Inflammation in the anterior segment

Inflammation of the anterior segment producing ring posterior synechiae to the lens implant or vitreous face, and occluding the pupillary aperture is an important cause of secondary angle-closure glaucoma with pupil block. Pupil block may develop insidiously in low-grade iritis with gradual seclusion of the pupil or suddenly in acute iritis. Treatment is aimed at preventing seclusion of the pupil with topical steroids and mydriatics but for the established condition laser or surgical iridectomy is necessary to break the block. Before the advent of YAG laser iridotomy peripheral iridectomy was performed routinely during most intraocular surgical procedures to avoid potential pupil block from postoperative inflammation.

Fig. 8.1 In this patient with uveitis pupil block due to seclusion of the pupil is evident from the forward convexity of the iris resulting in a shallow peripheral anterior chamber, whereas the central chamber remains deep. The deep central anterior chamber distinguishes pupil block from malignant glaucoma with forward movement of the iris–lens diaphragm secondary to posterior segment pathology or pupil block from intumescent cataract.

Fig. 8.2 These two slit-image photographs show the same patient (left) before and (right) after treatment. Pupil block and iris bombè are present. A deepening of the peripheral part of the anterior chamber is clearly evident following laser iridotomy (right).

Pupil block in pseudophakic and aphakic eyes

Modern techniques of phacoemulsification cataract surgery with posterior chamber lens implantation are sufficiently free from postoperative inflammation not to require an iridotomy and pupil block is rarely seen in these eyes. When pupil block does occur it may be due to pupil capture of the implant or from occlusion of the pupil by posterior synechiae to the implant or lens capsule remnants. Intracapsular cataract surgery used to cause pupil block as an acute event although sometimes this did not become apparent until weeks later. Similar findings may be seen with aphakia when posterior synechiae can form between the iris and anterior hyaloid face. Pupil block is suggested by a combination of raised IOP and peripheral shallowing of the anterior chamber. Although extensive prolapse of gel through the pupil sometimes occurs there is usually little vitreous prolapse and the central anterior chamber is of normal depth with peripheral shallowing.

The established condition is treated by laser iridotomy and, when successful, there is immediate deepening of the peripheral anterior chamber. Laser iridotomies, however, are small and may become occluded with fibrin or vitreous gel. A surgical iridectomy can therefore be required or, sometimes, a vitrectomy is necessary performed to re-establish aqueous flow. Eyes containing silicone oil should have a surgical iridectomy performed inferiorly as the oil floats up to occlude a superior iridotomy. Pseudophakic pupil block can occur in eyes with an anterior chamber lens without iridectomy or if an iridotomy is nonfunctioning from blockage by vitreous or capsular remnants. A rigid anterior chamber lens may maintain axial anterior chamber depth with iris ballooning around the edges of the lens making the periphery of the anterior chamber more shallow and occluding the angle.

Fig. 8.3 In this patient there is pupil block from posterior synechiae to the vitreous face in an aphakic eye. The slit-lamp image shows peripheral shallowing of the anterior chamber. The extent to which the gel prolapses into the anterior chamber determines the central depth.

Fig. 8.4 Anterior chamber intraocular lens implantation without peripheral iridectomy is likely to cause pupil block. In this case the iris can be seen bulging forwards around the implant. Although the angle can often be reopened by a laser iridotomy this readily reoccludes with vitreous and so does not reliably prevent recurrence. Surgical iridectomy is definitive but difficult to achieve through a corneal phacoemulsification wound unless it is placed temporally. Temporal iridectomies may cause glare or monocular diplopia, however, and so surgical entry by a separate superior corneal incision is preferable.

Fig. 8.5 Silicone oil floats on aqueous humour. Eyes with posterior segment silicone oil retinal tamponade require an inferior iridectomy to prevent pupil block.

Forward movement of the anterior lens surface

Intumescence of the lens, anterior dislocation or age-related growth changes in the lens can all produce pupil block and angle closure by forward movement of the anterior lens surface. These eyes require lens removal or iridotomy. Angle closure may still occur after iridotomy as a result of progressive increase in antero-posterior depth of the lens.

