Ординатура / Офтальмология / Учебные материалы / Atlas of Glaucoma Second Edition Choplin Lundy 2007

diabetic neovascularization of the retina, hemorrhage secondary to trauma or a postsurgical hyphema with spill-over into the vitreous through a compromised vitreous face may evolve into a secondary glaucoma. After several weeks, the degenerated cells migrate into the anterior chamber through a defect in the vitreous face (surgical or traumatic) and obstruct the trabecular meshwork. Tan or khaki-colored cells are seen in the anterior chamber, anterior vitreous, on the trabecular meshwork, and may also form a pseudohypopyon. If the vitreous face is intact, the ghost cells do not reach the anterior chamber and glaucoma does not develop.

Several other blood-related elevations of IOP may be differentiated from ghost-cell glaucoma. Hyphemas may result in acutely elevated pressure, especially in patients with sickle-cell disease. This is secondary to obstruction of the meshwork by red blood cells in the first days following the hyphema. Rarely, an eight-ball, total hyphema may persist long enough to contain ghost cells which add to the trabecular obstruction. Hemolytic glaucoma occurs when the contents of ruptured red blood cells are ingested by macrophages which then obstruct the meshwork. Hemolytic glaucoma is also typically seen in the first days to weeks following the initial hemorrhage. Hemosiderotic glaucoma, in which iron-containing blood breakdown products stain and poison the cells of the trabecular meshwork, occurs much later, often years after the hemorrhage.

Aqueous suppressants often control the intraocular pressure. Miotics are rarely helpful as the meshwork is obstructed; similarly, argon laser trabeculoplasty is not indicated. Anterior chamber lavage with balanced salt solution may resolve the glaucoma. If unsuccessful, or too great a reservoir of ghost cells remains in the vitreous, total vitrectomy,

removing as much hemorrhagic material as possible, is usually effective in resolving the glaucoma.

INFLAMMATORY GLAUCOMAS

Inflammation within the eye alters aqueous humor dynamics and can lead to increased IOP. Acute inflammation may reduce aqueous secretion and increase uveoscleral outflow, reducing IOP. However, inflammatory material, consisting of white blood cells, macrophages, and proteins, may obstruct the trabecular meshwork. Chemical mediators of inflammation may further compromise trabecular function as may trabeculitis (inflammation of the trabecular meshwork itself). Trabecular dysfunction may be transient, clearing with resolution of the inflammation, or may persist with permanent structural changes reducing trabecular outflow facility. Additionally, inflammatory scarring may lead to peripheral anterior synechiae and posterior synechiae resulting in angle-closure glaucoma (see Chapter 11). Chronic uveitis may lead to neovascularization and neovascular glaucoma. Patients may manifest some or all of these findings, the balance dictating the nature of the glaucoma. For example, a patient may present acutely during a uveitic episode with uveitic hypotony, progress to a secondary open-angle glaucoma as white blood cells block the meshwork, develop an angle-closure component as synechiae form, and then be left with a chronic mixed-mechanism secondary glaucoma with residual synechiae and scarring of the meshwork.

Virtually all sources of ocular inflammation can lead to glaucoma. Idiopathic uveitis (Figure 10.23), glaucomatocyclitic crisis (Figure 10.24), Fuch’s heterochromic cyclitis (Figure 10.25), lens-related uveitis (Figure 10.26), herpes (Figure 10.27) and

coma with closed and open-angle components. Note the multiple peripheral iridectomies for previous acute iris bombé. Following resolution of acute attacks the patient had persistent elevation of intraocular pressure in spite of large areas of open anterior chamber angle on gonioscopy.

Figure 10.25 Fuch’s heterochromic cyclitis. Note the much lighter iris color in the involved eye. The triad of heterochromia, uveitis and cataract typically appears in the third to fourth decade. The uveitis is asymptomatic. Open-angle glaucoma is common, increasing with duration of the disease. Friable angle vessels may bleed easily with surgery; however, frank neovascularization of the iris and neovascular glaucoma are uncommon.

sarcoidosis (Figure 10.28) may all result in increased IOP. Other uveitic glaucomas include HLA-B27- related uveitides, pars planitis, sarcoidosis, juvenile rheumatoid arthritis, Behçet’s disease, Crohn’s disease, syphilis, toxoplasmosis, coccidiomycosis, mumps, rubella, leprosy, sympathetic ophthalmia, Vogt–Koyanagi–Harada syndrome and other less common entities.

