Dystrophies. Molecular Causes. Anterior Membrane Dystrophies (epithelium, basement membrane and Bowman s layer)

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1 Dystrophies Characteristics of corneal dystrophies About half the members of appropriate age to have the dystrophy( usually autosomal dominant): inherited Usually seen in the first or second decade of life Roughly equal sex distribution (except Fuchs dystrophy) Bilateral, symmetric, central, avascular, and often progressive Wide variation in severity, unrelated to other local or systemic diseases, some may actually be degenerative Classified by anatomic layer (primarily one), morphological characteristics, person s name, and specific histopathologic and histochemical characteristics of deposited material Molecular Causes In recent years, linkage studies have led to the identification of genes responsible for several of these corneal dystrophies Molecular biology has given new insights into the pathogenesis Future classification may be genotypic Anterior Membrane Dystrophies (epithelium, basement membrane and Bowman s layer) Map-dot-fingerprint dystrophy (EBMD) : most common anterior dystrophy Names: Cogan s microcystic: map, fingerprint, dot like dystrophy, non traumatic recurrent erosion, most common, F>M Slit lamp: maps (irregular, geographic appearance), dots (putty-like), microcysts, fingerprints, nets and erosions, negative staining, best observed using retroillumination All types tend to come and go spontaneously and move to different portions of the cornea, manifest one or all 3 1

2 Pathologic changes consist of thickening of the BM with extensions into the epithelium in map, intraepthelial cysts and debris in dots, multiplication and thickening of BM in fingerprint, absence of hemidesmosomes Subjective symptoms: often asymptomatic, but painful foreign body sensation due to erosions (10%), visual acuity somewhat reduced if lesions clustered in pupillary zone, also irregular astigmatism Etiology: nonhereditary disease (in age group) or autosomal dominant inheritance with variable penetrance (signs as early as 10 yrs) Treatment: REE management, hypertonic, topical lubricants and ointments, epithelial debridement, excimer Dystrophy vs degeneration (especially in older pts) 2

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4 Meesman s Juvenile Dystrophy (Stocker-Holt) Etiology: Rare, inherited autosomal dominant trait, bilateral, symmetrical, appears in first few months of life, not symptomatic until 3-4 th decade Slit lamp: multiple, small gray-white punctate opacities (cysts or vesicles) in the intrapalpebral zone, with clear epithelium in between, regular in size and shape: bleblike, microcysts, (vesicles), lesions on retroillumination, gray round opacities on direct, maximal centrally Subjective symptoms: asymptomatic until middle age, then irregular astigmatism and intermittent irritation and photophobia when cyst rupture & staining occurs, vision often spared Treatment: Wearing soft contacts can reduce the number of cysts and the symptoms, superficial keratectomy if vision impaired 4

5 Reis-Bucklers Ring-shaped Etiology: rare, bilateral, symmetrical, autosomal dominant with high penetrance, central corneal opacity, appears in first few years of life, primary cause unknown Slit lamp: irregular epithelium with diffuse irregular, patchy, geographic, reticular, ring-like with honeycomb pattern grey-white opacities in the region of Bowman s layer, later central opacities appear in a reticulated pattern Subjective symptoms: around 5 yrs., recurrent erosions, conjunctival injection, and gradual opacification cause episodes of severe pain, injection, photophobia and ocular redness; by age of 30, erosions become infrequent but visual acuity quite affected by opacification, irregular astig., decreased corneal sensitivity Treatment: Erosion treatment, keratoplasty (lamellar or penetrating- high incidence of recurrence), superficial keratectomy, excimer (PTK)-often disappointing results due to refractive changes 5