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 Encyclopedia - Corneal Dystrophy

What are the symptoms of epithelial basement membrane dystrophy?
How is epithelial basement membrane dystrophy treated?
What are the symptoms and causes of corneal endothelial cell dystrophy?
How is corneal endothelial cell dystrophy treated?

Corneal dystrophy is the gradual deterioration of one layer or another of the cornea, the transparent outer layer of the eye through which light enters (See Anatomy of the Eye). The cornea comprises five layers of tissue. Starting from the outside, the layers are the surface epithelium, its basement membrane, the stroma (the thickest layer, constituting 90 percent of the cornea), the internal endothelium, and its basement membrane. The endothelium acts to remove excess moisture, thus preventing abnormal swelling of the cornea.

There are a variety of corneal dystrophies. They can affect the epithelium, the stroma, or the endothelium. They often are inherited and can occur at an early age, even at birth. The two most common are epithelial basement membrane dystrophy and endothelial cell dystrophy.

What are the symptoms of epithelial basement membrane dystrophy?

Epithelial basement membrane dystrophy generally occurs in adults after the age of 40, and it can come as late as age 70. In this form of dystrophy, the basement membrane begins to become thick and irregular, so that the once-even layer of cells starts to buckle as the cells break apart and fall off the membrane. A magnified view of an affected membrane under a slit lamp will show an irregular pattern of cysts, ridges, and whirls. Ophthalmologists call the condition "map-dot-fingerprint dystrophy."

The breakdown of the basement membrane in epithelial cell dystrophy causes redness of the eye and discomfort that can range from moderate irritation to severe pain. Those symptoms generally are worse at the start of the day, because sleep does not permit the blinking that keeps the surface of the cornea lubricated with tears.

How is epithelial basement membrane dystrophy treated?

Treatment for corneal epithelial cell dystrophy usually starts with efforts to augment the natural lubrication, using artificial tears and saline solutions just before sleep and eye drops applied periodically during the day. The patient may be told to wear a customized eye patch or contact lens to achieve the necessary lubrication. Also, measures to keep the home environment more humid, using vaporizers or similar equipment, may be recommended. If these measures fail, surgery or laser therapy to remove unlubricated cells may be needed.

What are the symptoms and causes of corneal endothelial cell dystrophy?

Corneal endothelial cell dystrophy, also called Fuch's dystrophy, also is most common in adults in their 40s and 50s, affecting women more than men. It, too, tends to be hereditary, and it generally affects both eyes. Fuch's dystrophy occurs when the natural pumping activity of the endothelium begins to deteriorate. Excess fluid starts to accumulate, causing the cornea to become swollen and less transparent, so that visual ability can deteriorate with time.

The most noticeable symptom of corneal endothelial cell dystrophy is blurry vision, particularly evident at wake-up time because while the eyes are closed during the sleep, less fluid is able to evaporate. Vision improves as the day goes on, as more fluid evaporates.

How is corneal endothelial cell dystrophy treated?

To treat for endothelial cell dystrophy, steps are taken to remove moisture from the eyes, using different ointments and eye drops. But these measures often fail to stop the progression of the condition, so a corneal transplant may be needed, using tissue taken from the eyes of a donor. Tissue matching to prevent rejection of the transplanted tissue is not as important for a corneal transplant as for other organs. Because the cornea has very few blood vessels, it is less exposed to attack by the immune system. Corneal transplants were thus the first to be widely successful in human patients. A network of eye banks exists to obtain corneal tissue and match it for appropriate patients.

Cataract operations and other kinds of eye surgery can increase the risk and hasten the progression of endothelial cell dystrophy by causing edema, a buildup of fluid. Persons with a family history of this kind of corneal dystrophy are advised to tell their doctors when any such surgery is planned. They are also advised to undergo regular examinations to detect the condition at its earliest, most treatable stage.

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