, narrow angles, and sometimes an enlarged or oval pupil. Provocative testing may result in angle-closure, elevated intraocular pressure, and reproduction of the patient's symptoms. The end result of intermittent angle-closure glaucoma usually differs between whites and races with thick, heavily pigmented irides. In whites the attacks are essentially benign and may recur for years without causing damage. Attacks may be accompanied by progressive PAS formation, leading to chronic angle-closure. The greatest danger lies in the possibility of sudden conversion to acute angle-closure glaucoma. Laser iridotomy is definitive if the eye is otherwise normal and the angle not occludable by mechanisms other than pupillary block. In Asians the history may be consistent with intermittent angle-closure glaucoma, but the intraocular pressure is often elevated and the angle variably closed by PAS, depending on the frequency and severity of the attacks. Asian eyes are more prone to "creeping" angle-closure and PAS formation. Iridotomy alone may be insufficient to control intraocular pressure. Blacks also have a greater tendency to develop chronic angle-closure, but it is our impression that the anterior chambers are often deeper than those of Asians and that iris bombé is much less frequent. Both intermittent and acute attacks are less common in blacks than in Asians. Comparative biometric studies would greatly help to increase our understanding of angle-closure in these groups. Subacute angle-closure glaucoma Subacute angle-closure describes a stage in which attacks may be more frequent and prolonged than in intermittent angle-closure, but less so than in acute angle-closure. At least in some cases, this is caused by less than total closure of the angle.[Chandler, 1955 #187] Symptoms of blurred vision, pain, and halos may be more marked than in intermittent angle-closure. Attacks may occur over months or years, finally leading to an acute attack. Subacute attacks are much more common in Asians than in whites and can cause severe damage without much inflammation. They tend to produce a chronically dilated pupil, mild iris atrophy, PAS, and pigment on the iris close to the inferior angle. Intraocular pressure levels and glaucomatous disc and visual field damage vary according to the severity and duration of the attacks. Acute Angle-closure Glaucoma Precipitating events Acute angle-closure glaucoma can lead to irreversible damage. Various stimuli may trigger an attack. Most attacks occur during the evening, beginning mildly and rapidly increasing in severity. Approximately one-third of patients describe episodes of intermittent or subacute angle-closure having occurred before the acute attack. The physiological factors that convert relative pupillary block to absolute pupillary block remain poorly understood, as are those that determine whether an eye will develop acute or chronic angle-closure. Although pupillary block is the common underlying mechanism, the course of the disease depends on the degree and suddenness of the block, the flaccidity and physiologic responses of the iris, and the width and depth of the anterior chamber angle. Absolute pupillary block is most commonly triggered when the pupil is middilated, about 3.5 to 6 mm in diameter.[Chandler, 1952 #105] In this position, the combination of pupillary block and relaxation of the peripheral iris, allowing its forward displacement into the anterior chamber, are maximal. Mapstone[Mapstone, 1968 #127] concluded that the posteriorly directed forces of the dilator and sphincter muscles and the stretching force of the sphincter during contraction are greatest when the pupil is middilated. The most common precipitating events include illness, emotional stress, trauma, intense concentration, and pharmacologic pupillary dilation.[Sugar, 1941 #116; Lowe, 1961 #8957] The role of emotional stress in inducing acute angle-closure should not be underestimated.[Inman, 1929 #190; Egan, 1955 #189; Cross, 1960 #188] A memorable example was a patient who, after narrowly missing being injured by a grenade thrown through his living room window as an expression of some differences of opinion, immediately developed bilateral attacks. Attacks rarely begin simultaneously in both eyes. Minor differences in anterior chamber depth almost invariably result in the eye with the shallower chamber being involved first. A multitude of other inciting factors have been presented in case reports, including acute infectious disorders, acquired immunodeficiency syndrome, tumors, and trauma. In many of these cases, the mechanism either has not been delineated or the block is posterior to the lens, due to uveal effusion. Symptoms and signs The symptoms of an acute attack result from the sudden, marked elevation of intraocular pressure to as high as 80 mmHg. Corneal edema results in blurred vision and intense pain and, secondarily, in lacrimation and lid edema. These, in combination with anxiety and fatigue, lead to nausea and vomiting, whereas vasovagal responses cause bradycardia and diaphoresis. Systemic symptoms may be so severe as to mislead the nonophthalmologist, and some patients have actually undergone unwarranted exploratory laparotomy. We saw one patient whose ataxia, blurred vision, and diagnosis of multiple sclerosis disappeared after laser iridotomy. The diagnosis is usually straightforward (Fig. 38-2). Central visual acuity is reduced and the intraocular pressure is markedly elevated. The lids are swollen and there is conjunctival hyperemia and circumcorneal injection. The cornea is edematous and the pupil usually middilated and vertically oval because of iris sphincter ischemia. The anterior chamber is shallow but usually formed centrally, whereas the midperipheral iris is bowed anteriorly and may touch the cornea peripherally. An inflammatory reaction is present in the anterior chamber. Hypopyon can occur in severe or prolonged attacks.[Zhang, 1984 #8961; Friedman, 1972 #8966] Corneal edema may initially limit gonioscopic and posterior segment examination, even after the topical application of glycerin. Inability to open the angle with indentation gonioscopy at this stage does not mean that the angle will remain sealed after iridotomy, nor does it accurately reflect the presence or extent of PAS. Examination of the opposite eye is particularly useful in differentiating acute angle-closure glaucoma from neovascular, uveitic or phacolytic glaucoma, and usually reveals a shallow anterior chamber and narrow angle. The optic nerve head may be hyperemic and edematous early in the attack. With prolonged attacks or cases in which unrecognized chronic angle-closure glaucoma precedes an acute attack, pallor and cupping, along with visual field damage, may be present. Central retinal vein occlusion may occur as a result of an acute attack[Tornquist, 1958 #195; Sonty, 1981 #2801] or may precipitate one.[Bloome, 1977 #630; Grant, 1973 #631; Hyams, 1972 #632; Mendelsohn, 1985 #633; Weber, 1987 #634; Segal, 1986 #2796] Visual field changes associated with acute pressure elevation usually show nonspecific generalized or upper field constriction.[McNaught, 1974 #191] Early loss of central vision, enlargement of the blind spot, and nerve fiber bundle defects may be found.[Douglas, 1975 #204; Horie, 1975 #635] After normalization of intraocular pressure, the visual fields may also normalize, or patients may be left with reduced color vision, generalized decreased sensitivity, or specific defects. These may be exaggerated by cataract formation or progression. An attack may terminate spontaneously if iris atrophy from tissue necrosis allows aqueous humor to percolate through the iris stroma, equivalent functionally to a spontaneous iridotomy.(Fig. 38-4) However, this occurs more frequently as a result of suppression of aqueous secretion by the high pressure. Spontaneous termination may also be facilitated by a change in the position of the lens-iris contact, or segmental iris constriction with peaking of the pupil.[Phillips, 1963 #192] Chronic Angle-closure Glaucoma Chronic angle-closure refers to an eye in which portions of the anterior chamber angle are permanently closed by PAS. Variable and sometimes conflicting terminology has been used to describe somewhat differently appearing forms. The approach to therapy is similar in all of them. The terminology used in this section is an attempt to differentiate the two pathways by which chronic angle-closure can develop. In the first, iris bombé from relative pupillary block may appositionally close the angle. Prolonged apposition or repeated subacute attacks lead to gradual PAS formation. These usually begin in the superior angle, which is narrower than the inferior angle,[Bhargava, 1973 #142; Mapstone, 1977 #636] as pinpoint synechiae reaching to the midtrabecular meshwork and then gradually expanding in width. In early cases, in which appositional closure is present but PAS have not yet formed, we prefer the term chronic appositional closure. This condition can lead to elevated intraocular pressure and glaucomatous disc and visual field damage without PAS formation.