Treatment strategies are similar for these entities. Resolution of inflammation is the first goal,

syndrome). Unilateral involvement consisting of fine keratic precipitates in a patient with minimal anterior chamber reaction and markedly elevated intraocular pressure. Following multiple similar attacks, the patient developed chronically elevated intraocular pressure and optic nerve damage requiring trabeculectomy.

which may require topical or systemic steroids, antibiotics for infectious diseases and lens extraction in lens-related conditions. Increased intraocular pressure secondary to steroid therapy or to increased aqueous production with resolving inflammation may confuse the clinical picture. Cycloplegics are effective through many mechanisms. Dilatation prevents the formation of a small secluded pupil and relieves the discomfort of ciliary spasm. Cycloplegics also improve uveoscleral outflow and stabilize the blood–aqueous barrier. Topical and systemic aqueous suppressants are effective. Miotics should be avoided as these agents cause increased breakdown of the blood–aqueous barrier, making the inflammation worse, and also reduce uveoscleral outflow. Laser trabeculoplasty is generally ineffective and increases inflammation. Filtering surgery is less successful in these patients, especially during acute attacks. Adjunctive use of antimetabolites such as 5-fluorouracil and mitomycin-C may improve results. Drainage tube implants may also be effective. Cyclodestructive procedures can be used in refractory cases, but add to intraocular inflammation and pose significant risks to vision.

GLAUCOMA ASSOCIATED WITH

OCULAR TUMORS

Benign and malignant intraocular tumors may cause glaucoma by a variety of mechanisms. Direct infiltration of the trabecular meshwork by the tumor can block aqueous outflow. Free-floating tumor cells may obstruct the meshwork. Hemorrhage may produce a secondary open-angle glaucoma.

Tumor-related neovascularization of the iris and angle produces glaucoma in some cases. Large posterior masses sometimes press the iris and lens anteriorly, resulting in angle closure (Chapter 11). Tumor-related glaucomas are typically unilateral. Treatment of the glaucoma without diagnosis of the tumor may have serious consequences for the patient. A thorough examination will reveal most intraocular malignancies, especially for clinicians alert to such tip-offs as a sentinel vessel (Figure 10.29).

Uveal melanoma is the most common intraocular malignancy in adults, and is the most common cause of tumor-related glaucoma. Iris melanomas may obstruct the trabecular meshwork by direct

invasion or by hemorrhage (Figure 10.30). Ciliary body melanomas may be more difficult to detect, remaining hidden until relatively large. Glaucoma most often results from the tumor pushing the iris anteriorly to close the anterior chamber angle. Glaucoma may also result because of direct extension of the tumor into the trabecular meshwork, iris neovascularization, hyphema or tumor necrosis, causing obstruction of the meshwork by cells and debris. Choroidal melanoma less commonly causes glaucoma. Mechanisms of glaucoma in choroidal melanomas include iris and angle neovascularization most commonly, as well as angle closure, hemorrhage and necrosis.

Figure 10.27 Herpes zoster ophthalmicus. Herpes zoster ophthalmicus with characteristic skin lesions affecting the dermatome of the first branch of the facial nerve. The tip of the nose is involved, a harbinger of ocular involvement (Hutchinson’s sign). Marked conjunctival injection and a granulomatous uveitis are present. Glaucoma is a frequent complication in herpes zoster and herpes simplex uveitis.

Figure 10.28 Sarcoid uveitis with posterior synechiae and cataract. Up to one-half of patients with sarcoid suffer from uveitis at some point during the disease process. Granulomatous anterior uveitis is a common manifestation, frequently becoming bilateral, recurrent and chronic. Sarcoid nodules on the iris (Busacca’s in the crypts, Koeppe’s at the pupillary margin) may be seen. Secondary open and closed-angle glaucoma is common. As the disease is more common in Blacks, clinicians must be wary of steroid-induced glaucoma as a complication of treatment.

