Ординатура / Офтальмология / Английские материалы / Shields Textbook of Glaucoma, 6th edition_Allingham, Damji, Freedman_2010

Figure 16.10 Membrane theory of Campbell for pathogenesis of ICE syndrome. A: Extension of the membrane from the corneal endothelium over the anterior chamber angle and onto the iris. B: Contraction of the membrane, creating peripheral anterior synechiae and corectopia. C: Thinning and atrophy of iris in quadrants away from the corectopia. D: Hole formation in an area of atrophy (in progressive iris atrophy), ectropion uvea in the direction of the corectopia, and nodules in the area of the membrane (in Cogan-Reese syndrome). (From Shields MB. Progressive essential iris atrophy, Chandler syndrome, and the iris nevus [Cogan-Reese] syndrome: a spectrum of disease. Surv Ophthalmol. 1979;24(1):3-20, with permission.)

Among the category of nodular lesions of the iris, melanomas of the iris (20); iris melanosis, which may be familial (21); Lisch nodules seen in neurofibromatosis type 1 (22); bilateral diffuse iris nodular nevi (23); and nodular inflammatory disorders, such as sarcoidosis, may also have pedunculated nodules strikingly similar to those of the Cogan-Reese syndrome.

Management

Patients with ICE syndrome may require treatment for corneal edema, the associated glaucoma, or both during the course of the disease. Given the unpredictable biological behavior of the abnormal corneal endothelium, patients with ICE syndrome should be monitored regularly based on signs and symptoms of the disease. For instance, one case has been reported in which the pigmented nodules appeared on the iris 20 years after the initial diagnosis of ICE syndrome (24). Although specular microscopy can help to diagnose ICE syndrome, the findings do not correlate with the degree of corneal edema or decompensation or with the level of IOP elevation (25).

In the early stages, the glaucoma can often be controlled medically, especially with drugs that reduce aqueous production. When the IOP can no longer be controlled medically, surgical intervention is indicated, and a high percentage of patients with the ICE syndrome eventually require surgery. Given the membrane theory of this disease (Fig. 16.10), laser trabeculoplasty is not effective for this disease and is not recommended as treatment. In one study of 66 patients, glaucoma occurred in 33 (50%), and 22 (66%) of these underwent surgery; 45% of the patients who had a trabeculectomy required more than one procedure (26). Filtering surgery is reasonably successful, although late failures have occurred because of endothelialization of the filtering bleb (27). Adjunctive use of 5-fluorouracil did not improve

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outcomes (28). Adjunctive mitomycin C has been reported to offer reasonable intermediate-term success (29). Another surgical option is glaucoma drainage-device surgery (30). However, repeated filtering procedures, glaucoma drainage-device revision, and cyclodestructive laser may be additional options to lower IOP if previous surgical interventions have failed.

The corneal edema may be improved by lowering the IOP, although the additional use of hypertonic saline solutions may be required. However, in corneas with marked dysfunction of the endothelium, the edema will not clear, and penetrating keratoplasty is usually indicated for this situation after the glaucoma has been controlled (31). In one series of 14 patients who had ICE syndrome treated by penetrating keratoplasty, repeated corneal grafts were required in 6 (43%) over an average followup of 58 months (32). In the future, the development of therapies can be directed more specifically at the underlying disease process. For example, if the theory of a viral cause proves to be correct, it may allow treatment with antiviral agents. Another approach may be to prevent the growth of the endothelial membrane. An immunotoxin has been described that inhibits the proliferation of human corneal endothelium in tissue culture.

POSTERIOR POLYMORPHOUS CORNEAL DYSTROPHY General Clinical Features and Terminology

Posterior polymorphous corneal dystrophy is a rare, bilateral, autosomal dominant familial disorder of the corneal endothelium. Presently, the three genes that have been identified for PPMD are COL8A2 on chromosome 1p34.3 (33), ZEB1 (formerly called TCF8) on chromosome 10p11.2 (34), and VSX1 on chromosome 20p (35) (Chapter 8).