[Foulds, 1957 #637] Eyes with progressive PAS formation may eventually develop an acute attack of angle-closure when pupillary block results in closure of the remaining portions of the angle unaffected by PAS. Many cases, however, develop elevated intraocular pressure and glaucomatous damage in the absence of symptoms. The presentation is similar to that of open-angle glaucoma, with progression of glaucomatous cupping and visual field loss. This is the situation most commonly associated in the United States with chronic angle-closure glaucoma. However, eyes with the same appearance but normal intraocular pressure merely constitute an earlier stage. PAS may also form during an acute attack, remaining after iridotomy has opened the unaffected portions of the angle. These PAS are usually high and broad. When first observed at this stage, it is impossible to determine whether the PAS formed before or during the attack, or at both times. In eyes with darker irides, a second mechanism of progressive angle-closure is more common. The closure is circumferential and begins in the deepest portion of the angle. Closure occurs more evenly in all quadrants, so that the angle progressively becomes more shallow. The appearance over time is of a progressively more anterior iris insertion. Lowe[Lowe, 1964 #194] has termed this creeping angle-closure. The PAS gradually creep up the ciliary face to the scleral spur and then to the trabecular meshwork. Insertion of the iris at or anterior to the scleral spur is rare in young individuals, and in many eyes with angle-closure glaucoma that have such an insertion, creeping angle-closure is the underlying reason. Creeping angle-closure is uncommon in whites but much more prevalent in Asians, in whom it ranks high as a cause of blindness. Black patients with angle-closure also tend to have this form. It occurs in eyes with slightly deeper, though still shallow, anterior chambers than are found in acute angle-closure. The gradual shortening of the angle in the presence of iris bombé brings the peripheral iris close to the external angle wall more and more anteriorly, narrowing the gap between the iris and the trabecular meshwork. Eventually, an acute attack may supervene (more commonly in Asians), or the PAS may permanently occlude the trabecular meshwork and lead to elevated intraocular pressure and glaucomatous damage (more commonly in black patients). The intraocular pressure in eyes with chronic angle-closure may be normal or elevated. As PAS formation progresses in the absence of intermittent attacks, the pressure rises gradually as less and less functional trabecular meshwork becomes available. In eyes with intermittent attacks, the pressure rises more rapidly relative to the extent of PAS formation caused by recurrent damage to the trabecular meshwork by the transient angle-closure. Dispersed pigment granules collect in the iridocorneal angle where the peripheral iris is in contact with the cornea. Dense blotches of pigment on the meshwork, particularly in the superior angle, or deposits of black pigment in the angle of a lightly pigmented iris, are highly suggestive of previous appositional closure. If the angle opens, this deposited line of pigment shows the extent of previous angle closure and can sometimes be a helpful diagnostic feature. The anterior chamber is quiet and usually deeper than in eyes with acute angle-closure glaucoma. The pupil is normal. The gradual elevation of intraocular pressure does not result in corneal endothelial decompensation, and edema is rare. The intraocular pressure is usually less than 40 mmHg and does not reach the levels found in acute angle-closure glaucoma. Symptoms are absent until the pressure rises high enough to affect the cornea or until extensive visual field damage has occurred. Although iridotomy will eliminate the pupillary block, intraocular pressure often remains elevated, and further medical treatment or surgery is required. Absolute Glaucoma Absolute glaucoma refers to an eye with no light perception and a persistently elevated intraocular pressure. The angle initially may be open or closed, but in phakic eyes an intumescent cataract often develops and leads to an associated angle-closure. The time required for a neglected angle-closure attack to cause total blindness is variable and depends on the severity of the acute attack, but appears to be an average of 1 to 2 years. Treatment is palliative and intraocular surgery is unwarranted. If corneal edema and pain are not relieved by topical beta-adrenergic blocking agents, steroids, and cycloplegics, noninvasive cycloablation may be performed. If this is insufficient or if complications such as phacolytic glaucoma develop, evisceration or enucleation may be necessary. Phthisis bulbi is not an uncommon outcome. PLATEAU IRIS Plateau iris configuration refers to the anatomic structure in which the iris root angulates forward and then centrally.[Tornquist, 1958 #195] In many cases, the iris root is short and is inserted anteriorly on the ciliary face, so that the angle is shallow and narrow, with a sharp drop-off of the peripheral iris at the inner aspect of the angle. The iris surface appears flat and the anterior chamber is not unusually shallow on slit-lamp examination. Plateau iris syndrome refers to the development of angle-closure, either spontaneously or after pupillary dilation, in an eye with plateau iris configuration despite the presence of a patent iridectomy or iridotomy. Some patients may develop acute angle-closure glaucoma[Godel, 1968 #196; Lowe, 1968 #197; Lowe, 1981 #198; Wand, 1977 #199] The risk of postoperative pupillary dilation after iridectomy or iridotomy is infrequently realized. Until recently, plateau iris syndrome was considered a rare entity. We have differentiated two subtypes.[Lowe, 1989 #2841] In the complete syndrome, which comprises the classic situation and is rare, intraocular pressure rises when the angle closes with pupillary dilation. In the incomplete syndrome, intraocular pressure does not change. The important factor differentiating the complete and incomplete syndromes is the level of the iris stroma with respect to the angle structures, or the "height" to which the plateau rises . If the angle closes to the upper trabecular meshwork or Schwalbe's line, intraocular pressure rises, whereas if the angle closes partially, leaving the upper portion of the filtering meshwork open, the pressure will not rise. This is a far more common situation and is clinically significant as these patients can develop PAS up to years after a successful iridotomy produces what appears as a well-opened angle. Plateau iris results from large and/or anteriorly positioned ciliary processes holding up the peripheral iris and maintaining its apposition to the trabecular meshwork ..[Pavlin, 1992 #240; Ritch, 1992 #1046; Wand, 1993 #3212] When indentation gonioscopy is performed in such an eye, the ciliary processes prevent posterior movement of the peripheral iris. As a result, a sinuous configuration results (sine wave sign), in which the iris follows the curvature of the lens, reaches its deepest point at the lens equator, then rises again over the ciliary processes before dropping peripherally. Much more force is needed during gonioscopy to open the angle than in pupillary block because the ciliary processes must be displaced, and the angle does not open as widely. In a morphometric study of the ciliary sulcus, Orgül et al.[Orgül, 1993 #2835] proposed that the displacement of the pars plicata from the peripheral iris to the iris root during embryogenesis may be incomplete in eyes of shorter axial length. Darkroom gonioscopy is important in plateau iris as well as in pupillary block, and an angle which appears open in the light can close in the dark. Patients with plateau iris tend to be female, younger (30s to 50s) and less hyperopic than those with relative pupillary block, and often have a family history of angle-closure glaucoma. Except in the rare younger patients (20s and 30s), some element of pupillary block is also present. However, because of the nature of the anatomic relationships of the structures surrounding the posterior chamber, the degree of relative pupillary block necessary to induce angle-closure is less than that in primary angle-closure glaucoma; this seems to account for the deeper anterior chamber and flatter iris surface in eyes with angle-closure and plateau iris. Patients with plateau iris who develop angle-closure glaucoma are also somewhat younger than those with pupillary block angle-closure glaucoma. As a general rule, the older the patient, the less prominent the angulation of the peripheral iris and the greater the element of pupillary block. Iridotomy is successful at opening the angle when a component of pupillary block is present, but periodic gonioscopy remains indicated, as the angle can narrow further with age due to enlargement of the lens. If plateau iris was not diagnosed before iridotomy and intraocular pressure is elevated postlaser, careful gonioscopy should be performed. If the angle is open, secondary damage to the trabecular meshwork or pigment liberation with dilation are the most likely causes. If the angle is closed, the differential diagnosis, besides plateau iris, should include malignant glaucoma, in which the anterior chamber is extremely shallow; PAS, which can be ruled out by indentation gonioscopy; or incomplete iridectomy. Although plateau iris syndrome is usually recognized in the postoperative period, it may develop years later. Patients with plateau iris configuration should not be assumed to be permanently cured, even though plateau iris syndrome does not develop immediately. IRIDOSCHISIS Iridoschisis is a separation of the anterior and posterior iris stromal layers which occurs primarily in older women. It is usually bilateral, but may be asymmetric. The amount of stromal separation can sometimes be dramatic. Iridoschisis has been associated in the literature with narrow angles and angle-closure glaucoma.[Romano, 1972 #203; Salmon, 1992 #8638; Loewenstein, 1948 #8969; Loewenstein, 1945 #8968; Haik, 1952 #8970; McCulloch, 1950 #8971; Mills, 1967 #8972; Rodrigues, 1983 #8973; Carter, 1953 #8974] Whether angle-closure requires an eye with a preexisting narrow angle is unknown. ANGLE-CLOSURE GLAUCOMAS ASSOCIATED WITH DRUGS AND OTHER DISORDERS Miotic-induced Angle-closure Glaucoma Prolonged miotic treatment in eyes with open-angle glaucoma and narrow angles may lead to pupillary block and angle-closure glaucoma. We have seen chronic angle-closure develop after several years of miotic therapy in eyes that initially had wide open angles. In some eyes, zonular relaxation occurs more readily than in others, so that anterior lens movement and an increase in axial lens thickness may facilitate pupillary block and angle-closure. In other eyes, there is little change in the lens, but progressively increasing pressure in the posterior chamber gradually pushes the peripheral iris against the trabecular meshwork. It is our impression that eyes with exfoliation syndrome are particularly prone to develop miotic-induced angle-closure. In these eyes, the iris is thicker and stiffer than normal due to deposition of exfoliation material within the stroma. In addition, zonular weakness allows the lens to move forward, leading to pupillary block. Less commonly, miotic therapy can have a pronounced effect on lens position and trigger malignant glaucoma.