Histologically benign tumors of the iris may also cause glaucoma. Diffuse uveal melanomas may block the meshwork with melanoma cells or pigment. Melanocytomas, most commonly found on the optic disc but also seen in the iris or ciliary body, can produce glaucoma. These tumors have a propensity to undergo necrosis and fragmentation, blocking the trabecular meshwork with debris, producing the so-called melanomalytic glaucoma. Differentiation of these tumors from their malignant counterparts is a crucial step in treatment, often

requiring histopathologic study. Intraocular metastases are typically to the uveal tissues. Glaucoma is found more frequently in metastases to the iris and ciliary body (64% and 67%, respectively) than in metastases to the choroid (2%). Common primary tumors include those of the breast and lung, as well as tumors of the gastrointestinal tract, kidney, thyroid and skin. Efforts to identify the primary neoplasm are not always successful. Friable metastases often seed the anterior chamber angle, obstructing the trabecular meshwork (Figures 10.31 and 10.32).

Pseudohypopyons and ring infiltrates are sometimes seen.

Benign reactive lymphoid hyperplasia can directly invade the trabecular meshwork. Large cell lymphoma (reticulum cell sarcoma, histiocytic lymphoma) and leukemia may also infiltrate the meshwork and lead to glaucoma.

Retinoblastoma is the most common intraocular malignancy of childhood. Glaucoma is not uncommon, occurring in 17% of cases in one study (Shields et al.). In that study of 303 eyes, the glaucoma was thought to be secondary to iris neovascularization with or without hemorrhage in 72%, angle closure in 26%, and tumor seeding in 2% (Figure 10.33). The less common but benign medulloepithelioma may also cause glaucoma secondary to iris neovascularization, as well as direct invasion of angle structures or obstruction of the meshwork by hyphema and tumor-related debris.

Various ocular tumors are manifested by the phakomatoses. Unilateral glaucoma, congenital or later onset, may be seen in neurofibromatosis of

both types (Figure 10.34). Half of all eyes with plexiform neuromas of the upper lid develop glaucoma. The glaucoma associated with encephalotrigeminal angiomatosis (Sturge–Weber syndrome) is discussed below, along with other causes of increased episcleral venous pressure. Congenital glaucoma may also be seen. Oculodermal melanocytosis (nevus of Ota) has been reported to have an incidence of glaucoma of 10%, including angle-closure, open-angle and congenital varieties.

INCREASED EPISCLERAL VENOUS

PRESSURE

The Goldmann equation, Po F/C Pev (where Po is intraocular pressure, F is aqueous production, C outflow facility and Pev episcleral venous pressure), describes a direct relation of IOP to episcleral venous pressure. Normal episcleral venous pressure is between 9 and 10 mmHg. Increases in episcleral venous pressure lead to increases in

Figure 10.37 Resolving suprachoroidal hemorrhage following trabeculectomy in patient with Sturge–Weber syndrome

Although prophylactic partial-thickness scleral windows with full-thickness sclerostomies were performed, a large hemorrhage still occurred.

Figure 10.38 Dilated and tortuous episcleral vessels. A patient with carotid-cavernous fistula and increased intraocular pressure. These patients are also at risk for ocular ischemia leading to neovascular glaucoma, uveal effusions with angle closure, and central retinal arterial and venous obstruction.

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INTRODUCTION

The angle-closure glaucomas are a diverse group of disorders characterized by apposition of the iris to the trabecular meshwork. This results in mechanical blockage of aqueous outflow, progressive trabecular dysfunction, synechial closure and elevated intraocular pressure (IOP) that leads to optic nerve damage and loss of visual function.

Angle closure can be caused by one or a combination of the following: (1) abnormalities in the relative sizes or positions of anterior segment structures;

(2) abnormalities in the absolute sizes or positions of anterior segment structures; and (3) abnormal forces in the posterior segment which alter the anatomy of the anterior segment. Classification of angle closure by the anatomic level of the cause of the block, defined by the structure producing the ‘forces’ leading to the block, facilitates understanding of the various mechanisms, and appropriate treatment in any particular case becomes an exercise in deductive logic. We have defined four levels of block, from anterior to posterior. Each level of block may have a component of each of the levels preceding it. The appropriate treatment becomes more complex for each level of block, as each level may also require the treatments for lower levels of block.