Fig. 8.6 Acute angle closure due to an intumescent cataractous lens. The eye is red with a hazy view of the anterior segment from corneal oedema, with a fixed irregular semidilated pupil from iris infarction. The slit image shows the corneal oedema and a very shallow anterior chamber. Some uveitis may be present because of ischaemia, and this must be differentiated from the larger accumulations of lens material and macrophages seen with phacolytic glaucoma (see Fig. 8.49).

Fig. 8.7 Slit-image photography of the left and right eye of this patient demonstrates a subluxed lens in the left eye. The anterior chamber is shallow and further examination shows that the anterior lens surface is closer to the posterior corneal surface inferiorly than superiorly occluding the pupil and producing pupillary block.

Fig. 8.8 Occasionally pupillary dilatation allows a subluxed lens to swing into the pupillary plane and block communication between the posterior and anterior chamber. Careful positioning of the patient and the use of miotics usually allow the lens to be repositioned safely until definitive treatment can be arranged which in this case is removal of the lens.

Fig. 8.9 Pupil-block glaucoma following traumatic anterior dislocation of the cataractous lens. The slit-image view demonstrates how the pupil is completely blocked by the lens with the peripheral iris bowed anteriorly around the lens. Prolonged lens-cornea contact may result in endothelial damage.

Angle closure from changes in the posterior segment

Tumours form the most important (although the least common) group of conditions in the posterior segment that push the lens–iris diaphragm forwards. Other conditions that may cause an increase in the volume of the posterior segment include choroidal effusions arising either spontaneously or secondary to intraocular surgery, posterior scleritis, encircling bands used in retinal detachment surgery and rarely even ciliary body cysts. An increase in permeability following a breakdown of the blood–retinal barrier may occur after panretinal photocoagulation or central retinal vein occlusion and lead to either a choroidal effusion or a volume increase of the posterior segment pushing the lens–iris diaphragm forwards.

Fig. 8.10 A patient with a long-standing blind eye presented with recent onset of pain, conjunctival oedema and anterior chamber haemorrhage. Posterior segment ultrasonographic examination showed a large choroidal melanoma. Hemisection of the enucleated eye demonstrates a large haemorrhagic choroidal melanoma together with an anteriorly displaced lens and loss of the anterior chamber.

Fig. 8.11 Posterior scleritis may be associated with an annular choroidal effusion that causes the ciliary body to rotate forward about the scleral spur and the iris–lens diaphragm to move forward to produce angle-closure glaucoma. Ciliary body detachment may result in a normal or low IOP, even in the presence of angle closure. This photograph shows a red eye with diffuse anterior and posterior scleritis, although many of these eyes are completely white with inflammation limited to the posterior sclera alone.

Fig. 8.12 A fundus painting of the same patient reveals an annular choroidal effusion (see also Ch. 5).

Fig. 8.13 In less obvious cases than the case illustrated, such effusions are easily missed unless the peripheral fundus is inspected carefully under full mydriasis. B-scan ultrasonography is very useful.

By courtesy of Ms M Restori.

Fig. 8.14 Persistent hyperplastic primary vitreous can produce a contracting fibrotic retrolental mass with forward rotation of the ciliary body and lens–iris diaphragm pushing the iris forwards to occlude the angle. The anterior chamber is often shallow in these eyes making angle occlusion more likely. (Top left) This slit-image photograph shows a shallow anterior chamber and retrolental mass. (Top right) Following mydriasis elongated ciliary processes can be seen being pulled into the mass. (Bottom right) Gonioscopy demonstrates traction and elongation of the ciliary processes.

Malignant glaucoma (ciliolenticular block or aqueous misdirection syndrome)

The term ‘malignant glaucoma’ was originally used to describe this syndrome because the eye did not respond to, and appeared to be made worse by, treatment with pilocarpine. It is used to describe eyes with a very high IOP, absent or shallow anterior chambers and a retrolenticular accumulation of aqueous humour in the absence of pupil block. The most common cause of this uncommon condition is drainage surgery on an eye with a shallow anterior chamber although other forms of intraocular surgery that decompress the anterior chamber can also cause it. Surgery on the fellow eye may be followed by the same result.