[Gorin, 1966 #625; Levene, 1972 #638; Merritt, 1977 #639; Rieser, 1972 #626] Unequal anterior chamber depths, a progressive increase in myopia, or progressive shallowing of the anterior chamber are clues to the correct diagnosis. Combined Mechanism Glaucoma Combined mechanism glaucoma refers to situations in which both open-angle and angle-closure components are present. A patient may have open-angle glaucoma and either narrow angles with superimposed intermittent angle-closure glaucoma or miotic-induced angle-closure. The most common situation is that in which angle-closure, either acute or chronic, is eliminated by iridotomy and/or iridoplasty and intraocular pressure still remains elevated, with or without the presence of PAS of any extent. Another situation occurs in eyes with exfoliation syndrome successfully treated for angle-closure glaucoma, in which open-angle glaucoma can develop independently years later with progressive blockage of the trabecular meshwork. In all of these cases, the residual open-angle component is treated as open-angle glaucoma. Mixed Mechanism Glaucoma This term is often used interchangeably with combined mechanism glaucoma, creating additional confusion. It is better to reserve this term to describe residual appositional angle-closure by another mechanism (plateau iris, phacomorphic, ciliary block) remaining after elimination of pupillary block with partial opening of the angle. Phacomorphic Glaucoma Swelling of the lens may convert an anterior chamber of medium depth into one that is markedly shallow and precipitate acute angle-closure glaucoma. In countries in which cataracts are prevalent and operations not readily available, acute angle-closure glaucoma from swollen hypermature lenses is common. Again, some element of pupillary block may also be present. Phacomorphic glaucoma is often unresponsive to medical therapy, and paradoxical reactions to pilocarpine are common. Pilocarpine, even in elderly patients, increases axial lens thickness and causes anterior lens movement, further shallowing the anterior chamber.[Abramson, 1973 #89] Slight lens subluxation in eyes of elderly patients, formerly termed senile subluxation of the lens, is most commonly associated with exfoliation syndrome. Mild iridodonesis may be seen. In some cases, anterior lens movement may be sufficient to cause angle-closure glaucoma, usually chronic. These eyes are more susceptible to the development of miotic-induced angle-closure during treatment for open-angle glaucoma. Iridotomy usually suffices to eliminate pupillary block and the angle-closure component. In younger patients anterior lens movement is often associated with secondary causes or ciliary block. After iridotomy, iridoplasty may be necessary to eliminate continued appositional closure if cycloplegics are unsuccessful at maintaining a more posterior lens position and an open angle. This topic is discussed more fully in Chapter 58. Malignant Glaucoma Malignant (ciliary block) glaucoma[Levene, 1972 #638; Shaffer, 1978 #640; Simmons, 1972 #641; Weiss, 1972 #642; Dueker, 1994 #4726] is a multifactorial disease in which the following components may play varying roles: (1) previous acute or chronic angle-closure glaucoma, (2) shallowness of the anterior chamber, (3) forward movement of the lens, (4) pupillary block by the lens or vitreous, (5) slackness of the zonules, (6) anterior rotation and/or swelling of the ciliary body, (7) thickening of the anterior hyaloid membrane, (8) expansion of the vitreous, and (9) posterior aqueous displacement into or behind the vitreous. This topic is covered in Chapter 39. Swelling or anterior rotation of the ciliary body with forward rotation of the lens-iris diaphragm and relaxation of the zonular apparatus causes anterior lens displacement which in turn causes direct angle-closure by physically pushing the iris agains the trabecular meshwork.[Phelps, 1974 #643] Accurate diagnosis and treatment are often more difficult when the initiating event is posterior to the lens-iris diaphragm. In predisposed eyes, miotic therapy can have a pronounced effect on lens position and trigger malignant glaucoma.[Gorin, 1966 #625; Levene, 1972 #638; Merritt, 1977 #639; Rieser, 1972 #626] Unequal anterior chamber depths, a progressive increase in myopia, or progressive shallowing of the anterior chamber are clues to the correct diagnosis. Malignant glaucoma may occur following cataract surgery with posterior chamber intraocular lens implantation.[Brown, 1986 #1255; Epstein, 1984 #1395; Lynch, 1986 #2773; Duy, 1987 #2729; Reed, 1990 #1054; Vajpayee, 1991 #2812; Tello, 1993 #1963] The differential diagnosis includes pupillary block, choroidal hemorrhage, and ciliochoroidal effusion with anterior rotation of the ciliary body and secondary angle closure. Shallowing of the central anterior chamber occurs in pseudophakic malignant glaucoma, but not in pupillary block. Rupture of the anterior hyaloid face is usually curative and allows aqueous to move into the anterior segment. We have examined several patients with presumed aqueous misdirection in whom an annular ciliary body detachment had caused anterior movement of the ciliary body. Whether a posterior diversion of aqueous flow is present in these disorders is unknown. Some of the disorders that can lead to this picture are covered in other chapters. These include drug sensitivity (e.g., sulfonamides, see Chapter 56); angle-closure after panretinal photocoagulation, central retinal vein occlusion, or scleral buckling procedures (see Chapters 50 and 51); uveal effusion from posterior segment inflammation; ciliary body swelling, inflammation, or cysts ; posterior segment tumors (see Chapter 52). Aphakic and pseudophakic malignant glaucoma are discussed in Chapter 61. Retinopathy of prematurity Angle-closure may occur in very young children with retinopathy of prematurity due to forward shifting of the lens-iris diaphragm (see also Chapter 44).[Cohen, 1964 #8926; Hittner, 1979 #1894; Pollard, 1980 #5292; McCormick, 1971 #1898; Laws, 1994 #8928; Kushner, 1982 #1057] These children do not respond to iridotomy. In young adults with this condition, there appears to be a superimposed element of pupillary block, and iridotomy may be successful.[Ueda, 1988 #8927; Smith, 1984 #1899] Nanophthalmos Nanophthalmos is a bilateral, often familial form of microphthalmos unaccompanied by other congenital malformations. It is characterized by hyperopia, small corneal diameter, thick sclera, and narrow angles.[O'Grady, 1971 #8231] Angle-closure glaucoma usually appears between the ages of 20 and 50 years. Although by definition, nanophthalmos refers to an eye of axial length less than 20 mm, there is obviously a gradient of hyperopic refraction, the degree of hyperopia correlating inversely with axial length. There is an inverse correlation between the degree of hyperopia and the age of onset of angle-closure. The youngest reported patient was 9 years old with 21 diopters of hyperopia.[Hatcher, 1952 #8962] However, acute angle-closure glaucoma can also develop in the elderly.[Cross, 1976 #8964] The sclera in nanophthalmic eyes is abnormally thick.[Brockhurst, 1975 #2710] Electron microscopy reveals disordered collagen bundles and fraying of collagen fibrils, with absence of elastic fibers.[Trelstad, 1982 #5595; Stewart, 1991 #2804] In tissue culture, scleral fibroblasts of eyes with nanophthalmos appear to have an abnormal glycosamine metabolism, which might explain the abnormal packing of collagen bundles and scleral thickening.[Shiono, 1992 #2798] Uveal effusion is common, either spontaneously or after surgical procedures, including filtration surgery or cataract extraction.[Brockhurst, 1975 #2710; Ryan, 1982 #8963] Associations with retinitis pigmentosa[Ghose, 1985 #8230; MacKay, 1987 #1042] and Hallerman-Streiff syndrome[Stewart, 1991 #2804] have been reported. Laser iridotomy for angle-closure is usually unsuccessful or only temporarily successful. If successful initially, lens enlargement with age can lead to appositional closure. Iridoplasty (gonioplasty) to flatten the peripheral iris was first reported in 1979 by Kimbrough et al.[Kimbrough, 1979 #1412] Combined iridotomy and iridoplasty often brings the angle-closure under control.[Jin, 1990 #2759] Uveal effusions have been reported after both laser iridotomy[Karjalainen, 1986 #1408] and trabeculoplasty.[Good, 1988 #2742] The risks of surgical intervention include malignant glaucoma, expulsive suprachoroidal hemorrhage, and retinal detachment.[Hyams, 1990 #8965] Posterior sclerotomy may or may not be successful at preventing uveal effusion.[Calhoun, 1975 #8047; Jin, 1990 #2759] Vortex vein decompression for nanophthalmic uveal effusion was described by Brockhurst,[Brockhurst, 1980 #5305] but the technique is technically difficult. Partial thickness sclerectomies and sclerostomies were reported in one patient to achieve complete resolution of retinal and choroidal detachments, suggesting impairment of transscleral protein transport as a primary pathophysiologic mechanism in nanophthalmic uveal effusion.[Allen, 1988 #1921] Subsequently, Wax et al. described success with anterior lamellar sclerectomy without sclerostomy.[Wax, 1992 #2820] CLINICAL PATHOLOGY OF ANGLE-CLOSURE GLAUCOMA When the angle totally occludes, aqueous outflow is blocked, and intraocular pressure rises markedly. The effect of the elevated pressure depends on the magnitude and rapidity of its rise. At the same time the pupillary reaction to direct light decreases. The pupil becomes partly dilated and tends to assume a vertically oval shape, but may be oblique or even horizontal. Cornea With very high intraocular pressure, corneal edema is severe. Transient loss of sensitivity can occur.[Patel, 1988 #2787] The cornea is cloudy and may be twice its usual thickness. Endothelial cell density is reduced by as much as 33% following an acute attack and is greater the longer the duration of the attack.