Map-dot-fingerprint dystrophy, Cogan microcystic epithelial dystrophy, anterior basement membrane dystrophy
Table 7-3 Genetics of the Major Corneal Dystrophies
Most cases are sporadic; however, category 1 in rare cases
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)
Epithelial basement membrane dystrophy occurs in 6%–18% of the population, more commonly in women, with increasing frequency in patients older than 50 years. Gray patches, pseudocysts, and/or fine lines in the corneal epithelium are noted on examination and are best seen by using a broad oblique slit-lamp beam or with retroillumination. (See Chapter 2 for a discussion of slit-lamp biomicroscopy.) The clinician can also identify EBMD by using the sclerotic scatter illumination technique or by using the slit lamp with a cobalt-blue filter after instilling fluorescein. Four kinds of patterns are seen:
bleb pattern (Bron)
These abnormalities occur in varying combinations and can change in number and distribution over time. Fingerprint lines are thin, relucent, parallel, hairlike lines; several of them can be arranged in a concentric pattern so that they resemble fingerprints or a horse’s tail. Maps are geographic, irregular coastlines or islands of thickened, gray, hazy epithelium with scalloped, circumscribed borders (Fig 7-1). Dots are irregular round, oval, or comma-shaped intraepithelial opacities containing the debris of epithelial cells that collapsed and degenerated before reaching the epithelial surface (Fig 7-2). The bleb pattern (Bron) resembles pebbled glass and is best seen with retroillumination. The gray-white dots have discrete edges.
Figure 7-1 Epithelial basement membrane dystrophy (EBMD), seen using sclerotic scatter, demonstrates characteristic geographic maps.
(Courtesy of Robert S. Feder, MD.)
Figure 7-2 EBMD (seen using a broad, oblique slit beam) demonstrates geographic map areas and putty-gray opacities.
(Courtesy of Robert S. Feder, MD.)
Symptoms are typically related to recurrent epithelial erosions and/or blurred vision, ghosting, or monocular diplopia, and while more common in patients older than 30 years, they can occur at any age. The impact of EBMD on vision correlates with the degree of surface disruption and induced irregular astigmatism, which can be detected on keratometry or corneal topography. Symptoms of recurrent erosions typically occur in the morning; however, discomfort in the morning may also occur in patients with nighttime lagophthalmos and meibomian gland dysfunction. Punctate erosions are often noted in the inferior cornea in these settings. It is estimated that only 10% of patients with EBMD will have corneal erosions but that 50% of patients with recurrent epithelial erosions have evidence of this anterior dystrophy. Both eyes must be examined because evidence of the dystrophy may be found in the uninvolved eye. Unilateral dystrophic changes may be related to focal trauma rather than a dystrophy. In some cases, clinical findings may mimic corneal intraepithelial dysplasia; therefore, consideration should be given to submitting removed material for histologic study.
Asymptomatic patients may not require treatment. For patients with reduced acuity due to irregular astigmatism, epithelial debridement may be helpful. See Chapter 4 for a more complete discussion of recurrent erosions.