What Is a Corneal Dystrophy?
A corneal dystrophy is a condition in which one or more parts of the cornea lose their normal clarity because of a buildup of cloudy material. There are over 20 corneal dystrophies that affect all parts of the cornea.
Common Traits of Corneal Dystrophies
Corneal dystrophies share many things in common, including the following:
- They are usually inherited
- They affect the right and left eyes equally
- They are not caused by outside factors, such as injury or diet
- Most progress gradually (over time)
- Most usually begin in one of the five corneal layers and may later spread to nearby layers
- Most do not affect other parts of the body, nor are they related to diseases affecting other parts of the eye or body
- Most can occur in otherwise totally healthy people, male or female
Corneal dystrophies affect vision in different ways. Some cause severe visual impairment while a few cause no vision problems and are discovered during a routine eye examination. Other dystrophies may cause repeated episodes of pain without leading to permanent loss of vision.
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Common Corneal Dystrophies
Fuch's Dystrophy
Fuchs' dystrophy is a slowly progressing disease that usually affects both eyes and is slightly more common in women than in men. Although doctors can often see early signs of Fuchs' dystrophy in people in their 30s and 40s, the disease rarely affects vision until people reach their 50s and 60s.
About Fuchs’ Dystrophy
An inherited condition, Fuchs’ Dystrophy affects the endothelium, the delicate innermost layer of the cornea. Fuchs dystrophy occurs when the endothelial cells gradually deteriorate over time. As more endothelial cells are lost over the years, the endothelium becomes less efficient at pumping water out of the stroma. This causes the cornea to swell and distort vision. Eventually, the epithelium also takes on water, resulting in pain and severe visual impairment.
Epithelial swelling damages vision by changing the cornea's normal curvature, and causing a sight-impairing haze to appear in the tissue. Epithelial swelling will also produce tiny blisters on the corneal surface. When these blisters burst, they are extremely painful.
Symptoms
In the early stages of Fuchs’ dystrophy, patients notice an increase in the appearance of glare and an increased sensitivity to light. As the condition progresses, the patient will wake up with blurred vision that will gradually clear during the day. This occurs because the cornea is normally thicker in the morning; it retains fluids during sleep that evaporate in the tear film while we are awake. As the disease worsens, this swelling will remain constant and reduce vision throughout the day.
Treatment
When treating the disease, doctors will try first to reduce the swelling with drops, ointments, or soft contact lenses. They also may instruct a person to use a hair dryer, held at arm's length or directed across the face, to dry out the epithelial blisters. This can be done two or three times a day.
When the disease interferes with daily activities, a person may need to consider having a corneal transplant to restore sight. The short-term success rate of corneal transplantation is quite good for people with Fuchs' dystrophy. However, some studies suggest that the long-term survival of the new cornea can be a problem.
Lattice Dystrophy
Lattice dystrophy gets its name from an accumulation of amyloid deposits, or abnormal protein fibers, throughout the middle and anterior stroma. During an eye examination, the doctor sees these deposits in the stroma as clear, comma-shaped overlapping dots and branching filaments, creating a lattice effect. Over time, the lattice lines will grow opaque and involve more of the stroma. They will also gradually converge, giving the cornea a cloudiness that may also reduce vision.
Although lattice dystrophy can occur at any time in life, the condition usually arises in children between the ages of two and seven.
Symptoms
Recurrent Epithelial Erosion
In some people, these abnormal protein fibers can accumulate under the cornea's outer layer—the epithelium. This can cause erosion of the epithelium. This condition is known as recurrent epithelial erosion. These erosions:
- Alter the cornea's normal curvature, resulting in temporary vision problems; and
- Expose the nerves that line the cornea, causing severe pain. Even the involuntary act of blinking can be painful.
Treatment
To ease this pain, a doctor may prescribe eye drops and ointments to reduce the friction on the eroded cornea. In some cases, an eye patch may be used to immobilize the eyelids. With effective care, these erosions usually heal within three days, although occasional sensations of pain may occur for the next six-to-eight weeks.
Scarring Under the Epithelium
By about age 40, some people with lattice dystrophy will have scarring under the epithelium, resulting in a haze on the cornea that can greatly obscure vision. In this case, a corneal transplant may be needed. Although people with lattice dystrophy have an excellent chance for a successful transplant, the disease may also arise in the donor cornea in as little as three years.
In one study, about half of the transplant patients with lattice dystrophy had a recurrence of the disease from between two to 26 years after the operation. Of these, 15 percent required a second corneal transplant. Early lattice and recurrent lattice arising in the donor cornea responds well to treatment with the excimer laser.