Congenital Anomalies

Choristoma

Epibulbar dermoids and episcleral osseous choristoma are discussed in Chapters 5 and 6.

Nanophthalmos

Nanophthalmos is a rare developmental disorder characterized by an eye with short axial length (15– 20 mm), a normal or slightly enlarged lens, thickened sclera, and a predisposition to uveal effusion and glaucoma. The condition is usually bilateral.

In studies, the thick and nonelastic sclera in nanophthalmos was found to demonstrate fraying and splitting of the collagen fibrils and abnormalities in the glycosaminoglycan matrix. These scleral changes may predispose the nanophthalmic eye to uveal effusion due to reduced protein permeability and impaired venous outflow through the vortex veins.

Glaucoma in nanophthalmic eyes may be caused by a variety of mechanisms, including angle closure, pupillary block, and open angle with elevated episcleral venous pressure.

Stewart DH III, Streeten BW, Brockhurst RJ, Anderson DR, Hirose T, Gass DM. Abnormal scleral collagen in nanophthalmos. An ultrastructural study. Arch Ophthalmol. 1991;109(7): 1017–1025.

Inflammations

See BCSC Section 8, External Disease and Cornea, for additional discussion of episcleritis and scleritis.

Episcleritis

Simple episcleritis is a self-limited, frequently recurrent condition that most commonly presents in the third to fifth decades as a slightly tender, movable, sectorial red area involving the anterior episclera. It affects males and females equally. There is usually no association with antecedent injury or systemic illness. Histologic examination shows vascular congestion; stromal edema; and a chronic nongranulomatous perivascular inflammatory infiltrate, composed primarily of lymphocytes (Fig 8- 3).

In contrast to simple episcleritis, nodular episcleritis more often affects females and those with systemic illness, such as rheumatoid arthritis. It is characterized by tender, elevated, pink-red nodules on the anterior episclera. Histologically, the nodules are composed of necrobiotic granulomatous inflammatory infiltrate, a palisading arrangement of epithelioid histiocytes around a central core of necrotic collagen. This light microscopic pattern is the same as that seen in rheumatoid nodules in subcutaneous tissue.

Figure 8-3 Simple episcleritis. Episcleral biopsy specimen from a patient with simple episcleritis demonstrates chronic nongranulomatous inflammatory infiltrate. (Courtesy of George J. Harocopos, MD.)

Scleritis

Scleritis is a painful, often progressive ocular disease with potentially serious sequelae. There is a high association with systemic autoimmune vasculitic connective tissue diseases.

Histologic examination of scleritis reveals 2 main categories: necrotizing and nonnecrotizing inflammation. Either type may occur anteriorly or posteriorly. Necrotizing scleritis may be nodular or diffuse, so-called brawny scleritis (Figs 8-4, 8-5). Both patterns demonstrate a palisading arrangement of epithelioid histiocytes and multinucleated giant cells surrounding sequestered areas of necrotic collagen (necrobiotic granuloma) (Fig 8-6). Peripheral to the histiocytes is a rim of lymphocytes and plasma cells. Multiple foci may show different stages of evolution. In the course of healing, the necrotic stroma is resorbed, leaving in its wake a thinned scleral remnant prone to staphyloma formation (Fig 8-7). Severe ectasia of the scleral shell predisposes to herniation of uveal

tissue through the defect, a condition known as scleromalacia perforans.

Nonnecrotizing scleritis is characterized by a perivascular lymphocytic and plasmacytic infiltrate without a granulomatous inflammatory component. Vasculitis may be present in the form of fibrinoid necrosis of vessel walls.

Dubord PJ, Chambers A. Scleritis and episcleritis: diagnosis and management. Focal Points: Clinical Modules for Ophthalmologists. San Francisco: American Academy of Ophthalmology; 1995, module 9.

Figure 8-4 This patient has a sectoral nodular anterior scleritis that causes severe ocular pain and photophobia. (Courtesy of

Harry H. Brown, MD.)