A corneal dystrophy is a condition in which one or more parts of the cornea lose their normal clarity due to a buildup of material that clouds the cornea. These diseases:
Corneal dystrophies affect vision in different ways. Some cause severe visual impairment, while a few cause no vision problems and are only discovered during a routine eye exam. Other dystrophies may cause repeated episodes of pain without leading to permanent vision loss. Some of the most common corneal dystrophies include keratoconus, Fuchs’ dystrophy, lattice dystrophy, and map-dot-fingerprint dystrophy.
Kerataconus is a progressive thinning of the cornea. It is the most common corneal dystrophy in the U.S., affecting one in every 2,000 Americans. It is most prevalent in teenagers and adults in their 20s.
Keratoconus causes the middle of the cornea to thin, bulge outward, and form a rounded cone shape. This abnormal curvature of the cornea can cause double or blurred vision, nearsightedness, astigmatism, and increased sensitivity to light.
The causes of keratoconus aren’t known, but research indicates it is most likely caused by a combination of genetic susceptibility along with environmental and hormonal influences. About 7 percent of those with the condition have a history of kerataconus in their family. Keratoconus is diagnosed with a slit-lamp exam. Your eye care professional will also measure the curvature of your cornea.
Keratoconus usually affects both eyes. At first, the condition is corrected with glasses or soft contact lenses. As the disease progresses, you may need specially fitted contact lenses to correct the distortion of the cornea and provide better vision.
In most cases, the cornea stabilizes after a few years without causing severe vision problems. A small number of people with keratoconus may develop severe corneal scarring or become unable to tolerate a contact lens. For these people, a corneal transplant may become necessary.
Fuchs’ dystrophy is a slowly progressing disease that usually affects both eyes and is slightly more common in women than in men. It can cause your vision to gradually worsen over many years, but most people with Fuchs’ dystrophy won’t notice vision problems until they reach their 50s or 60s.
Fuchs’ dystrophy is caused by the gradual deterioration of cells in the corneal endothelium; the causes aren’t well understood. Normally, these endothelial cells maintain a healthy balance of fluids within the cornea. Healthy endothelial cells prevent the cornea from swelling and keep the cornea clear. In Fuchs’ dystrophy, the endothelial cells slowly die off and cause fluid buildup and swelling within the cornea. The cornea thickens and vision becomes blurred.
As the disease progresses, Fuchs’ dystrophy symptoms usually affect both eyes and include:
- Glare, which affects vision in low light
- Blurred vision that occurs in the morning after waking and gradually improves during the day
- Distorted vision, sensitivity to light, difficulty seeing at night, and seeing halos around light at night
- Painful, tiny blisters on the surface of the cornea
- A cloudy or hazy looking cornea
The first step in treating Fuchs’ dystrophy is to reduce the swelling with drops, ointments, or soft contact lenses. If you have severe disease, your eye care professional may suggest a corneal transplant.
Lattice dystrophy gets its name from a characteristic lattice-like pattern of deposits in the stroma layer of the cornea. The deposits are made of amyloid, an abnormal protein fiber. Over time, the deposits increase and the lattice lines grow opaque, take over more of the stroma, and gradually converge to impair vision.
Although lattice dystrophy can occur at any time in life, it most commonly begins in childhood between the ages of 2 and 7. In some people, amyloid deposits can accumulate under the epithelium of the cornea. This can erode the epithelium, and cause a condition known as recurrent epithelial erosion. This erosion alters the cornea’s normal curvature and causes temporary vision problems. It can also expose the nerves that line the cornea and cause severe pain.
To ease this pain, an eye care professional may prescribe eye drops and ointments to reduce the friction of the eyelid against the cornea. In some cases, an eye patch may be used to immobilize the eyelid. The erosions usually heal within days, although you may have some pain for the next six to eight weeks.
By age 40, some people with lattice dystrophy have scarring under the epithelium that can impact vision to such an extent that the most effective treatment will be a corneal transplant. Although the early results of corneal transplantation are typically good, lattice dystrophy may reappear later and require long-term treatment.
Map-Dot-Fingerprint dystrophy, also known as epithelial basement membrane dystrophy, occurs when the basement membrane develops abnormally and forms folds in the tissue. The folds create gray shapes that look like continents on a map. There also may be clusters of opaque dots underneath or close to the maplike patches. Less frequently, the folds form concentric lines in the central cornea that resemble small fingerprints.
Symptoms include blurred vision, pain in the morning that lessens during the day, sensitivity to light, excessive tearing, and a feeling that there’s something in the eye.
Map-dot-fingerprint dystrophy usually occurs in both eyes and affects adults between the ages of 40 and 70, although it can develop earlier in life. Typically, map-dot-fingerprint dystrophy will flare up now and then over the course of several years and then go away, without vision loss. Some people can have map-dot-fingerprint dystrophy but not experience any symptoms.
Others with the disease will develop recurring epithelial erosions, in which the epithelium’s outermost layer rises slightly, exposing a small gap between the outermost layer and the rest of the cornea. These erosions alter the cornea’s normal curvature and cause blurred vision. They may also expose the nerve endings that line the tissue, resulting in moderate to severe pain over several days.
The discomfort of epithelial erosions can be managed with topical lubricating eye drops and ointments. If drops or ointments don’t relieve the pain and discomfort, there are outpatient surgeries including:
- Anterior corneal puncture, which help the cells adhere better to the tissue
- Corneal scraping to remove eroded areas of the cornea and allow healthy tissue to regrow
- Laser surgery to remove surface irregularities on the cornea