One of three types of corneal dystrophy, macular dystrophy is the least common and the most severe. It is an autosomal recessive genetic disorder characterized by non-inflammatory clouding of the cornea that causes decreased visual acuity.
Causes of Macular Dystrophy
The gene responsible for this corneal disorder is located on chromosome 6 and appears to be involved in the synthesis of keratan sulfate. Type 1 macular dystrophy is characterized by an absence of keratan sulfate, whereas the mucopolysaccharide is present in type 2. Keratan sulfate is also found in cartilage.
There are other types of macular dystrophy in which the central portion of the retina is affected by degeneration, called vitelliform macular dystrophy. This is also an inherited disorder with both juvenile and adult onset subtypes.
Symptoms and Diagnosis of Macular Dystrophy of the Cornea
The disorder is usually apparent in the first decade of life. Photosensitivity eventually develops as the cornea thins in the center and vision loss progresses with adulthood. The person often suffers from eye pain and the sensation of the a foreign body in the eye. Glycosaminoglycan deposits can be detected by a pathologist who stains a corneal biopsy with colloidal iron and Alcian blue. The entire thickness of the cornea is usually involved with stromal opacities that extend into the peripheral cornea. The opacities can often be seen under a light microscope.
A corneal biopsy is rarely pursued by ophthalmologists for diagnosis of eye disorders, but when it is done, the surgical technique involves taking a sample of the clear outer eye. They try to avoid the central axis as it may interfere with vision, and is performed while awake. If a full thickness biopsy is taken, a temporary patch may need to be worn afterwards.
Treatment of Macular Dystrophy of the Cornea
Corneal erosions are treated by covering with a patch contact lens and possibly antibiotics. An antibiotic patch may also be used. To prevent corneal lesions, lubricating drops such as artificial tears (0.9% saline) may be suggested.
Hypertonic saline (5% sodium chloride) may be suggested to help the stroma adhere to the epithelium. Laser therapy called phototherapeutic keratectomy may be pursued to remove superficial opacities. Sunglasses can help with photosensitivity and glare.
Corneal transplantation is a common option, though the corneal dystrophy may recur with time.
References
eMedicine from WebMD (accessed July 19, 2010)
Demers, Corneal biopsy. Techniques in Ophthalmology, June 2003.
WrongDiagnosis, Macular dystrophy corneal type 1 (accessed July 19, 2010)
Alicia Mae Prater - Alicia received her doctorate in Experimental Pathology in 2007. She has been a freelance writer and scientific editor since 2008.
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