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39 year old Hispanic woman with a ten year history of gradual blurring of vision in both eyes
Digital Journal of Ophthalmology 1997
Volume 3, Number 16
April 2, 1997
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David Huang, M.D., Ph.D. | Doheny Eye Institute, University of Southern California, Los Angeles, California
Peter J. McDonnell, M.D. | Doheny Eye Institute, University of Southern California, Los Angeles, California
Diagnosis and Discussion
Macular Corneal Dystrophy

Macular dystrophy is the least common of the 3 classic stromal dystrophies and the only one that has an autosomal recessive inheritance pattern (1). Macular dystrophy is a bilateral, symmetric disease that appears in the first decade of life and affects the central portion of the anterior layers of the stroma. Diffuse, grayish white spots with indistinct edges are seen. By the third decade, the diffuse stromal opacity with its ground glass appearance extends posteriorly to the endothelium and laterally to the limbus. Within it are small irregular, white patches that continue to expand, enlarge, and become more confluent. Late in the course of the disease, Descement's membrane becomes opacified and there are endothelial guttate changes. The epithelium remains smooth until the late stages of the disease, when the subepithelial opacities cause elevations and irregularities of the corneal surface. In the late stages, the vision is also reduced, and infrequently there are recurrent erosions and decreased corneal sensation.

There are two types of macular dystrophy distinguished by their biochemical characteristics. Type 1 is the more prevalent type. Antigenic keratan sulfate is missing FROM the cornea, serum, and cartilage due to a defect in the specific sulfotransferase involved in the sulfation of lactose-aminoglycans and abnormal unsulfated keratan-aminoglycan is produced. In type 2, dermatan sulfate chains are 40% shorter than normal and the synthesis of both keratan and dermatan sulfates are 30% below normal.

Histopathologically, the opacities are accumulations of glycosylaminoglycans (GAG) within the endoplasmic reticulum. They are thought to accumulate because of an inability to break down corneal keratan sulfate. The deposits stain with Alcian blue and colloidal iron.

The established treatment is penetrating keratoplasty. The disease can recur in the graft with the recurrence rate thought to be inversely proportional to the graft size (2). Excimer laser phototherapeutic keratectomy has been attempted, but post-treatment vision may still be clouded by residual diffuse stromal haze (3).