[Bigar, 1982 #644; Mapstone, 1985 #121; Markowitz, 1984 #652; Brooks, 1991 #8958; Olsen, 1980 #3558; Malaise-Stals, 1984 #8959] Corneal decompensation may occur in eyes with preexisting endothelial compromise.[Krontz, 1988 #1932; Hyams, 1983 #8960] When the pressure is lowered, the edema clears first at the periphery. Folds in Descemet's membrane form. Following prolonged high pressure, corneal edema and striate keratopathy may persist for some days. With severe damage, chronic edema may persist, lipid is deposited, and the cornea may become fibrosed and vascularized. Iris Partial necrosis of the iris stroma is the first sign of damage from elevated intraocular pressure experimentally.[Anderson, 1975 #200] At pressures over 60 mmHg, the pupil becomes increasingly resistant to miotics, probably caused by direct pressure on the sphincter muscle.[Charles, 1970 #201] The sphincter may respond to miotics after the pressure has been lowered, but when intraocular pressure exceeds the diastolic blood pressure, the iris around the pupil becomes ischemic.[Charles, 1970 #201] The sphincter muscle then loses its ability to contract even if intraocular pressure is lowered, and patchy atrophy of the iris occurs. The dilator muscle is less affected than the sphincter, so that the instillation of 10% phenylephrine usually causes increased pupillary dilation. In the segments in which the stroma is not obviously atrophic, the pupillary margin is thick, rolled, and bunched with radial folds. At the margins of the atrophic area, the stromal fibers run obliquely to the periphery behind the edges of the atrophic area, thus producing a twisting of this border zone of the stroma[Winstanley, 1961 #202]. In severe and prolonged attacks, diffuse iris atrophy occurs. Sometimes a sector of the iris stroma will be disrupted and look like iridoschisis[Romano, 1972 #203]. This may occur with slow progressive atrophy months or years after the acute attack. The pigment epithelium and dilator muscle can be patchily affected and areas may transilluminate. Posterior synechiae may be minimal or extensive. After iridectomy aqueous humor flowing into the anterior chamber can bypass the pupil, favoring formation of postoperative posterior synechiae. Ciliary Body In 1973, Kerman et al.[Kerman, 1973 #645] reported that the ciliary processes may be inserted more anteriorly than normal and extend to the peripheral posterior iris in eyes with angle-closure. With the discovery that plateau iris is caused by large and/or anterior ciliary processes, it is now becoming evident that there is a spectrum of ciliary body size and position. The ciliary body itself does not appear to be adversely affected by acute angle-closure glaucoma. Lens Lens damage can occur as: (1) glaukomflecken, (2) anterior capsular cataract, (3) pigment deposition, posterior synechiae, and fibrosis, (4) cortical cataracts, and (5) nuclear sclerosis. Glaukomflecken ("glaucoma flakes"), or disseminated anterior subcapsular cataracts of acute glaucoma, are the most characteristic signs of lens damage from sudden severe rises of intraocular pressure. They are thought to be caused by pressure necrosis of anterior lens fibers and do not occur at the posterior pole. When intraocular pressure is very high, the lens damage simulates a thin, gray deposit of exudate on the lens surface.[Jones, 1959 #646] With a fall in pressure, the sheet becomes thinner in some places and more condensed in others. Holes develop within it, so it may appear as a coarse, irregular, white net.[Lowe, 1965 #647] Later these flakes become more discrete and appear as small, irregular, blue-white plaques. They tend to follow suture lines of the lens, suggesting necrosis of the tips of the lens fibers. Gradually, the flakes diminish and usually become relatively sparse. As new lens fibers grow from the equator, they overlie the flecks, which sink deeper into the lens and persist as permanent evidence. Glaukomflecken occur almost entirely within the pupil according to its size at the time of the attack.[Sugar, 1946 #648] Glaukomflecken are rare apart from acute angle-closure glaucoma, but have been seen after contusion and chemical burns and also when the anterior chamber has remained flat postoperatively with the cornea and lens in contact for some days. Occasionally, small white plaques resembling glaukomflecken may persist in the anterior surface of the lens. These are anterior capsular cataracts. Anterior cortical lens opacities commonly follow severe attacks of angle-closure glaucoma and may persist as faint irregular streaks that almost invariably progress. The first sign of nuclear sclerosis is a myopic refractive change, which may stabilize or progress. Following severe glaucomatous iritis with extensive posterior synechiae, fibrosis may extend from the iris onto the anterior lens surface. Zonules The zonules can be damaged, so with surgery the lens may move forward with the development of malignant (ciliary block) glaucoma. Occasionally, the opaque lens may slowly dislocate over the years and sink below the pupil. Choroid Kubota et al.[Kubota, 1993 #2833] reported decreased choroidal thickness in 12 eyes with angle-closure glaucoma associated with malignant melanoma of the ciliary body. The decreased thickness was primarily due to decreased choroidal vessel diameter, suggesting decreased choroidal perfusion. Retina and Optic Nerve In intermittent angle-closure glaucoma, even after many attacks, the optic disc is typically unaffected. During the initial states of an acute attack, the disc may appear normal, congested, or edematous with retinal venous congestion and retinal hemorrhages near the disc. When intraocular pressure is acutely elevated in owl monkeys, damage to the nerve fiber layer and ganglion cells precedes damage to most other tissues except the iris.[Anderson, 1975 #200] Douglas et al.[Douglas, 1975 #204] found pallor without cupping following acute attacks, and pallor and cupping in patients with chronic angle-closure. Acutely elevated intraocular pressure in monkeys leads to optic disc congestion lasting several days before pallor and cupping develop.[Zimmerman, 1967 #650] Large retinal hemorrhages near the disc can occur with sudden lowering of intraocular pressure as after hyperosmotic or carbonic anhydrase inhibitor therapy. Retinal function is depressed with raised intraocular pressure.[Uenoyama, 1969 #649] Abnormalities of visual evoked potentials have been reported.[Mitchell, 1989 #1906] In a histological study of 21 eyes with secondary angle-closure glaucoma, Jonas et al.[Jonas, 1992 #1051] found the lamina cribrosa significantly thinner, the optic cup deeper and wider, and the corpora amylacea count lower than in controls. Parapapillary atrophy was significantly greater and occurred more frequently in glaucomatous eyes and the parapapillary retina was significantly thinner.[Jonas, 1992 #1052] A significantly decreased photoreceptor, but not retinal pigment epithelial, cell count was reported in eyes with angle-closure following penetrating trauma.[Panda, 1992 #2786] The final effects will depend on severity and duration of the attack. Recovery may be complete or there may be contraction of isopters and nerve fiber bundle defects.[Douglas, 1975 #204; Lowe, 1973 #624] Pallor without cupping was found to be characteristic of discs after acute angle-closure glaucoma, whereas both pallor and cupping occurred in chronic angle-closure.[Douglas, 1975 #204] In prolonged attacks, when treatment is delayed, glaucomatous damage may progress to the point at which vision is reduced to perception of hand movements or light. In chronic angle-closure glaucoma, the visual field defects and optic disc cupping progress similarly to those of open-angle glaucoma. |
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From: Ray Bonar )
Subject: Angle-closure Glaucoma - Clinical types Date: 1997/12/27 Angle-closure Glaucoma - Clinical types Robert Ritch Ronald F. Lowe The nomenclature for the various clinically distinct types and modes of presentation of angle-closure glaucoma has been inconsistently used by different investigators, by investigators in different countries, and at different points in time. As a result, there is a moderate amount of confusion regarding terminology. This pertains in particular to the terms intermittent, prodromal, and subacute; chronic and creeping; and combined mechanism versus mixed mechanism. Angle-closure glaucoma has long been divided by convention into "primary" and "secondary" forms. Primary angle-closure, or relative pupillary block, is the most common mechanism of angle-closure glaucoma and studies of series of patients with acute angle-closure have been based on this concept. It should be recognized that publications dealing with characteristics of patients with "angle-closure glaucoma" include not only relative pupillary block but other mechanisms as well. However, because relative pupillary block forms the greatest proportion, the data should be regarded as not inordinately skewed. PRESENTATION Angle-closure glaucoma can present with a spectrum of symptomatology, from none at all to severe pain, blurred vision, and nausea. The terminology is based upon the signs and symptoms at the time of diagnosis, and these should not be though of as specific "types" of angle-closure, but merely descriptive phenomena which may vary with time in any individual patient (see Fig. 38-1). For example, a patient with a narrow angle and peripheral anterior synechiae (chronic angle-closure) may have symptoms of intermittent angle-closure attacks which, if not detected or diagnosed, can later present as acute angle-closure glaucoma. The mode of presentation depends on a combination of the percentage of the filtering meshwork occluded by the iris, the rapidity with which the occlusion occurs, and the ease of reversal of the iridotrabecular block. Fourman[Fourman, 1989 #2738] has published a useful flow chart to aid the ophthalmologist in dealing with acute angle-closure glaucoma. Intermittent angle-closure Intermittent angle-closure defines repeated, brief episodes of angle-closure with mild symptoms and elevated intraocular pressure. These resolve spontaneously and ocular function is normal between attacks. Intermittent angle-closure is often a prelude to acute angle-closure. The intraocular pressure is high enough to cause symptoms, but not as high as in a full-blown attack. This may be due to partial angle-closure, which could affect more the narrower superior part of the angle,[Leighton, 1971 #184] or 360° of closure with just enough functioning meshwork remaining above the level of closure to allow some aqueous to escape, or perhaps to a freely reactive pupil, which allows spontaneous reversal of the symptoms once the triggering element is removed. Intermittent attacks are most commonly associated with fatigue, dim light, and using the eyes for near work (see Table 38-1). They tend to recur under similar circumstances and at about the same time of day or evening. The symptoms are a dull ache in or around one eye and mildly blurred vision. Halos around lights are often not seen unless the patient is outdoors. Haloes are believed to result from stretching of the corneal lamellae, causing the cornea to act as a diffraction grating, producing a blue-green central halo and a yellow-red peripheral one. Halos that are seen every night are caused by cataracts, corneal disease, or persistently high intraocular pressure. Transient monocular visual loss has also been noted.