Figure 16.11 Slitlamp image of a patient with PPMD shows typical, irregular vesicular lesion of the posterior corneal surface (A) and subtle snail track across the central cornea (B).

In general, the clinical features of PPMD include symptoms presenting in young adulthood and a clinical spectrum of characteristic corneal changes, peripheral iridocorneal adhesions, iris atrophy, and corectopia (discussed in detail later). Glaucoma occurs in approximately 15% of patients with PPMD (36).

Pathologic Features Changes in the Cornea

By slitlamp biomicroscopy, the posterior cornea has the appearance of blisters or vesicles at the level of Descemet membrane (Fig. 16.11A). The vesicles may be linear (Fig. 16.11B) or in groups and may be surrounded by an aureole of gray haze (36). Band-like thickenings may also be seen at the level of Descemet membrane (37). On specular microscopy, several abnormal patterns have been described:

either vesicles and band patterns at the level of Descemet membrane or a geographic pattern with associated haze of Descemet membrane and deep corneal stroma (38). An interesting observation was that 48 patients with PPMD, who had classic vesicles alone (42%) or vesicles with bands (48%) or diffuse abnormality of Descemet membrane (10%), had no other ocular abnormalities other than those of the cornea (39). In contrast, the latter specular pattern of prominent haze of Descemet membrane appears to be associated more with iridocorneal adhesions and glaucoma (38).

Ultrastructural studies reveal an unusually thin Descemet membrane covered by multiple layers of collagen and lined by cells that have been described as abnormal endothelium with epithelial-like and fibroblast-like features (40, 41 and 42). In an unusually aggressive form of PPMD, a patient underwent 25 ocular procedures over 17 years for glaucoma, cataract, cornea, retina, and postoperative problems (43). Electron microscopy

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on the cornea revealed microvilli, tonofilaments, and desmosomes consistent with endothelial transformation (Fig. 16.12), which was confirmed by positive anticytokeratin AE1/AE3 and CAM 5.2 immunoreactivity. Negative immunoreactivity in epithelium and positive in endothelium with anticytokeratin 7 supported the diagnosis of PPMD rather than epithelial downgrowth.

Figure 16.12 Transmission electron microscopy of left corneal button from a patient with PPMD showed stratified endothelial cells with nuclei, microvilli, and desmosomal attachments.

Changes in the Iris, Angle, and Lens

A small number of patients may have broad peripheral anterior synechiae extending to or beyond the Schwalbe line, which may be associated with corectopia, ectropion uvea, and atrophy of the iris (Fig. 16.13) (36, 44). The glaucoma may be caused by the iridocorneal adhesions in these cases. However, the extent of the iridocorneal adhesions does not correlate with the presence or severity of glaucoma, because the adhesions that bridge an otherwise open trabecular meshwork may not obstruct aqueous outflow (45). Histopathologic studies of such cases have revealed a membrane composed of epitheliallike cells and a Descemet-like membrane extending over the anterior chamber angle and onto the iris (43, 44). Three types of peripheral anterior synechiae have been described: without an associated membrane, with iridotrabecular and iridocorneal apposition, and bridging open trabecular meshwork (45). The abnormal membrane is associated with the latter two configurations.

Figure 16.13 Slitlamp image showing corectopia, ectropion uvea, and focal iris atrophy of the right eye in a patient with PPMD. (Modified from Moroi SM, Gokhale PA, Schteingart MT, et al. Clinicopathologic correlation and genetic analysis in a case of posterior polymorphous corneal dystrophy. Am J Ophthalmol. 2003;135(4):461-470, with permission.)

