Corneal dystrophies are a group of genetically determined, progressive disorders that affect the layers of the cornea. They are usually inherited and affect both eyes equally. Epithelial basement membrane dystrophy is a rare, non-progressive abnormality of the corneal epithelium caused by mutations in genes encoding corneal epithelial keratins. It is characterized by irregular thickening of the epithelial basement membrane and intraepithelial cysts. Reis-Bucklers corneal dystrophy is an autosomal dominant disorder characterized by replacement of the Bowman layer by connective tissue bands, causing severe recurrent erosions in childhood and potential visual impairment. Honeycomb corneal dystrophy is a less severe form of Reis-Bucklers, appearing as

1. Othman Al-Abbadi, M.D

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

3.  Epithelial
 Bowman layer
 Stromal
 Endothelial

4. 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

6. 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.

8. Onset
2nd
decade
10% of pts develop recurrent corneal erosions in 3rd
decade & others remain asymptomatic throughout life.

9. 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

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

15. Inheritance
Autosomal dominant
Histology-
Irregular thickening of the epithelial basement
membrane & intraepithelial cysts

16. 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

23.  Known as corneal basement dystrophy type I (CBD1).
Inheritance
Autosomal dominant

24. Histology
Replacement of the Bowman layer by connective tissue
bands.
Symptoms
Severe recurrent corneal erosions in childhood.
Visual impairment may occur

25. 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.

28.  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.

29. Termed honeycomb-shaped corneal dystrophy and
corneal basement dystrophy type II (CBD2)
Less severe than Reis-Buckler
Inheritance
Autosomal dominant

30. Histology
curly fibers in Bowman layer on electron microscopy
Signs
subepithelial opacities in a honeycomb morphology involving
central cornea
less indovodually defined subepithelial opacities than CBD1
Treatment not required as visual impairment is less than Reiss-
Bucklers dystrophy