The mechanism appears to be an obstruction to forward flow of aqueous humour in the presence of a shallow anterior chamber causing misdirection of aqueous into the posterior segment with pooling in the vitreous gel. Aqueous misdirection appears to occur because of a change in the anatomical relationship between the peripheral vitreous and ciliary processes with the latter rotating forward when the eye is decompressed so that aqueous flows posteriorly. This causes the lens–iris diaphragm to move forward to occlude the angle with central shallowing of the anterior chamber.

The treatment for malignant glaucoma should initially be topical atropine (to relax the ciliary muscle and pull the lens–iris diaphragm posteriorly) together with acetazolamide, beta-blockers and hyperosmotic agents (to lower IOP, dehydrate the vitreous and reduce its volume). Pilocarpine makes the situation worse. Surgical treatment involves decompression of the retrolenticular aqueous pool by pars plana vitrectomy combined with perforation of the anterior hyaloid face and removal of the lens.

For pseudophakic malignant glaucoma the treatment of first choice is YAG laser anterior vitreolysis and posterior capsulotomy. This photodisruption may allow aqueous to percolate from the loculated pools within the anterior vitreous into the posterior chamber and thus relieves the block to aqueous flow. However pars plana vitrectomy is often required as laser vitreolysis may only provide a temporary solution. A process similar to that described above can occur in eyes that are aphakic. Ciliovitreal block can occur if adhesions exist between the anterior hyaloid face and the iris; this may be difficult to distinguish from aphakic pupil block. The diagnosis is confirmed, however, if following YAG laser iridotomy the condition is not resolved and vitreous is seen to be occluding the iridotomy. Surgical or YAG laser rupture of the anterior hyaloid face is curative in this condition.

Fig. 8.15 This diagram illustrates how aqueous passes posteriorly and then pushes the lens–iris diaphragm forwards.

Fig. 8.16 These two slit-lamp photographs of the anterior segments of each eye of a patient demonstrate a shallow anterior chamber in the right eye (left), whereas the left eye (right) has virtually no anterior chamber. The left eye had recently undergone a trabeculectomy followed by loss of the anterior chamber from malignant glaucoma. It is worth using topical atropine in higher-risk eyes at the end of filtration surgery to prevent this.

Synechial closure of the angle

The uveitic eye can develop PAS even if its angle is not narrow. In severe anterior uveitis the angle may become bridged by fibrin which draws the peripheral iris towards the trabecular meshwork.

PAS may also occur when the anterior chamber is shallow enough to allow iris contact with the angle structures. Examples are hypotony from a leaking wound, corneal perforation or cyclodialysis cleft and chronic or intermittent apposition from uncorrected pupil block; these are hastened by coincidental inflammation.

Fig. 8.17 PAS (left) should be distinguished from fine strands from the anterior iris surface to the trabecular meshwork which may be seen in normal eyes (right).

Fig. 8.18 Slit-image and gonioscopic photographs demonstrate the development of PAS in chronic uveitis. Although often confined to the inferior angle such synechiae can extend circumferentially. With sarcoidosis, trabecular granulomas occasionally form as focal lesions around the circumference of the angle and, if untreated, may produce small areas of PAS (see Ch 10).

Fig. 8.19 In this eye the pupil is occluded by posterior synechiae. Chronic gross circumferential PAS occlude the angle probably as a result of previous pupil block.

Small eyes

There are a number of ocular conditions in which the eye itself is considerably smaller than normal (e.g. congenital high hyperopia, nanophthalmos, mucopolysaccharidoses, congenital syphilis). Glaucoma occurs frequently in these rare conditions from crowding of the angle by the iris. Surgical iridectomy in such patients who often have very shallow anterior chambers preoperatively may actually precipitate malignant glaucoma and is therefore contraindicated, as is filtration surgery. Laser iridotomy is the preferred method of initial treatment in these unusual cases.

Fig. 8.20 Nanophthalmic eyes have an axial length of less than 20 mm, a small corneal diameter and a normal-sized crystalline lens that is disproportionally large in a small eye. High hyperopia is the norm. They are predisposed to angle closure glaucoma in early to middle age because of crowding of the angle. In this patient B-scan ultrasonography confirms that the axial length is short (15.25 mm) and posterior sclera thicker than average (1.94 mm). Congenital syphilis and mucopolysaccharidoses also predispose to small eyes and increased risk of angle closure glaucoma.

