Othman Al-Abbadi, M.D

Corneal dystrophies are group of progressive, usually bilateral, mostly genetically determined, non-inflammatory opacifying disorders.

Epithelial Bowman layer Stromal Endothelial

Corneal dystrophies They are usually inherited. They affect the right and left eyes equally. They are not caused by other factors, such as injury

or diet. Most progress gradually. Usually begin in one of the five corneal layers and

may later spread to nearby layers. Most do not affect other parts of the body, nor are

they related to diseases affecting other parts of the eye or body.

Most can occur in healthy individual

Inheritance- sporadic & rarely Autosomal dominant

Histology- thickening of basement membrane with deposition of fibrillary protein between basement membrane & bowman’s layer. Absence of hemidesmosomes of basal epithelial cells which is responsible for recurrent corneal erosions.

Onset

2nd decade10% of pts develop recurrent corneal erosions in 3 rd decade & others remain asymptomatic throughout life.

Signs-Lesions are often best visualized by retroillumination or scleral scatter.

Over time pattern and distribution varies; they may be absent or subtle in a fellow eye.

Dot-like and microcystic epithelial lesions* Subepithelial map-like patterns surrounded by a faint

haze* Whorled fingerprint-like lines. Bleb-like subepithelial pebbled glass pattern

Rare, non-progressive abnormality of corneal epithelial metabolism, underlying which mutations in the gene encoding corneal epithelial keratins have been reported.

Inheritance Autosomal dominant

Histology- Irregular thickening of the epithelial basement membrane & intraepithelial cysts

Symptoms Asymptomatic, or there may be recurrent erosions and blurring (usually mild).

Signs A lot of tiny intraepithelial cysts of uniform size but

variable density are maximal centrally & extend towards but do not reach the limbus

Thinning & hyposthesia of the cornea

Known as corneal basement dystrophy type I (CBD1).

InheritanceAutosomal dominant

HistologyReplacement of the Bowman layer by connective tissue bands.

SymptomsSevere recurrent corneal erosions in childhood. Visual impairment may occur

Signs Grey–white geographic subepithelial opacities, most

dense centrally, increasing in density with age to form a reticular pattern.

Corneal sensation is reduced. Histopathology, including electron microscopy, may be

required for definitive distinction from Thiel–Behnke dystrophy in some cases.

Corneal sensation is reduced & visual impairment may occur due to scarring at level of Bowman layer.

Treatment is directed at recurrent erosions. Excimer laser Keratectomy achieves satisfactory control in some patients.

Termed honeycomb-shaped corneal dystrophy and corneal basement dystrophy type II (CBD2)

Less severe than Reis-Buckler

Inheritance Autosomal dominant

Histology curly fibers in Bowman layer on electron microscopy

Signs subepithelial opacities in a honeycomb morphology involving central cornealess indovodually defined subepithelial opacities than CBD1

Treatment not required as visual impairment is less than Reiss- Bucklers dystrophy