Introduction
Map-dot-fingerprint dystrophy is a problem of the most superficial layer of the cornea called the epithelium and can be acquired through trauma or as an inherited problem. The most common symptoms are intermittent, severe, painful episodes in the morning which resolve slowly over the day. This condition does not cause blindness but can reduce vision because of corneal swelling. Treatment attempts to keep the epithelium from tearing from one to six months, to allow the natural glue or basement membrane to regenerate.
Corneal Anatomy
The cornea is a clear cover over the surface of the eye that protects the inner workings of the eye from the outside world. The five basic layers of the cornea are the epithelium, Bowman’s layer, stroma, descemet’s membrane and endothelium. The top layer is called the epithelium and is analogous to the skin or the rest of the body. Just as the skin has many nerve fibers and is very sensitive to cuts and tears, the epithelium also has many nerve fibers and reacts painfully when it is disturbed. The epithelium is held in place by a natural glue called the basement membrane. The basement membrane is made by the epithelium itself and a normal epithelium glues itself securely to the rest of the cornea. When trauma occurs and the epithelium is scraped away, the basement membrane can also scraped away, resulting in a weak area of bonding between the epithelium and the rest of the cornea. This area can then easily tear by rubbing the eye or by the normal motion of the lids against the cornea.
Map-Dot-Fingerprint Dystrophy
Corneal abrasions or erosions are perhaps the most common problems for which patients see an ophthalmologist. Invariably, pain occurs with loss of the epithelium, and this severe pain prompts an immediate visit to the doctor. In most cases, the scratch that has removed a portion of the epithelium heals quickly with a patch or contact lens, and no further problems are encountered with respect to the original injury.
In some cases however, the injury is severe, or is produced in such a manner as to cause repeated corneal abrasions or a scratched cornea. In these cases, the basement membrane (the glue that holds the epithelium to the cornea) has been disrupted, and since this glue is secreted by the epithelium, the repeated abrasions prevent adequate amounts of basement membrane from forming, leading to a cycle of erosions followed by brief periods of relief.
In still other cases, no trauma can be identified prior to the appearance these symptoms and an abnormality of the basement membrane that is inherited is the cause of the problem. Such cases are not common but represent the most difficult patients in which to achieve a lasting remission of the disease. This disease can also follow various kinds of eye surgeries that utilize incisions of the cornea and surrounding areas. These cases can sometimes be resolved by modifying the original surgery.
The Examination
The history of map-dot-fingerprint dystrophy often makes the diagnosis clear. The patient usually complains of severe pain either in the early morning hours or upon waking, often reporting repeated doctor visits which revealed nothing. This occurs because the epithelium tends to heal very quickly. It often heals well enough by the time the patient is seen that nothing will be seen when the doctor examines the eye with a slit lamp microscope. Dry eyes can often be associated with this disease and treatment of these problems will sometimes cause a lasting remission of the problem.
Sometimes, if the cornea is examined in a special way that utilizes reflected light from inside the eye (called retroillumination), the features of map-dot-fingerprint dystrophy can be seen. The name describes what the doctor sees in the slit lamp microscope: the cornea appears to have small, elevated patches, dots or even lines that look something like fingerprints. Often similar findings will be present in the other eye if this is an inherited problem.
Treatment
Treatment revolves around an attempt to keep the epithelium in place long enough to allow it to heal permanently. This period of time varies but is somewhere between two and six months. For very mild cases, lubricants such as artificial tears and soothing ointments at night may be sufficient. In more severe cases, concentrated salt solutions may be used to reduce the swelling and prevent the eyelid from tearing it away from the cornea. In fact, simply opening the eyes very slowly the first time in the morning can sometimes prevent the epithelium, which has become swollen from closed lids and humidity during the sleeping hours, from tearing away. If these measures fail, a therapeutic contact lens can protect the epithelium. It can be worn continuously (except for cleaning or replacement) for several months to heal this problem.
Sometimes surgery a (subtotal epithelial keratectomy) is necessary to heal this problem. In these cases the epithelium is completely removed from the cornea and allowed to heal back in one sheet. This procedure has a success rate of approximately 60-70% and is performed only on patients who have not responded to other treatments. Another surgical procedure involves making tiny puncture marks in the affected area and allowing tiny scars to form which lie the epithelium down to the cornea. This procedure is less successful and leaves a scar on the cornea. However it can be helpful when the affected area does not lie in the center of vision.