By courtesy of Ms M Restori.

Cellular proliferation with angle closure

Different cell types may be responsible for abnormal cellular proliferation within the angle of the anterior chamber angle leading to obstructed aqueous outflow:

Neovascularization (rubeosis) of the iris and angle with accompanying fibrous tissue formation is the most common type of cellular proliferation causing angle occlusion. It is seen most frequently in diabetic patients or in eyes with an ischaemic central retinal vein occlusion (see Ch. 14). Iris neovascularization may occur less commonly with uveitis, ocular arterial insufficiency, long-standing retinal detachment, intraocular tumours or radiation retinopathy. In all of these conditions the stimulus for neovascularization appears to be retinal hypoxia with the release of vascular endothelial growth factor (VEGF) which stimulates new vessel growth on the iris and in the angle. New vessels appear initially around the pupil margin and in the angle. Contraction of the fibrovascular tissue on the anterior iris surface produces the fixed dilated pupil with ectropion uveae seen in the late stages of the condition. New vessels in the angle are usually followed by PAS formation, outflow obstruction and raised IOP follow.

The extent and rapidity of this process varies with the disease. It typically occurs about 3 months after a severe retinal vein occlusion and extensive retinal hypoxia (‘100-day glaucoma’) and occurs less rapidly in diabetic patients. During the process of neovascularization there may be a massive breakdown of the blood–aqueous barrier with inflammation in the anterior chamber. The patient experiences severe pain in the eye and by the time of presentation the IOP may have risen to very high levels as a result of the development of PAS.

Rubeotic glaucoma

Fig. 8.21 In the early stages (left), neovascularization is seen around the pupil margin as a fine vascular network that does not have a normal anatomical distribution. In an advanced case (right) there is florid neovascularization, corneal oedema and aqueous flare. Pain in these eyes is often due to a combination of inflammation and raised IOP; both can be treated to some degree by topical mydriatics and steroids. Trabeculectomy is rarely successful in such eyes but enucleation may often be avoided by transscleral diode cyclophotocoagulation (cyclodiode) or implantation of an aqueous shunt.

Fig. 8.22 Differentiating neovascularization from dilated iris vessels can sometimes be difficult. (Left) Radial iris vessels might be confused with normal vessels, but gonioscopic examination reveals typical circumferential neovascularization in the angle (right).

Fig. 8.23 Histological examination of the iris in neovascular glaucoma demonstrates a neovascular membrane on the anterior iris surface pulling the iris pigment epithelium on to the anterior surface (ectropion uveae). The angle is occluded by a neovascular membrane with endothelial slide from the corneal surface creating angle closure.

The iridocorneal endothelial (ICE) syndromes

Essential iris atrophy, Chandler’s syndrome and the iris–naevus (Cogan–Reese) syndrome all result from a primary disorder of the corneal endothelium and are different morphological aspects of the same disease process. ICE syndrome is unilateral and sporadic; it occurs in early adulthood and is more common in women. The basic defect appears to be a loss of cell contact inhibition with corneal endothelial cell proliferation and formation of a Desçemet’s-like membrane spreading across the angle and on to the anterior iris surface (see Ch. 6). A demarcation line may be seen on the cornea between normal and abnormal endothelium. Herpes simplex infection has been implicated in the aetiology but antiviral therapy does not appear to influence the disease process.

Chandler’s syndrome is characterized by corneal endothelial cell decompensation and glaucoma producing oedema and early presentation with haloes. The degree of corneal oedema is usually disproportionate to the level of IOP although it is often improved by reducing the IOP. The endothelium that has been completely replaced assumes a ‘hammered silver’ appearance (see Ch. 6). PAS and corectopia (eccentric pupil) are not major features. The increase in IOP does not necessarily correlate with the degree of synechial closure as an open angle may still be occluded by a subclinical ICE membrane.

The iris–naevus syndrome gives the impression of heterochromia due to the presence of iris nodules which are really foci of normal iris stroma protruding through a constricting membrane of endothelial cells on the anterior iris surface. Traction by this membrane produces ectropion uveae. PAS are a characteristic feature. The increased IOP is usually resistant to medical therapy and trabeculectomy usually fails due to ingrowth of ICE membrane; implantion of a drainage device offers the best prospect of longer-term IOP control.