With high-frequency, high-resolution, anterior segment ultrasound biomicroscopy (UBM), we can image the structures surrounding the posterior chamber, examination of which has been previously limited to histopathological examination. UBM is ideally suited to the study of the angle-closure glaucomas because of its ability to simultaneously image the ciliary body, posterior chamber, iris–lens relationship and angle structures. The currently available commercial unit operates at 50 MHz and provides lateral and axial resolution of approximately 50 m

and 25 m, respectively. Tissue penetration is approximately 4–5 mm. The scanner produces a 5 5-mm field with 256 vertical image lines (or A-scans) at a scan rate of 8 frames per second. The images shown in this chapter were obtained with the standard 50-MHz transducer.

In this chapter, we evaluate the angle-closure glaucomas with an emphasis on their anatomic basis.

BLOCK ORIGINATING AT THE LEVEL OF THE IRIS

Figure 11.1 Relative pupillary block. Relative pupillary block is the underlying mechanism in approximately 90% of patients with angle closure. Relative pupillary block typically occurs in hyperopic eyes, which have a shorter than average axial length, a more shallow anterior chamber, a thicker lens, a more anterior lens position, and a smaller radius of corneal curvature. In pupillary block, flow of aqueous from the posterior to the anterior chamber is impeded between the anterior surface of the lens and the posterior surface of the iris. Aqueous pressure in the posterior chamber becomes higher than that in the anterior chamber, causing anterior iris bowing, narrowing of the angle, and acute or chronic angle-closure glaucoma.

Figure 11.2 Relative pupillary block and angle closure (pupillary block–angle closure), UBM. In phakic pupillary block– angle closure, the iris has a convex configuration (white arrows) because of the relative pressure differential between the posterior chamber (PC) (the site of aqueous production) and the anterior chamber (AC). The cornea (C), anterior lens capsule (LC), and ciliary body (CB) are visible.

Figure 11.3 Pseudophakic pupillary block, UBM. In pseudophakic pupillary block, resistance to aqueous flow occurs because of posterior synechiae between the iris (I) and posterior chamber intraocular lens (PCIOL) which limit aqueous flow into the anterior chamber causing the iris in this patient to assume a bombé configuration. The angle is closed.

Figure 11.4 Iridovitreal block, UBM. Occasionally, aqueous access to the anterior chamber can be impeded by vitreous in the posterior or anterior chambers. In this illustration, the round bulge of vitreous prolapse into the anterior chamber is visible and the iris is convex. A posterior chamber intraocular lens is present.

Figure 11.5 Indentation gonioscopy. Indentation gonioscopy is critical to accurate diagnosis of the angle-closure glaucomas. During indentation, the central corneal curvature is altered, forcing aqueous posteriorly. The iris is pushed against the lens, creating a flap valve effect, which prevents aqueous from moving through the pupil into the posterior chamber. Aqueous is then forced into the angle recess, which opens an appositionally closed angle.

Figure 11.6 Indentation gonioscopy in relative pupillary block. In pupillary block, the peripheral iris is held in its anterior position because of the force of the aqueous behind it (top) (see also Figure 11.1). During indentation, the peripheral iris can move posteriorly because of the minimal resistance of the aqueous behind the iris plane to the force of indentation (bottom). This is very different from other forms of angle closure, such as plateau iris syndrome. (Reprinted from Ritch R, Liebmann JM. Argon laser peripheral iridoplasty. Ophth Surg Lasers 1996; 27: 289–300 (Figure 2).)

Figure 11.8 Synechiae formation, UBM. Iris apposition to the trabecular meshwork is an indication for laser iridotomy. In this patient, the iris is in contact with the trabecular meshwork. A small, clear, fluid-filled space is present immediately posterior to the region of iridotrabecular contact, indicating that the first location for appositional closure in this eye was in the midor upper trabecular meshwork.

Figure 11.7 Iris–lens contact in pupillary block, UBM. The anatomy of relative pupillary block in a phakic, unoperated patient is illustrated in this ultrasound biomicrograph. Scleral spur is clearly visible, and the trabecular meshwork just anterior to it is in contact with the iris. Note the relatively short region of iris–lens contact. Although there is resistance to flow through the pupillary space, the increased pressure within the posterior chamber compared to the anterior chamber has lifted the remaining iris off the lens surface.

Figure 11.9 Laser iridotomy, UBM. Laser iridotomy is the definitive treatment for pupillary block, and allows aqueous pressures in the anterior and posterior chambers to equalize and the iris to assume a planar configuration. Following laser iridotomy in the patient shown in Figure 11.8, the iris has flattened and the angle has opened. There are no peripheral anterior synechiae present.