[Ravitz, 1984 #185] The patient may recognize the cause and avoid or reduce the activity, such as watching television or reading. The attacks last for about a half hour after cessation of the inciting activity. Sleep is so often recognized as beneficial that many patients go to bed early or take a nap to obtain relief. Amelioration of the attack is attributed to sleep-induced miosis and possibly to decreased intraocular pressure resulting from decreased aqueous humor secretion.[Reiss, 1984 #186] If the symptoms persist overnight, a true attack has developed. Initially, intermittent attacks occur at intervals of weeks or months, but eventually may occur almost nightly. They may continue uneventfully for months or years. Usually only one eye is involved, but bilateral attacks can occur. Because the eyes appear normal between attacks except for a narrow angle, the diagnosis is frequently missed, and even ophthalmologists may be misled by the patient's self-diagnosis of migraine, sinusitis, anxiety or eyestrain. Examination reveals shallow anterior chambers, iris bombé, narrow angles, and sometimes an enlarged or oval pupil. Provocative testing may result in angle-closure, elevated intraocular pressure, and reproduction of the patient's symptoms. The end result of intermittent angle-closure glaucoma usually differs between whites and races with thick, heavily pigmented irides. In whites the attacks are essentially benign and may recur for years without causing damage. Attacks may be accompanied by progressive PAS formation, leading to chronic angle-closure. The greatest danger lies in the possibility of sudden conversion to acute angle-closure glaucoma. Laser iridotomy is definitive if the eye is otherwise normal and the angle not occludable by mechanisms other than pupillary block. In Asians the history may be consistent with intermittent angle-closure glaucoma, but the intraocular pressure is often elevated and the angle variably closed by PAS, depending on the frequency and severity of the attacks. Asian eyes are more prone to "creeping" angle-closure and PAS formation. Iridotomy alone may be insufficient to control intraocular pressure. Blacks also have a greater tendency to develop chronic angle-closure, but it is our impression that the anterior chambers are often deeper than those of Asians and that iris bombé is much less frequent. Both intermittent and acute attacks are less common in blacks than in Asians. Comparative biometric studies would greatly help to increase our understanding of angle-closure in these groups. Subacute angle-closure glaucoma Subacute angle-closure describes a stage in which attacks may be more frequent and prolonged than in intermittent angle-closure, but less so than in acute angle-closure. At least in some cases, this is caused by less than total closure of the angle.[Chandler, 1955 #187] Symptoms of blurred vision, pain, and halos may be more marked than in intermittent angle-closure. Attacks may occur over months or years, finally leading to an acute attack. Subacute attacks are much more common in Asians than in whites and can cause severe damage without much inflammation. They tend to produce a chronically dilated pupil, mild iris atrophy, PAS, and pigment on the iris close to the inferior angle. Intraocular pressure levels and glaucomatous disc and visual field damage vary according to the severity and duration of the attacks. Acute Angle-closure Glaucoma Precipitating events Acute angle-closure glaucoma can lead to irreversible damage. Various stimuli may trigger an attack. Most attacks occur during the evening, beginning mildly and rapidly increasing in severity. Approximately one-third of patients describe episodes of intermittent or subacute angle-closure having occurred before the acute attack. The physiological factors that convert relative pupillary block to absolute pupillary block remain poorly understood, as are those that determine whether an eye will develop acute or chronic angle-closure. Although pupillary block is the common underlying mechanism, the course of the disease depends on the degree and suddenness of the block, the flaccidity and physiologic responses of the iris, and the width and depth of the anterior chamber angle. Absolute pupillary block is most commonly triggered when the pupil is middilated, about 3.5 to 6 mm in diameter.[Chandler, 1952 #105] In this position, the combination of pupillary block and relaxation of the peripheral iris, allowing its forward displacement into the anterior chamber, are maximal. Mapstone[Mapstone, 1968 #127] concluded that the posteriorly directed forces of the dilator and sphincter muscles and the stretching force of the sphincter during contraction are greatest when the pupil is middilated. The most common precipitating events include illness, emotional stress, trauma, intense concentration, and pharmacologic pupillary dilation.[Sugar, 1941 #116; Lowe, 1961 #8957] The role of emotional stress in inducing acute angle-closure should not be underestimated.[Inman, 1929 #190; Egan, 1955 #189; Cross, 1960 #188] A memorable example was a patient who, after narrowly missing being injured by a grenade thrown through his living room window as an expression of some differences of opinion, immediately developed bilateral attacks. Attacks rarely begin simultaneously in both eyes. Minor differences in anterior chamber depth almost invariably result in the eye with the shallower chamber being involved first. A multitude of other inciting factors have been presented in case reports, including acute infectious disorders, acquired immunodeficiency syndrome, tumors, and trauma. In many of these cases, the mechanism either has not been delineated or the block is posterior to the lens, due to uveal effusion. Symptoms and signs The symptoms of an acute attack result from the sudden, marked elevation of intraocular pressure to as high as 80 mmHg. Corneal edema results in blurred vision and intense pain and, secondarily, in lacrimation and lid edema. These, in combination with anxiety and fatigue, lead to nausea and vomiting, whereas vasovagal responses cause bradycardia and diaphoresis. Systemic symptoms may be so severe as to mislead the nonophthalmologist, and some patients have actually undergone unwarranted exploratory laparotomy. We saw one patient whose ataxia, blurred vision, and diagnosis of multiple sclerosis disappeared after laser iridotomy. The diagnosis is usually straightforward (Fig. 38-2). Central visual acuity is reduced and the intraocular pressure is markedly elevated. The lids are swollen and there is conjunctival hyperemia and circumcorneal injection. The cornea is edematous and the pupil usually middilated and vertically oval because of iris sphincter ischemia. The anterior chamber is shallow but usually formed centrally, whereas the midperipheral iris is bowed anteriorly and may touch the cornea peripherally. An inflammatory reaction is present in the anterior chamber. Hypopyon can occur in severe or prolonged attacks.[Zhang, 1984 #8961; Friedman, 1972 #8966] Corneal edema may initially limit gonioscopic and posterior segment examination, even after the topical application of glycerin. Inability to open the angle with indentation gonioscopy at this stage does not mean that the angle will remain sealed after iridotomy, nor does it accurately reflect the presence or extent of PAS. Examination of the opposite eye is particularly useful in differentiating acute angle-closure glaucoma from neovascular, uveitic or phacolytic glaucoma, and usually reveals a shallow anterior chamber and narrow angle. The optic nerve head may be hyperemic and edematous early in the attack. With prolonged attacks or cases in which unrecognized chronic angle-closure glaucoma precedes an acute attack, pallor and cupping, along with visual field damage, may be present. Central retinal vein occlusion may occur as a result of an acute attack[Tornquist, 1958 #195; Sonty, 1981 #2801] or may precipitate one.[Bloome, 1977 #630; Grant, 1973 #631; Hyams, 1972 #632; Mendelsohn, 1985 #633; Weber, 1987 #634; Segal, 1986 #2796] Visual field changes associated with acute pressure elevation usually show nonspecific generalized or upper field constriction.[McNaught, 1974 #191] Early loss of central vision, enlargement of the blind spot, and nerve fiber bundle defects may be found.[Douglas, 1975 #204; Horie, 1975 #635] After normalization of intraocular pressure, the visual fields may also normalize, or patients may be left with reduced color vision, generalized decreased sensitivity, or specific defects. These may be exaggerated by cataract formation or progression. An attack may terminate spontaneously if iris atrophy from tissue necrosis allows aqueous humor to percolate through the iris stroma, equivalent functionally to a spontaneous iridotomy.