Fig. 8.24 ‘Essential iris atrophy’ is characterized by unilateral glaucoma, corectopia (eccentric pupil), pseudopolycoria and PAS. Migration of endothelium on to the iris produces chronic traction at that point and stretching and eventual hole formation on the opposite side of the iris (pseudopolycoria).

Fig. 8.25 In this patient the prominent feature is the pupillary distortion by an ICE membrane. Less obvious is the iris stromal thinning in the opposite quadrant.

By courtesy of Dr A J W Huang.

Fig. 8.26 This left eye with more advanced disease and intractable glaucoma has had a drainage device implanted. There is marked nasal pseudopolycoria due to the ICE membrane drawing the iris temporally.

Fig. 8.27 Histological appearance shows a surface membrane on the iris stroma with ectropion uveae and angle closure. The glaucoma is usually much worse than would be anticipated by the gonioscopic appearances, reflecting subclinical changes in the angle elsewhere.

Fig. 8.28 This patient with Chandler’s syndrome shows a bullous keratopathy (a prominent feature of the syndrome) together with corectopia and iris atrophy (both of which are less marked than in essential iris atrophy). PAS tend to be less extensive than in essential iris atrophy although the IOP may still be raised.

Fig. 8.29 In the iris–naevus syndrome, iris atrophy is less obvious than in the typical case of essential iris atrophy but there is more corneal oedema. The anterior surface of the iris is covered by a sheet of Desçemet’s membrane-like material through which normal nodules of iris tissue protrude. These have been mistaken for iris melanoma resulting in enucleation. Ectropion uveae is common. In this photograph note the ectropion uveae together with loss of the usual appearance of the anterior iris stroma.

Epithelialization of the anterior chamber

Glaucoma may result from epithelial cells gaining entry into the anterior chamber (epithelial downgrowth). Conditions within the eye needed for epithelial ingrowth are a poorly closed anterior segment wound or implantation of epithelial cell nests into the iris stroma from injury or surgery. Should these conditions occur, epithelial cells proliferate either as a sheet within the chamber or as a slowly growing cyst. Epithelial cysts are generally more benign but may convert to sheet-like downgrowth if inadequately surgically excised. Either can cause angle closure and secondary glaucoma. Sheet-like downgrowth progresses inexorably, first circumferentially around peripheral cornea then across the angle and iris before moving centrally toward the visual axis; eventually it can affect all anterior segment structures, lens and vitreous, and, in vitrectomized eyes, even the retina. If the wound is leaking the eventual sealing by proliferating epithelium causes intractable IOP elevation because epithelium occludes the angle. Membranes that are excised tend to recur despite aggressive en bloc excision and management is usually to control the IOP. This usually necessitates implantation of an aqueous shunt.

Fig. 8.30 In this example a large epithelial anterior chamber cyst has developed after a traumatic perforation at the limbus. Surgical excision of this type of cyst carries a high risk of converting a self-limiting cyst to a more malign sheet-like ingrowth.

Fig. 8.31 In this patient sheet-like epithelial downgrowth has occurred after a secondary intraocular lens implantation to produce a retrocorneal membrane (left) and a membrane on the anterior iris surface (centre). A positive Seidal test is seen at the limbus (right).

By courtesy of Dr W W Culbertson, Bascom Palmer Eye Institute, University of Miami School of Medicine.

Fig. 8.32 Histological examination shows occlusion of the angle by direct spread of epithelial cells over the cornea, inner surface of the trabecular meshwork and iris.

Pigmentary glaucoma

Pigment dispersion syndrome (PDS) is a descriptive term for the deposition of pigment granules derived from the pigment epithelium of the iris onto the structures within the anterior chamber. Thus pigment may be found on the anterior iris surface, the corneal endothelium (Krukenberg’s spindle) or the trabecular meshwork (as a midtrabecular band of pigment); less frequently pigment is seen on the lens equator and zonules following mydriasis. The pigment release occurs from abrasion of the posterior iris surface by zonular fibres; for this to happen, the midperiphery of the iris must be concave posteriorly. This concavity occurs most often in young adult myopic males with a deep anterior chamber. It is hypothesized that accommodation produces a relative negative pressure in the posterior chamber that makes the iris bow backwards resulting in ‘reverse pupil block’. Posterior iris bowing is often visible on gonioscopy. Iridozonular contact and abrasion produce radial slit-like defects in the pigment epithelium which are visible on iris transillumination. The defects may disappear with time if abrasion stops. If sufficient pigment is released to compromise outflow facility the IOP rises (PDS with ocular hypertension); if this persists for long enough glaucoma develops. Reduced trabecular outflow results from chronic loss of trabecular cells with phagocytosed pigment. Large dispersions of pigment occur (pigment storms) can produce swings in IOP.