Glaucoma may be present in some of the cases with peripheral anterior synechiae, but it has also been observed in eyes with open angles (46). In the latter situation, gonioscopy may reveal a high insertion of the iris into the posterior aspect of the trabecular meshwork. An ultrastructural evaluation of such an eye confirmed the high insertion of anterior uvea into the meshwork with collapse of the trabecular beams. In the particularly aggressive form of PPMD described earlier, a prominent retrocorneal membrane grew onto the crystalline lens and intraocular lens (43).

Theories of Mechanism

A membrane theory, similar to that for the ICE syndrome, has been proposed for cases of PPMD. It is postulated that a metaplastic endothelium shows features of epithelial cells, loses contact inhibition, produces a basement membrane-like material, extends across the anterior chamber angle and onto the iris, and leads to synechia formation and changes in the iris (36, 47). The mechanism of glaucoma in eyes with PPMD may be due to either a closed-angle mechanism from the membrane alone or from the synechia formation (45), or the less common observation of open-angle mechanism with the high insertion of the anterior uvea that represents a developmental anomaly of the anterior chamber angle, as seen in several of the developmental glaucomas (46).

Among the three causative genes for PPMD—VSX1, COL8 A2, and ZEB1 (formerly called TCF8)— transcripts for all three genes have been demonstrated in the cornea (34). ZEB1 (formerly called TCF8), accounts for about one third of PPMD familial cases (48). In the initial family used to identify ZEB1 as the PPCD3 gene, inguinal hernia, hydrocele, and possible bone anomalies in affected individuals were also reported (34). The association with hernias was also replicated in another study (48). A potential molecular mechanism was suggested by the ectopic expression of COL4A3, which is collagen type IV alpha 3, in corneal endothelium of the proband of the original PPCD3 family. Mutations in the COL4A3 gene cause Alport syndrome, and ZEB1 has a complex binding site in the promoter of Alport syndrome gene COL4A3. It was proposed that the loss of function of ZEB1 allowed for expression of COL4A3, a regulatory target for ZEB1, and contributes to the molecular mechanism for endothelial dysfunction in PPMD (34).

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Differential Diagnosis

Conditions that may be confused with PPMD include other forms of posterior corneal dystrophy, such as Fuchs endothelial dystrophy, congenital hereditary corneal dystrophy, and posterior amorphous corneal dystrophy. The last condition is characterized by diffuse gray-white, sheet-like opacities of the posterior stroma, with occasional fine iris processes extending to the Schwalbe line for 360 degrees and various abnormalities of the iris but no glaucoma (49). When iridocorneal adhesions are present, AxenfeldRieger syndrome and ICE syndrome should be considered. The band-like thickenings of PPMD may be confused with the Haab striae of congenital glaucoma, although the latter are distinguished by the characteristic thinned areas with thickened edges (37).

Management

Most cases of PPMD are asymptomatic and do not require treatment. Corneal edema may require conservative management or penetrating keratoplasty. In one series of 21 keratoplasties for PPMD, 9 grafts failed, 6 of which were associated with iridocorneal adhesions and glaucoma, and it has been suggested that keratoplasty should be avoided in these patients until absolutely necessary (47). Recurrence of PPMD has been reported after penetrating keratoplasty. The glaucoma may respond to drugs that lower aqueous production. Laser trabeculoplasty is not likely to be successful in these cases, and filtering surgery, glaucoma drainage-device surgery, or laser cyclodestruction is indicated when medical therapy is no longer adequate. PPMD is a common feature of Alport syndrome, a basement membrane disorder with hereditary nephritis, sensorineural hearing loss, anterior lenticonus, and retinal flecks (50). Management of patients with PPMD should include an examination for renal abnormalities and hearing loss and hernias (34, 50).

FUCHS ENDOTHELIAL CORNEAL DYSTROPHY General Clinical Features and Terminology

Cornea guttata is a common and typically asymptomatic condition that increases significantly with age (51). Slitlamp biomicroscopy reveals a beaten-silver appearance of the central posterior cornea, similar to that seen in the ICE syndrome.