(Fig. 38-4) However, this occurs more frequently as a result of suppression of aqueous secretion by the high pressure. Spontaneous termination may also be facilitated by a change in the position of the lens-iris contact, or segmental iris constriction with peaking of the pupil.[Phillips, 1963 #192] Chronic Angle-closure Glaucoma Chronic angle-closure refers to an eye in which portions of the anterior chamber angle are permanently closed by PAS. Variable and sometimes conflicting terminology has been used to describe somewhat differently appearing forms. The approach to therapy is similar in all of them. The terminology used in this section is an attempt to differentiate the two pathways by which chronic angle-closure can develop. In the first, iris bombé from relative pupillary block may appositionally close the angle. Prolonged apposition or repeated subacute attacks lead to gradual PAS formation. These usually begin in the superior angle, which is narrower than the inferior angle,[Bhargava, 1973 #142; Mapstone, 1977 #636] as pinpoint synechiae reaching to the midtrabecular meshwork and then gradually expanding in width. In early cases, in which appositional closure is present but PAS have not yet formed, we prefer the term chronic appositional closure. This condition can lead to elevated intraocular pressure and glaucomatous disc and visual field damage without PAS formation.[Foulds, 1957 #637] Eyes with progressive PAS formation may eventually develop an acute attack of angle-closure when pupillary block results in closure of the remaining portions of the angle unaffected by PAS. Many cases, however, develop elevated intraocular pressure and glaucomatous damage in the absence of symptoms. The presentation is similar to that of open-angle glaucoma, with progression of glaucomatous cupping and visual field loss. This is the situation most commonly associated in the United States with chronic angle-closure glaucoma. However, eyes with the same appearance but normal intraocular pressure merely constitute an earlier stage. PAS may also form during an acute attack, remaining after iridotomy has opened the unaffected portions of the angle. These PAS are usually high and broad. When first observed at this stage, it is impossible to determine whether the PAS formed before or during the attack, or at both times. In eyes with darker irides, a second mechanism of progressive angle-closure is more common. The closure is circumferential and begins in the deepest portion of the angle. Closure occurs more evenly in all quadrants, so that the angle progressively becomes more shallow. The appearance over time is of a progressively more anterior iris insertion. Lowe[Lowe, 1964 #194] has termed this creeping angle-closure. The PAS gradually creep up the ciliary face to the scleral spur and then to the trabecular meshwork. Insertion of the iris at or anterior to the scleral spur is rare in young individuals, and in many eyes with angle-closure glaucoma that have such an insertion, creeping angle-closure is the underlying reason. Creeping angle-closure is uncommon in whites but much more prevalent in Asians, in whom it ranks high as a cause of blindness. Black patients with angle-closure also tend to have this form. It occurs in eyes with slightly deeper, though still shallow, anterior chambers than are found in acute angle-closure. The gradual shortening of the angle in the presence of iris bombé brings the peripheral iris close to the external angle wall more and more anteriorly, narrowing the gap between the iris and the trabecular meshwork. Eventually, an acute attack may supervene (more commonly in Asians), or the PAS may permanently occlude the trabecular meshwork and lead to elevated intraocular pressure and glaucomatous damage (more commonly in black patients). The intraocular pressure in eyes with chronic angle-closure may be normal or elevated. As PAS formation progresses in the absence of intermittent attacks, the pressure rises gradually as less and less functional trabecular meshwork becomes available. In eyes with intermittent attacks, the pressure rises more rapidly relative to the extent of PAS formation caused by recurrent damage to the trabecular meshwork by the transient angle-closure. Dispersed pigment granules collect in the iridocorneal angle where the peripheral iris is in contact with the cornea. Dense blotches of pigment on the meshwork, particularly in the superior angle, or deposits of black pigment in the angle of a lightly pigmented iris, are highly suggestive of previous appositional closure. If the angle opens, this deposited line of pigment shows the extent of previous angle closure and can sometimes be a helpful diagnostic feature. The anterior chamber is quiet and usually deeper than in eyes with acute angle-closure glaucoma. The pupil is normal. The gradual elevation of intraocular pressure does not result in corneal endothelial decompensation, and edema is rare. The intraocular pressure is usually less than 40 mmHg and does not reach the levels found in acute angle-closure glaucoma. Symptoms are absent until the pressure rises high enough to affect the cornea or until extensive visual field damage has occurred. Although iridotomy will eliminate the pupillary block, intraocular pressure often remains elevated, and further medical treatment or surgery is required. Absolute Glaucoma Absolute glaucoma refers to an eye with no light perception and a persistently elevated intraocular pressure. The angle initially may be open or closed, but in phakic eyes an intumescent cataract often develops and leads to an associated angle-closure. The time required for a neglected angle-closure attack to cause total blindness is variable and depends on the severity of the acute attack, but appears to be an average of 1 to 2 years. Treatment is palliative and intraocular surgery is unwarranted. If corneal edema and pain are not relieved by topical beta-adrenergic blocking agents, steroids, and cycloplegics, noninvasive cycloablation may be performed. If this is insufficient or if complications such as phacolytic glaucoma develop, evisceration or enucleation may be necessary. Phthisis bulbi is not an uncommon outcome. PLATEAU IRIS Plateau iris configuration refers to the anatomic structure in which the iris root angulates forward and then centrally.[Tornquist, 1958 #195] In many cases, the iris root is short and is inserted anteriorly on the ciliary face, so that the angle is shallow and narrow, with a sharp drop-off of the peripheral iris at the inner aspect of the angle. The iris surface appears flat and the anterior chamber is not unusually shallow on slit-lamp examination. Plateau iris syndrome refers to the development of angle-closure, either spontaneously or after pupillary dilation, in an eye with plateau iris configuration despite the presence of a patent iridectomy or iridotomy. Some patients may develop acute angle-closure glaucoma[Godel, 1968 #196; Lowe, 1968 #197; Lowe, 1981 #198; Wand, 1977 #199] The risk of postoperative pupillary dilation after iridectomy or iridotomy is infrequently realized. Until recently, plateau iris syndrome was considered a rare entity. We have differentiated two subtypes.[Lowe, 1989 #2841] In the complete syndrome, which comprises the classic situation and is rare, intraocular pressure rises when the angle closes with pupillary dilation. In the incomplete syndrome, intraocular pressure does not change. The important factor differentiating the complete and incomplete syndromes is the level of the iris stroma with respect to the angle structures, or the "height" to which the plateau rises . If the angle closes to the upper trabecular meshwork or Schwalbe's line, intraocular pressure rises, whereas if the angle closes partially, leaving the upper portion of the filtering meshwork open, the pressure will not rise. This is a far more common situation and is clinically significant as these patients can develop PAS up to years after a successful iridotomy produces what appears as a well-opened angle. Plateau iris results from large and/or anteriorly positioned ciliary processes holding up the peripheral iris and maintaining its apposition to the trabecular meshwork ..[Pavlin, 1992 #240; Ritch, 1992 #1046; Wand, 1993 #3212] When indentation gonioscopy is performed in such an eye, the ciliary processes prevent posterior movement of the peripheral iris. As a result, a sinuous configuration results (sine wave sign), in which the iris follows the curvature of the lens, reaches its deepest point at the lens equator, then rises again over the ciliary processes before dropping peripherally. Much more force is needed during gonioscopy to open the angle than in pupillary block because the ciliary processes must be displaced, and the angle does not open as widely. In a morphometric study of the ciliary sulcus, Orgül et al.[Orgül, 1993 #2835] proposed that the displacement of the pars plicata from the peripheral iris to the iris root during embryogenesis may be incomplete in eyes of shorter axial length. Darkroom gonioscopy is important in plateau iris as well as in pupillary block, and an angle which appears open in the light can close in the dark. Patients with plateau iris tend to be female, younger (30s to 50s) and less hyperopic than those with relative pupillary block, and often have a family history of angle-closure glaucoma. Except in the rare younger patients (20s and 30s), some element of pupillary block is also present. However, because of the nature of the anatomic relationships of the structures surrounding the posterior chamber, the degree of relative pupillary block necessary to induce angle-closure is less than that in primary angle-closure glaucoma; this seems to account for the deeper anterior chamber and flatter iris surface in eyes with angle-closure and plateau iris. Patients with plateau iris who develop angle-closure glaucoma are also somewhat younger than those with pupillary block angle-closure glaucoma. As a general rule, the older the patient, the less prominent the angulation of the peripheral iris and the greater the element of pupillary block. Iridotomy is successful at opening the angle when a component of pupillary block is present, but periodic gonioscopy remains indicated, as the angle can narrow further with age due to enlargement of the lens. If plateau iris was not diagnosed before iridotomy and intraocular pressure is elevated postlaser, careful gonioscopy should be performed. If the angle is open, secondary damage to the trabecular meshwork or pigment liberation with dilation are the most likely causes. If the angle is closed, the differential diagnosis, besides plateau iris, should include malignant glaucoma, in which the anterior chamber is extremely shallow; PAS, which can be ruled out by indentation gonioscopy; or incomplete iridectomy. Although plateau iris syndrome is usually recognized in the postoperative period, it may develop years later. Patients with plateau iris configuration should not be assumed to be permanently cured, even though plateau iris syndrome does not develop immediately. IRIDOSCHISIS Iridoschisis is a separation of the anterior and posterior iris stromal layers which occurs primarily in older women. It is usually bilateral, but may be asymmetric. The amount of stromal separation can sometimes be dramatic. Iridoschisis has been associated in the literature with narrow angles and angle-closure glaucoma.