Treatment with miotics may reduce pigment shedding, although these drugs are not well tolerated by young myopic patients. Peripheral iridotomy can prevent the reverse pupil block and may arrest the process but by the time the IOP becomes raised irreversible trabecular damage has usually occurred and the IOP remains increased. It can be lowered by conventional treatment; approximately one-third of patients eventually require filtration surgery.

An uncommon form of acquired pigmentary glaucoma has been seen with posterior chamber intraocular lens implants where the haptics rub against the posterior iris surface producing pigment release.

Fig. 8.37 In this patient extensive pigment deposition rather like dust particles, is seen on the anterior iris surface lying in the wrinkles formed by iris contraction.

Fig. 8.38 Retroillumination of the iris of the patient in Fig. 8.37 shows multiple slit-like defects in the pigment epithelium of the peripheral iris. Care must be taken in diagnosing pigmentary glaucoma as a number of other conditions also cause peripheral iris transillumination defects.

Fig. 8.39 Krukenberg’s spindle is the term given to pigment deposition on the posterior corneal surface. The pigment is usually deposited in a vertical band.

Fig. 8.40 The angle in PDS is heavily pigmented often through 360°.

Fig. 8.41 The likely mechanism of pigmentary dispersion is abrasion of the peripheral iris pigment epithelium by the anterior zonules which come into contact during episodes of reverse pupil block induced by accommodation in some young myopes. This results in backward bowing of the peripheral iris.

Fig. 8.42 Histological section showing extensive pigment accumulation in the angle. Pigment granules lie freely between the trabecular plates and are phagocytosed within the endothelium or by macrophages. Loss of trabecular endothelial cells results with collapse of normal trabecular meshwork architecture.

Fig. 8.43 Electron micrograph of the angle demonstrates a characteristic accumulation of intertrabecular and intracellular pigment granules that is not seen in age-matched control eyes.

Pseudoexfoliation glaucoma (exfoliation syndrome)

The term pseudoexfoliation has been used to distinguish this condition from true exfoliation of the lens capsule seen following exposure to infrared light (Glassblowers’ cataract), although the latter is extremely rare. Pseudoexfoliation is the descriptive term given to dandruff-like material found on the pupil margin, the anterior lens surface and occasionally the posterior corneal surface. Despite its commonly cited propensity in Scandanavian races pseudoexfoliation has been recorded in virtually every ethnic group. The abnormal material is a glycoprotein derived from a wide range of cells in the anterior lens capsule, the zonules and the inner layer of ciliary epithelium as a result of a generalized basement membrane disorder. Ultrastructurally, pseudoexfoliative material comprises fine fibrils in a matrix. If sufficient material is produced, the outflow facility may be compromised and the IOP increased with eventual glaucoma. The condition is usually bilateral, although asymmetrical. The response to topical glaucoma medication is often poor.

Patients with pseudoexfoliation are usually elderly and have coexistent cataract. Surgical treatment in these patients can usefully be combined with cataract extraction. However, care needs to be taken with cataract surgery because the zonules are weak in these eyes.

Fig. 8.44 In pseudoexfoliation, exfoliated material abraded by the iris from the anterior lens surface collects on the pupil margin where it looks like dandruff. Pigment is also rubbed off the posterior surface of the peripupillary iris and is deposited on the anterior iris surface and in the iridocorneal angle. This eye also shows widespread pigment deposition on the anterior iris surface.

Fig. 8.45 Pupillary abrasion creates a characteristic zone free of pseudoexfoliative material. With further mydriasis the abnormal material can be seen on the anterior lens surface.

Fig. 8.46 Extensive pigment deposition can be seen in the angle.