When patients who have the same posterior corneal changes as described earlier develop edema of the corneal stroma and endothelium, it is called Fuchs endothelial dystrophy (52). The condition may lead to severe visual reduction, often requiring penetrating keratoplasty. The disorder is bilateral with a

predilection for women and an onset usually between the ages of 40 and 70 years (53). There is a strong familial tendency, and an autosomal dominant inheritance pattern has been described (54). The gene for Fuchs endothelial corneal dystrophy, COL8A2, was identified on chromosome 1p (see Chapter 8).

Reports are conflicting regarding the association of openangle glaucoma with corneal guttata and Fuchs endothelial dystrophy. However, a study of 64 families with Fuchs endothelial dystrophy revealed only one case of open-angle glaucoma (55). Acute elevations of IOP cause secondary changes in the corneal endothelium with edema in the stroma and epithelium. Reduced cell densities have been reported in association with ocular hypertension, angle-closure glaucoma, exfoliative glaucoma, and glaucomatocyclitic crisis (56, 57, 58 and 59). However, the degree of endothelial alteration does not always correlate with the height of IOP elevation, suggesting that other factors, such as aging and inflammation (60, 61), also influence the association between glaucoma and corneal endothelial changes.

There is more evidence for an association of angle-closure glaucoma and Fuchs endothelial corneal dystrophy. Patients with Fuchs corneal endothelial dystrophy have a higher incidence of angle-closure glaucoma due to axial hypermetropia and shallow anterior chambers (62, 63).

Pathologic Features

On specular microscopy, there is a characteristic pattern of enlarged corneal endothelial cells with dark areas that overlap the cell borders (64). The primary pathology is an alteration in the corneal endothelium that leads to a deposition of collagen on the posterior surface of Descemet membrane, which on histology appear as warts or excrescences in the pure form of cornea guttata or may be covered by additional basement membrane or there may be a uniform thickening of the posterior collagen layers (65).

Theories of Mechanism

Aqueous humor dynamic studies have shown that aqueous humor composition is normal (66). In a study using wide-field specular microscopy, the mean value for facility of outflow was similar between patients with cornea guttata and controls (67). Thus, the normal aqueous humor dynamic studies support that Fuchs endothelial dystrophy is a primary disorder of the corneal endothelium.

Differential Diagnosis

Clinically, the corneal endothelial changes in Fuchs endothelial dystrophy may resemble those in exfoliation keratopathy (Chapter 15). However, the latter typically has fewer guttatalike structures that are more diffusely distributed. Exfoliation syndrome is associated with more melanin dispersion in the anterior segment and peripupillary iris atrophy.

Management of Glaucoma

Although glaucoma is usually not present in eyes with Fuchs endothelial dystrophy, reducing IOP may sometimes help to minimize the corneal edema. The use of topical carbonic anhydrase inhibitors should be avoided, because cases of further compromise of the cornea with this class of glaucoma medications have been reported (68). When glaucoma is present, the open-angle form is managed in the same manner as chronic

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open-angle glaucoma, but the angle-closure form requires an iridotomy or filtering procedure. KEY POINTS

ICE syndrome is a primary disorder of the corneal endothelium, which manifests in young adulthood as a unilateral abnormality of the cornea, anterior chamber angle, and iris. It appears to be an acquired condition, possibly caused by a virus.

The abnormal endothelium in ICE syndrome often causes corneal edema and proliferates over the angle and iris with subsequent contraction, leading to glaucoma and variable degrees of iris distortion. The latter changes are the basis for clinical variations, including Chandler syndrome, progressive iris atrophy, and the Cogan-Reese syndrome.

PPMD is another spectrum of disease in which an endothelial abnormality is the fundamental

disorder. Glaucoma is present in a small percentage of these cases, and in some patients, a proliferation of the abnormal endothelium causes changes of the anterior chamber angle and iris, resembling those in the ICE syndrome. The condition differs from the latter syndrome, however, in that it is inherited and bilateral and has a different clinical appearance of the posterior cornea.