[Romano, 1972 #203; Salmon, 1992 #8638; Loewenstein, 1948 #8969; Loewenstein, 1945 #8968; Haik, 1952 #8970; McCulloch, 1950 #8971; Mills, 1967 #8972; Rodrigues, 1983 #8973; Carter, 1953 #8974] Whether angle-closure requires an eye with a preexisting narrow angle is unknown. ANGLE-CLOSURE GLAUCOMAS ASSOCIATED WITH DRUGS AND OTHER DISORDERS Miotic-induced Angle-closure Glaucoma Prolonged miotic treatment in eyes with open-angle glaucoma and narrow angles may lead to pupillary block and angle-closure glaucoma. We have seen chronic angle-closure develop after several years of miotic therapy in eyes that initially had wide open angles. In some eyes, zonular relaxation occurs more readily than in others, so that anterior lens movement and an increase in axial lens thickness may facilitate pupillary block and angle-closure. In other eyes, there is little change in the lens, but progressively increasing pressure in the posterior chamber gradually pushes the peripheral iris against the trabecular meshwork. It is our impression that eyes with exfoliation syndrome are particularly prone to develop miotic-induced angle-closure. In these eyes, the iris is thicker and stiffer than normal due to deposition of exfoliation material within the stroma. In addition, zonular weakness allows the lens to move forward, leading to pupillary block. Less commonly, miotic therapy can have a pronounced effect on lens position and trigger malignant glaucoma.[Gorin, 1966 #625; Levene, 1972 #638; Merritt, 1977 #639; Rieser, 1972 #626] Unequal anterior chamber depths, a progressive increase in myopia, or progressive shallowing of the anterior chamber are clues to the correct diagnosis. Combined Mechanism Glaucoma Combined mechanism glaucoma refers to situations in which both open-angle and angle-closure components are present. A patient may have open-angle glaucoma and either narrow angles with superimposed intermittent angle-closure glaucoma or miotic-induced angle-closure. The most common situation is that in which angle-closure, either acute or chronic, is eliminated by iridotomy and/or iridoplasty and intraocular pressure still remains elevated, with or without the presence of PAS of any extent. Another situation occurs in eyes with exfoliation syndrome successfully treated for angle-closure glaucoma, in which open-angle glaucoma can develop independently years later with progressive blockage of the trabecular meshwork. In all of these cases, the residual open-angle component is treated as open-angle glaucoma. Mixed Mechanism Glaucoma This term is often used interchangeably with combined mechanism glaucoma, creating additional confusion. It is better to reserve this term to describe residual appositional angle-closure by another mechanism (plateau iris, phacomorphic, ciliary block) remaining after elimination of pupillary block with partial opening of the angle. Phacomorphic Glaucoma Swelling of the lens may convert an anterior chamber of medium depth into one that is markedly shallow and precipitate acute angle-closure glaucoma. In countries in which cataracts are prevalent and operations not readily available, acute angle-closure glaucoma from swollen hypermature lenses is common. Again, some element of pupillary block may also be present. Phacomorphic glaucoma is often unresponsive to medical therapy, and paradoxical reactions to pilocarpine are common. Pilocarpine, even in elderly patients, increases axial lens thickness and causes anterior lens movement, further shallowing the anterior chamber.[Abramson, 1973 #89] Slight lens subluxation in eyes of elderly patients, formerly termed senile subluxation of the lens, is most commonly associated with exfoliation syndrome. Mild iridodonesis may be seen. In some cases, anterior lens movement may be sufficient to cause angle-closure glaucoma, usually chronic. These eyes are more susceptible to the development of miotic-induced angle-closure during treatment for open-angle glaucoma. Iridotomy usually suffices to eliminate pupillary block and the angle-closure component. In younger patients anterior lens movement is often associated with secondary causes or ciliary block. After iridotomy, iridoplasty may be necessary to eliminate continued appositional closure if cycloplegics are unsuccessful at maintaining a more posterior lens position and an open angle. This topic is discussed more fully in Chapter 58. Malignant Glaucoma Malignant (ciliary block) glaucoma[Levene, 1972 #638; Shaffer, 1978 #640; Simmons, 1972 #641; Weiss, 1972 #642; Dueker, 1994 #4726] is a multifactorial disease in which the following components may play varying roles: (1) previous acute or chronic angle-closure glaucoma, (2) shallowness of the anterior chamber, (3) forward movement of the lens, (4) pupillary block by the lens or vitreous, (5) slackness of the zonules, (6) anterior rotation and/or swelling of the ciliary body, (7) thickening of the anterior hyaloid membrane, (8) expansion of the vitreous, and (9) posterior aqueous displacement into or behind the vitreous. This topic is covered in Chapter 39. Swelling or anterior rotation of the ciliary body with forward rotation of the lens-iris diaphragm and relaxation of the zonular apparatus causes anterior lens displacement which in turn causes direct angle-closure by physically pushing the iris agains the trabecular meshwork.[Phelps, 1974 #643] Accurate diagnosis and treatment are often more difficult when the initiating event is posterior to the lens-iris diaphragm. In predisposed eyes, miotic therapy can have a pronounced effect on lens position and trigger malignant glaucoma.[Gorin, 1966 #625; Levene, 1972 #638; Merritt, 1977 #639; Rieser, 1972 #626] Unequal anterior chamber depths, a progressive increase in myopia, or progressive shallowing of the anterior chamber are clues to the correct diagnosis. Malignant glaucoma may occur following cataract surgery with posterior chamber intraocular lens implantation.[Brown, 1986 #1255; Epstein, 1984 #1395; Lynch, 1986 #2773; Duy, 1987 #2729; Reed, 1990 #1054; Vajpayee, 1991 #2812; Tello, 1993 #1963] The differential diagnosis includes pupillary block, choroidal hemorrhage, and ciliochoroidal effusion with anterior rotation of the ciliary body and secondary angle closure. Shallowing of the central anterior chamber occurs in pseudophakic malignant glaucoma, but not in pupillary block. Rupture of the anterior hyaloid face is usually curative and allows aqueous to move into the anterior segment. We have examined several patients with presumed aqueous misdirection in whom an annular ciliary body detachment had caused anterior movement of the ciliary body. Whether a posterior diversion of aqueous flow is present in these disorders is unknown. Some of the disorders that can lead to this picture are covered in other chapters. These include drug sensitivity (e.g., sulfonamides, see Chapter 56); angle-closure after panretinal photocoagulation, central retinal vein occlusion, or scleral buckling procedures (see Chapters 50 and 51); uveal effusion from posterior segment inflammation; ciliary body swelling, inflammation, or cysts ; posterior segment tumors (see Chapter 52). Aphakic and pseudophakic malignant glaucoma are discussed in Chapter 61. Retinopathy of prematurity Angle-closure may occur in very young children with retinopathy of prematurity due to forward shifting of the lens-iris diaphragm (see also Chapter 44).[Cohen, 1964 #8926; Hittner, 1979 #1894; Pollard, 1980 #5292; McCormick, 1971 #1898; Laws, 1994 #8928; Kushner, 1982 #1057] These children do not respond to iridotomy. In young adults with this condition, there appears to be a superimposed element of pupillary block, and iridotomy may be successful.[Ueda, 1988 #8927; Smith, 1984 #1899] Nanophthalmos Nanophthalmos is a bilateral, often familial form of microphthalmos unaccompanied by other congenital malformations. It is characterized by hyperopia, small corneal diameter, thick sclera, and narrow angles.[O'Grady, 1971 #8231] Angle-closure glaucoma usually appears between the ages of 20 and 50 years. Although by definition, nanophthalmos refers to an eye of axial length less than 20 mm, there is obviously a gradient of hyperopic refraction, the degree of hyperopia correlating inversely with axial length. There is an inverse correlation between the degree of hyperopia and the age of onset of angle-closure. The youngest reported patient was 9 years old with 21 diopters of hyperopia.[Hatcher, 1952 #8962] However, acute angle-closure glaucoma can also develop in the elderly.[Cross, 1976 #8964] The sclera in nanophthalmic eyes is abnormally thick.[Brockhurst, 1975 #2710] Electron microscopy reveals disordered collagen bundles and fraying of collagen fibrils, with absence of elastic fibers.[Trelstad, 1982 #5595; Stewart, 1991 #2804] In tissue culture, scleral fibroblasts of eyes with nanophthalmos appear to have an abnormal glycosamine metabolism, which might explain the abnormal packing of collagen bundles and scleral thickening.