Fig. 8.47 Histological appearance shows eosinophilic pseudoexfoliative material on the anterior lens capsule and posterior surface of the iris. The angle contains more pigment than usual together with the fibrillar material caught up in the meshwork. This material can also be found histologically around the conjunctival vessels.

Fig. 8.48 Electron microscopy reveals the characteristic fibrillar material in the intertrabecular spaces.

By courtesy of Professor D H Johnson

Lens-induced glaucoma (phacolytic glaucoma)

The lens capsule of a hypermature cataract may leak denatured cortical material. This is particularly common with Morgagnian cataracts which should be removed to forestall this complication (see Ch. 11). Leakage in turn excites a macrophage response; the macrophages, gorged with lens material accumulate and clog the trabecular meshwork causing a secondary open-angle glaucoma known as phacolytic glaucoma. Much more common today is ‘lens fragment-related glaucoma’ in which retained fragments of lens nucleus after cataract surgery cause increased IOP after surgery. Retained fragments should be carefully looked for in these eyes with gonioscopy especially in the inferior angle where they may be missed and offending lens matter should be removed.

Fig. 8.49 Histological examination demonstrates lens-filled macrophages obstructing the angle and trabecular meshwork. Low magnification (left) and higher magnification (right) of lens-filled macrophages. Clinically these are seen as large accumulations floating in the anterior chamber of an eye with a mature cataractous lens and acute glaucoma, an open angle and a deep anterior chamber.

Fig. 8.50 Retained fragments of lens nucleus or cortex from complicated cataract surgery can cause an intractable increase in IOP and recurrent inflammation. Here, a fragment of cortex is visible in the inferior angle, even without gonioscopy. Removal of retained cortex usually improves control of both the IOP and intraocular inflammation.

Fig. 8.51 This anterior chamber contains both viscoelastic and silicone oil after combined cataract and vitreoretinal surgery. In the upright position the silicone oil is prevented from rising to the top of the anterior chamber by the retained viscoelastic. Here, it is retained viscoelastic that is causing the increased IOP after vitreoretinal surgery; its removal by anterior chamber washout should improve IOP control.

Fig. 8.52 A typical hyperoleum of emulsified silicone oil following vitreoretinal surgery in an aphakic eye.

Fig. 8.53 Prolonged presence of emulsified silicone oil in the anterior chamber can cause a destructive chronic giant cell reaction in the angle structures.

By courtesy of Mr R Azaria.

Haemolytic glaucoma

Blood cells and their degeneration products may cause secondary open-angle glaucoma. Under normal conditions healthy red blood cells pass through the trabecular meshwork to enter Schlemm’s canal. If the trabecular meshwork becomes clogged by these cells the IOP will rise. With a healthy angle elimination of hyphema is followed by return of the IOP to normal. Haemolytic glaucoma is caused by erythroclasts left after the absorption of haemoglobin from red cells. The reduced malleability of ghost cells renders them more difficult to remove through the meshwork. It should be suspected when open-angle glaucoma is discovered in an eye with a long-standing vitreous haemorrhage and minimal uveitis with yellowish discoloration within the anterior and posterior chambers, especially if it is aphakic. Phase-contrast microscopy may be used to identify these degenerate red blood cells (ghost cells) on aqueous tap.

Fig. 8.54 The histological appearance of the trabecular meshwork in haemolytic glaucoma shows degenerated red blood cells (ghost cells) on the trabecular spaces and within macrophages.

By courtesy of Professor I Grierson.

Siderosis

Siderosis results from the widespread deposition of iron throughout the eye diffusing from a retained ferrous ocular foreign body. Glaucoma occurs secondary to sclerosis of the trabecular meshwork which is thought to be a direct toxic effect. Clinically eyes with siderosis demonstrate mydriasis, heterochromia and retinal degeneration with optic atrophy as well as raised IOP. The ERG shows specific changes depending on the degree of retinal damage.

Fig. 8.55 The right eye of this patient shows evidence of siderosis with brown-green discoloration of the iris from iron deposition.

Fig. 8.56 Histological examination shows iron deposition within the meshwork and Schlemm’s canal associated with loss of normal trabecular architecture. There is a reduction in the number of trabeculocytes together with trabecular collapse.

