Map-dot-fingerprint dystrophy occurs when the epithelium's basement membrane (the foundation on which epithelial cells anchor and organize themselves) develops abnormally. It usually affects adults between the ages of 40 and 70, although it can develop earlier in life.
The affected epithelium will have a map-like appearance on slit-lamp examination, i.e., large, slightly gray outlines that look like a continent on a map. In addition, clusters of opaque dots may be present. Less frequently, the irregular basement membrane will form concentric lines in the central cornea that resemble small fingerprints. Due to the abnormal basement membrane, the epithelial cells cannot properly adhere to it. This, in turn, may cause recurrent epithelial erosion, where the epithelium's outermost layer rises slightly, creating a small gap.
Secondary epithelial erosions can be a chronic problem, causing periodic blurred vision. They may also expose the nerve endings that line the tissue resulting in moderate to severe pain lasting as long as several days. Generally, the pain will be worse on awakening in the morning. Other symptoms include sensitivity to light, excessive tearing, and foreign body sensation in the eye. Symptoms typically “flare up” occasionally and resolve on their own with no lasting loss of vision.
If treatment is needed, epithelial erosions are primarily treated with lubricating eye drops and ointments. Erosions usually heal within three days, although periodic flare-ups may occur for several weeks thereafter. Additional treatment for recurrent cases include anterior corneal stromal punctures to allow better adherence of cells; corneal scraping, and the use of the excimer laser to remove surface irregularities, called phototherapeutic keratectomy (PTK).