[Shiono, 1992 #2798] Uveal effusion is common, either spontaneously or after surgical procedures, including filtration surgery or cataract extraction.[Brockhurst, 1975 #2710; Ryan, 1982 #8963] Associations with retinitis pigmentosa[Ghose, 1985 #8230; MacKay, 1987 #1042] and Hallerman-Streiff syndrome[Stewart, 1991 #2804] have been reported. Laser iridotomy for angle-closure is usually unsuccessful or only temporarily successful. If successful initially, lens enlargement with age can lead to appositional closure. Iridoplasty (gonioplasty) to flatten the peripheral iris was first reported in 1979 by Kimbrough et al.[Kimbrough, 1979 #1412] Combined iridotomy and iridoplasty often brings the angle-closure under control.[Jin, 1990 #2759] Uveal effusions have been reported after both laser iridotomy[Karjalainen, 1986 #1408] and trabeculoplasty.[Good, 1988 #2742] The risks of surgical intervention include malignant glaucoma, expulsive suprachoroidal hemorrhage, and retinal detachment.[Hyams, 1990 #8965] Posterior sclerotomy may or may not be successful at preventing uveal effusion.[Calhoun, 1975 #8047; Jin, 1990 #2759] Vortex vein decompression for nanophthalmic uveal effusion was described by Brockhurst,[Brockhurst, 1980 #5305] but the technique is technically difficult. Partial thickness sclerectomies and sclerostomies were reported in one patient to achieve complete resolution of retinal and choroidal detachments, suggesting impairment of transscleral protein transport as a primary pathophysiologic mechanism in nanophthalmic uveal effusion.[Allen, 1988 #1921] Subsequently, Wax et al. described success with anterior lamellar sclerectomy without sclerostomy.[Wax, 1992 #2820] CLINICAL PATHOLOGY OF ANGLE-CLOSURE GLAUCOMA When the angle totally occludes, aqueous outflow is blocked, and intraocular pressure rises markedly. The effect of the elevated pressure depends on the magnitude and rapidity of its rise. At the same time the pupillary reaction to direct light decreases. The pupil becomes partly dilated and tends to assume a vertically oval shape, but may be oblique or even horizontal. Cornea With very high intraocular pressure, corneal edema is severe. Transient loss of sensitivity can occur.[Patel, 1988 #2787] The cornea is cloudy and may be twice its usual thickness. Endothelial cell density is reduced by as much as 33% following an acute attack and is greater the longer the duration of the attack.[Bigar, 1982 #644; Mapstone, 1985 #121; Markowitz, 1984 #652; Brooks, 1991 #8958; Olsen, 1980 #3558; Malaise-Stals, 1984 #8959] Corneal decompensation may occur in eyes with preexisting endothelial compromise.[Krontz, 1988 #1932; Hyams, 1983 #8960] When the pressure is lowered, the edema clears first at the periphery. Folds in Descemet's membrane form. Following prolonged high pressure, corneal edema and striate keratopathy may persist for some days. With severe damage, chronic edema may persist, lipid is deposited, and the cornea may become fibrosed and vascularized. Iris Partial necrosis of the iris stroma is the first sign of damage from elevated intraocular pressure experimentally.[Anderson, 1975 #200] At pressures over 60 mmHg, the pupil becomes increasingly resistant to miotics, probably caused by direct pressure on the sphincter muscle.[Charles, 1970 #201] The sphincter may respond to miotics after the pressure has been lowered, but when intraocular pressure exceeds the diastolic blood pressure, the iris around the pupil becomes ischemic.[Charles, 1970 #201] The sphincter muscle then loses its ability to contract even if intraocular pressure is lowered, and patchy atrophy of the iris occurs. The dilator muscle is less affected than the sphincter, so that the instillation of 10% phenylephrine usually causes increased pupillary dilation. In the segments in which the stroma is not obviously atrophic, the pupillary margin is thick, rolled, and bunched with radial folds. At the margins of the atrophic area, the stromal fibers run obliquely to the periphery behind the edges of the atrophic area, thus producing a twisting of this border zone of the stroma[Winstanley, 1961 #202]. In severe and prolonged attacks, diffuse iris atrophy occurs. Sometimes a sector of the iris stroma will be disrupted and look like iridoschisis[Romano, 1972 #203]. This may occur with slow progressive atrophy months or years after the acute attack. The pigment epithelium and dilator muscle can be patchily affected and areas may transilluminate. Posterior synechiae may be minimal or extensive. After iridectomy aqueous humor flowing into the anterior chamber can bypass the pupil, favoring formation of postoperative posterior synechiae. Ciliary Body In 1973, Kerman et al.[Kerman, 1973 #645] reported that the ciliary processes may be inserted more anteriorly than normal and extend to the peripheral posterior iris in eyes with angle-closure. With the discovery that plateau iris is caused by large and/or anterior ciliary processes, it is now becoming evident that there is a spectrum of ciliary body size and position. The ciliary body itself does not appear to be adversely affected by acute angle-closure glaucoma. Lens Lens damage can occur as: (1) glaukomflecken, (2) anterior capsular cataract, (3) pigment deposition, posterior synechiae, and fibrosis, (4) cortical cataracts, and (5) nuclear sclerosis. Glaukomflecken ("glaucoma flakes"), or disseminated anterior subcapsular cataracts of acute glaucoma, are the most characteristic signs of lens damage from sudden severe rises of intraocular pressure. They are thought to be caused by pressure necrosis of anterior lens fibers and do not occur at the posterior pole. When intraocular pressure is very high, the lens damage simulates a thin, gray deposit of exudate on the lens surface.[Jones, 1959 #646] With a fall in pressure, the sheet becomes thinner in some places and more condensed in others. Holes develop within it, so it may appear as a coarse, irregular, white net.[Lowe, 1965 #647] Later these flakes become more discrete and appear as small, irregular, blue-white plaques. They tend to follow suture lines of the lens, suggesting necrosis of the tips of the lens fibers. Gradually, the flakes diminish and usually become relatively sparse. As new lens fibers grow from the equator, they overlie the flecks, which sink deeper into the lens and persist as permanent evidence. Glaukomflecken occur almost entirely within the pupil according to its size at the time of the attack.[Sugar, 1946 #648] Glaukomflecken are rare apart from acute angle-closure glaucoma, but have been seen after contusion and chemical burns and also when the anterior chamber has remained flat postoperatively with the cornea and lens in contact for some days. Occasionally, small white plaques resembling glaukomflecken may persist in the anterior surface of the lens. These are anterior capsular cataracts. Anterior cortical lens opacities commonly follow severe attacks of angle-closure glaucoma and may persist as faint irregular streaks that almost invariably progress. The first sign of nuclear sclerosis is a myopic refractive change, which may stabilize or progress. Following severe glaucomatous iritis with extensive posterior synechiae, fibrosis may extend from the iris onto the anterior lens surface. Zonules The zonules can be damaged, so with surgery the lens may move forward with the development of malignant (ciliary block) glaucoma. Occasionally, the opaque lens may slowly dislocate over the years and sink below the pupil. Choroid Kubota et al.[Kubota, 1993 #2833] reported decreased choroidal thickness in 12 eyes with angle-closure glaucoma associated with malignant melanoma of the ciliary body. The decreased thickness was primarily due to decreased choroidal vessel diameter, suggesting decreased choroidal perfusion. Retina and Optic Nerve In intermittent angle-closure glaucoma, even after many attacks, the optic disc is typically unaffected. During the initial states of an acute attack, the disc may appear normal, congested, or edematous with retinal venous congestion and retinal hemorrhages near the disc. When intraocular pressure is acutely elevated in owl monkeys, damage to the nerve fiber layer and ganglion cells precedes damage to most other tissues except the iris.[Anderson, 1975 #200] Douglas et al.[Douglas, 1975 #204] found pallor without cupping following acute attacks, and pallor and cupping in patients with chronic angle-closure. Acutely elevated intraocular pressure in monkeys leads to optic disc congestion lasting several days before pallor and cupping develop.[Zimmerman, 1967 #650] Large retinal hemorrhages near the disc can occur with sudden lowering of intraocular pressure as after hyperosmotic or carbonic anhydrase inhibitor therapy. Retinal function is depressed with raised intraocular pressure.[Uenoyama, 1969 #649] Abnormalities of visual evoked potentials have been reported.[Mitchell, 1989 #1906] In a histological study of 21 eyes with secondary angle-closure glaucoma, Jonas et al.[Jonas, 1992 #1051] found the lamina cribrosa significantly thinner, the optic cup deeper and wider, and the corpora amylacea count lower than in controls. Parapapillary atrophy was significantly greater and occurred more frequently in glaucomatous eyes and the parapapillary retina was significantly thinner.[Jonas, 1992 #1052] A significantly decreased photoreceptor, but not retinal pigment epithelial, cell count was reported in eyes with angle-closure following penetrating trauma.[Panda, 1992 #2786] The final effects will depend on severity and duration of the attack. Recovery may be complete or there may be contraction of isopters and nerve fiber bundle defects.[Douglas, 1975 #204; Lowe, 1973 #624] Pallor without cupping was found to be characteristic of discs after acute angle-closure glaucoma, whereas both pallor and cupping occurred in chronic angle-closure.[Douglas, 1975 #204] In prolonged attacks, when treatment is delayed, glaucomatous damage may progress to the point at which vision is reduced to perception of hand movements or light. In chronic angle-closure glaucoma, the visual field defects and optic disc cupping progress similarly to those of open-angle glaucoma. |
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