Excerpt from Dystrophy, Macular

Synonyms, Key Words, and Related Terms: corneal dystrophy, corneal stroma, anterior corneal dystrophy, stromal corneal dystrophy, posterior corneal dystrophy, corneal dystrophies

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Background: Macular dystrophy is an autosomal recessive condition, which is the least common but the most severe of the 3 major stromal corneal dystrophies. It is characterized by multiple, gray-white opacities that are present in the corneal stroma and that extend out into the peripheral cornea.

Pathophysiology: The cornea is the clear outer coat of the front of the eye. A dystrophy of the cornea is defined as a bilateral noninflammatory clouding of the cornea. Corneal dystrophies can be placed into 3 categories based on their location within the cornea. Anterior corneal dystrophies affect the corneal epithelium and may involve the Bowman membrane. Stromal corneal dystrophies (which include macular dystrophy) affect the central layer of the cornea, the stroma. Posterior corneal dystrophies involve the Descemet membrane and the endothelium.

Most corneal dystrophies have an onset prior to 20 years; exceptions include map-dot-fingerprint dystrophy and Fuchs corneal dystrophy. Most corneal dystrophies are dominantly inherited; exceptions are macular dystrophy, type 3 lattice dystrophy, and the autosomal-recessive form of congenital hereditary endothelial dystrophy.

Subgroups of macular dystrophy can be identified by immunohistochemical methods. Keratan sulfate was not detected in the serum of patients with histopathologically confirmed macular corneal dystrophy. Since keratan sulfate in the serum appears to be derived predominantly from the normal turnover of cartilage, these studies strongly suggest that the defect in keratan sulfate synthesis in macular corneal dystrophy is not restricted to corneal cells and that this condition is one manifestation of a systemic disorder of keratan sulfate.

Frequency:

In the US: Uncommon

Mortality/Morbidity:

Corneal changes become visible in the first decade of life; a significant reduction in vision usually occurs by age 20-40 years.

Eye pain from recurrent corneal erosions can occur but is much less common than in patients with lattice or granular dystrophies.

Sex: No sexual predilection has been reported.

Age: Corneal changes become visible in the first decade of life; vision may be significantly reduced by age 20-40 years.