Tumour infiltration

About 5 per cent of eyes with tumours develop glaucoma either as a result of angle closure from forward movement of the lens–iris diaphragm (see Fig. 8.10), neovascularization or invasion of the angle by tumour causing secondary open-angle glaucoma. Less commonly, a malignant melanoma arising from the iris root and ciliary body may invade the angle directly to produce glaucoma. On very rare occasions ‘melanomalytic’ glaucoma arises from trabecular obstruction by macrophages engorged with melanin from a necrotic tumour.

Fig. 8.57 Gonioscopic view shows an iris melanoma occluding the angle.

Fig. 8.58 Histological appearance shows infiltration of the angle and trabecular meshwork by melanoma cells from an iris melanoma.

Fuchs’ heterochromic cyclitis (see also Ch. 10)

This chronic nongranulomatous uveitis is almost always unilateral. Patients usually present complaining of floaters but later vision is reduced as a result of cataract. Iris atrophy (the affected iris has anterior stromal atrophy and a lighter colour) and iris nodules, fine widespread keratic precipitates, cataract, glaucoma and occasionally a fine neovascularization of the angle are all seen in established cases (see Ch. 10). Neither anterior nor posterior synechiae develop. The glaucoma responds to conventional medical or surgical treatment and the eye responds well to cataract surgery should it be indicated. The uveitis responds poorly to steroids.

Fig. 8.59 A patient with heterochromic cyclitis of the right eye. The affected iris is depigmented and a cataract is present.

Fig. 8.60 Iris depigmentation and transillumination is seen with long-standing cyclitis. The keratic precipitates in Fuchs’ heterochromic cyclitis look unusual; typically they are distributed across the entire corneal surface and are often interconnected by a fine network of filaments.

Posner–Schlossman syndrome (glaucomatocyclitic crisis)

This unusual condition is typically seen in young adult men who develop very high levels of IOP with minimal anterior uveitis that is self-limiting. The syndrome is usually uniocular. Patients present with blurring and haloes from corneal oedema due to an IOP in the 40–60 mmHg range. The uveitis is minimal and typically only one sentinel keratic precipitate or, at most, a small number of keratic precipitates are visible. Posterior synechiae do not form. Occasionally, after many attacks, chronic increase in IOP occurs from permanent damage to the meshwork either directly from the disease process or secondary to raised IOP causing degenerative changes in the meshwork. Whatever the mechanism, a condition clinically indistinguishable from primary open-angle glaucoma develops. Acute attacks typically last for days. Herpes simplex and secretion of prostaglandins have been implicated in the aetiology.

Fig. 8.61 Sentinel keratic precipitates seen during the quiescent phase. There is some evidence that the increased IOP is associated with high levels of aqueous humour prostaglandins.

Steroid-induced glaucoma

Chronic topical steroid usage causes raised IOP in a proportion of patients. There is some evidence that the steroid response in this population is determined genetically and may be similar to those in patients at risk of primary open-angle glaucoma, possibly by stressing an already compromised angle. The glaucoma usually appears after a few weeks of treatment and this complication must be taken into consideration in any patient on topical steroid therapy. In most cases IOP falls to normal on cessation of the topical steroid. Different steroid preparations vary in their ability to produce this phenomenon; the degree of response is related to their potency and penetration of the cornea and to their potential for hydrolysis within the aqueous humour. The exact mechanism is uncertain but it is known that glucocorticoids influence cell size, behaviour and cytoskeletal organization, extracellular matrix turnover and composition of the trabecular meshwork. Meshwork cells exposed to steroids produce myocilin which is encoded by the gene GLC1A, mutations of which are responsible for most cases of autosomal dominant juvenile open-angle glaucoma. Histologically, intertrabecular spaces are blocked by a fibrillar material.

Fig. 8.62 Glaucomatous cupping, more advanced on the left than in the right, is seen in this patient who had used topical steroids without supervision for treatment of mild ocular irritation associated with contact lens wear.

Fig. 8.63 Electron micrograph of the corneal scleral meshwork in a patient with steroid-induced glaucoma showing the intertrabecular spaces filled with fibrillar material. In some areas the trabecular lamellae are not completely covered with endothelial cells.

Courtesy of Professor E Lutjen-Drecoll.