PATHOLOGY

EBMD is an abnormality of epithelial turnover, maturation, and production of basement membrane. Histologic findings include the following:

• sheets of intraepithelial, multilamellar basal lamina material (maps)

• intraepithelial extension of basal laminar material (fingerprint lines)

• intraepithelial pseudocysts containing cytoplasmic debris (dots)

• irregular, subepithelial accumulation of fibrogranular material (bleb)

PATHOLOGY

Intraepithelial cysts consisting of degenerated epithelial cell products (cellular debris that is periodic acid–Schiff [PAS] positive and fluoresces) are present. The epithelial cells contain an electron-dense accumulation of fibrogranular material surrounded by tangles of cytoplasmic filaments (“peculiar substance”). There are frequent mitoses and a thickened basement membrane with projections into the basal epithelium; the basal epithelial cells have increased levels of glycogen. On confocal microscopy, hyporeflective areas ranging from 40 to 150 μm in diameter are seen in the basal epithelium and contain potential reflective spots.

CLINICAL PRESENTATION

Meesmann corneal dystrophy appears very early in life. Tiny intraepithelial vesicles are seen—most easily with retroillumination—extending to the limbus. These appear as minute bubblelike blebs (Fig 7-3). In 85% of eyes, the entire epithelium is affected. The epithelium surrounding the cyst is clear. Whorled and wedge-shaped epithelial patterns may be seen. The cornea may be slightly thinned, and corneal sensation may be reduced. Symptoms are usually limited to mild ocular irritation and a slight decrease in vision. Some patients report glare and light sensitivity. Painful recurrent erosions may occur.

The Stocker-Holt variant, which maps to a different gene (see Table 7-3), may have an earlier onset and demonstrate more severe signs and symptoms.

MANAGEMENT

Most patients require no treatment, but soft contact lens wear may be helpful if symptoms are frequent.

Figure 7-3 A, Meesmann corneal dystrophy, appearing as tiny bubblelike blebs with indirect slit-lamp illumination. B, Blebs are also well seen against the red reflex.

(Part A courtesy of Robert S. Feder, MD; part B courtesy of Richard Abbott, MD.)

Figure 7-4 Lisch epithelial corneal dystrophy, characterized by bands of feathery, gray opacities. Retroillumination shows sectorial, densely crowded, clear microcysts in a feathery shape.

(Courtesy of Robert W. Weisenthal, MD.)

PATHOLOGY

Diffuse cytoplasmic vacuolization of affected cells, which are PAS positive, is seen in light and transmission electron microscopy. On immunohistochemistry, there is scattered staining on Ki67 without evidence of increased mitotic activity. Confocal microscopy shows highly reflective cytoplasm and hyporeflective nuclei.

CLINICAL PRESENTATION

On direct slit-lamp examination, discrete sectorial, band-shaped and feathery gray lesions are seen in whorled, flame-shaped, or feathery patterns. Retroillumination reveals intraepithelial, densely crowded, clear microcysts (Fig 7-4). The surrounding epithelium is clear. In Meesmann dystrophy, such band-shaped, feathery lesions do not exist, and the corneal involvement is more diffuse. Also, the intraepithelial cysts of Meesmann dystrophy are not as densely crowded as in Lisch dystrophy but are isolated, with clear spaces between the cysts.

MANAGEMENT

Patients with Lisch dystrophy are pain free. There may be an associated decrease in vision. Corneal debridement may be attempted but often results in recurrence. Contact lenses may be helpful for more severe cases. There is one case report on the successful treatment of Lisch dystrophy (one eye) using photorefractive keratectomy (PRK) with mitomycin.

Alvarez-Fischer M, de Toledo JA, Barraquer RI. Lisch corneal dystrophy. Cornea. 2005;24(4): 494–495.

Lisch W, Büttner A, Oeffner F, et al. Lisch corneal dystrophy is genetically distinct from Meesmann corneal dystrophy and maps to xp22.3. Am J Ophthalmol. 2000;130(4): 461–468.

Wessel MM, Sarkar JS, Jakobiec FA, et al. Treatment of Lisch corneal dystrophy with photo-refractive keratectomy and mitomycin C. Cornea. 2011;30(4):481–485.

PATHOLOGY

Light microscopy shows subepithelial and stromal amyloid deposits. Disruption of epithelial tight junctions leads to abnormally high epithelial permeability. Confocal microscopy shows irregular, elongated epithelial cells with large accumulations of brightly reflective material noted within or beneath the epithelium and within the anterior stroma. Amyloid deposition is noted in the basal epithelial layer on transmission electron microscopy. See also Chapter 8 for a more complete discussion of amyloidosis.

CLINICAL PRESENTATION

Onset occurs in the first to second decade of life with groups of multiple small nodules (mulberry configuration) or with subepithelial lesions that may appear similar to those of band keratopathy (Fig 7-5A, B). The lesions are visible on fluorescein staining. There is a significant decrease in vision, with photophobia, irritation, and tearing, as well as progression of protruding subepithelial lesions. Superficial vascularization is often seen. Stromal opacification or larger nodular lesions (kumquat-like lesions) may develop (Fig 7-5C).

MANAGEMENT

The lesions recur within a few years following superficial keratectomy, lamellar keratoplasty (LK), or penetrating keratoplasty (PK). Soft contact lenses are effective in reducing the abnormal epithelial permeability in an effort to decrease recurrence.

Ide T, Nishida K, Maeda N, et al. A spectrum of clinical manifestations of gelatinous drop-like corneal dystrophy in Japan. Am J Ophthalmol. 2004;137(6):1081–1084.

Figure 7-5 Gelatinous droplike corneal dystrophy. A, Mulberry type. B, Band keratopathy type. C, Kumquat-like type.

(Reproduced with permission from Weiss JS, Møller HU, Aldave AJ, et al. IC3D classification of corneal dystrophies—edition 2. Cornea. 2015;34(2):130).

Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.