A third primary disorder of the corneal endothelium, Fuchs endothelial dystrophy, occasionally has associated glaucoma, usually with an angle-closure mechanism.

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Shields > SECTION II - The Clinical Forms of Glaucoma >

17 - Pigmentary and Other Glaucomas Associated with Disorders of the Iris and Ciliary Body

Authors: Allingham, R. Rand

Title: Shields Textbook of Glaucoma, 6th Edition Copyright ©2011 Lippincott Williams & Wilkins

> Table of Contents > SECTION II - The Clinical Forms of Glaucoma > 17 - Pigmentary and Other Glaucomas Associated with Disorders of the Iris and Ciliary Body

17

Pigmentary and Other Glaucomas Associated with Disorders of the Iris and Ciliary Body IRIS OR CILIARY BODY DISORDERS WITH ASSOCIATED GLAUCOMA

There are several conditions in which a disorder of the iris or ciliary body is believed to be involved in the initial events that eventually lead to various forms of glaucoma (Table 17.1). Most of these, such as developmental disorders, inflammatory conditions, and intraocular tumors, are considered in other chapters in Section II. In this chapter, we consider additional conditions—pigmentary glaucoma, iridoschisis, plateau iris, pseudoplateau iris, and swelling of the ciliary body—that do not fit preci sely into any of these general systems of disease.

PIGMENTARY GLAUCOMA Terminology

As a normal feature of maturation and aging, a variable amount of uveal pigment is chronically released and dispersed into the anterior ocular segment. This is best appreciated by observing the trabecular meshwork, which is nonpigmented in the infant eye but becomes progressively pigmented to various degrees with the passage of years because of the accumulation of the dispersed pigment in the aqueous outflow system. There is therefore a spectrum of ocular pigment dispersion in the general population. As can be anticipated, this spectrum of pigment dispersion is also found among individuals with various forms of glaucoma, although the pigment in most of these cases is not believed to be a major factor in the mechanism of the glaucoma. Several ocular conditions are associated with an unusually heavy dispersion of pigment, which may be significantly involved in the increased resistance to aqueous outflow. In 1940, Sugar (1) briefly described one such case with marked pigment dispersion and glaucoma. In 1949, Sugar and Barbour (2) reported the details of this entity, which differed from other forms of pigment dispersion by typical clinical and histopathologic features. They referred to the condition as pigmentary glaucoma (2). When the typical findings are encountered without associated glaucoma, the term pigment dispersion syndrome (PDS) has been advocated (3).

General Features

The typical patient is young, myopic, and male. The disorder appears most frequently in the third decade of life, and there is a tendency for it to decrease in severity or disappear in later life (4, 5). Most studies agree that PDS is more common among men, with a male-to-female ratio of approximately 2:1, although studies differ on the ratio of those converting to pigmentary glaucoma (3, 4, 5, 6, 7, 8, 9, 10 and 11). The reason for the male predilection appears to be the sex difference in anterior chamber depth, which one study showed to be 3.22 ± 0.42 mm in men and 2.88 ± 0.38 mm in women (12). (The significance of chamber depth in the mechanism of pigment dispersion is discussed later in this chapter.)

Pigmentary glaucoma is seen predominantly in whites (3, 4, 5, 6, 7, 8, 9, 10 and 11), although it may be more common among blacks than previously recognized (13). In black patients, signs of PDS may be overlooked because dark, thick iris stroma may obscure transillumination defects and pigment granules on the stroma; corneal endothelial pigmentation may be minimal or absent; and greater degrees of trabecular meshwork pigmentation may be interpreted as normal in black patients. It has been suggested that pigment accumulation on the lens zonules and equatorial or posterior lens regions may be particularly helpful in making the diagnosis of PDS in black patients (13). In one report, 20 black