Fuchs Dystrophy
Author: Sherman Winston Reeves, M.D., M.P.H.

Definition:

Fuchs dystrophy is an inherited disease of the cornea in which the inner most layer of the cornea, called the endothelium, becomes dysfunctional and may result in decreased vision.

The front part of a normal eye is filled with fluid called the aqueous. However, the cornea, which separates the outside air from the aqueous fluid inside the eye, must stay relatively dry in order to maintain its clarity. To accomplish this task, the inside of the cornea is lined with a specialized layer of cells called the endothelium. The endothelial cells function as one-way pumps, drawing fluid out of the cornea and pumping it back inside the eye. By so doing, the cornea, despite being in direct contact with the aqueous eye fluid, stays relatively dry and clear.

In Fuchs dystrophy, the endothelial cells are slowly replaced with small collagen bumps called guttata. Guttata may first appear in the cornea in the 20s and 30s, though rarely cause any symptoms until later in life. As a person ages, the guttata may slowly increase in number and size. In the process, the endothelial cells surrounding them may slowly die. When a critical number of endothelial cells are lost, usually by the age of 50 to 60 years, the pump function of the endothelium may be overwhelmed and the cornea starts to swell with eye fluid. As the swelling worsens, the vision may start to decrease. In cases where large amounts of guttata exist on the cornea, the vision may also become compromised even without corneal swelling from irregular scattering of light passing through the dense guttata layer.

Cause of Fuchs Dystrophy:

Fuchs dystrophy caused by an inherited malfunction in the way the inner lining cells of the cornea behave. The gene is transferred from parent to child in an autosomal dominant fashion, which means that each child of an affected parent has a 50% chance of developing the disease. Though many family members may have Fuchs dystrophy, its effects may vary greatly from one family member to the next. As such, some individuals with Fuchs will have signs of the disease visible only to a doctor examining their corneas with a slit lamp , and will never suffer any visual loss from the disorder. Other individuals who have worse forms of the disease may suffer slowly progressive visual loss.

Symptoms (What you may experience if you have a vitreous detachement, retinal tear or fuchs dystrophy):

Fuchs dystrophy is usually asymptomatic until a person reaches 50 to 60 years of age. For individuals with worse forms of the disease, the endothelial cells of the cornea may become so compromised enough that the cornea begins to swell with eye fluid. This swelling is usually gradual over many weeks or months, and may be so slow that it is not immediately noticeable. When the swelling becomes advanced enough, a person may notice that the vision seems not as sharp as it used to be. The vision may often be worse in the morning, due to swelling of the cornea overnight, and improve as the day goes on while the eyes are open and exposed to the drying effect of the air. Fuchs patients may also complain of more glare in sunlight conditions and more difficulty seeing in low light conditions. As the swelling becomes severe, the vision may decline greatly, causing true impairment of a person’s daily living activities.

Examination for Fuchs Dystrophy:

Tests you may have at the doctor’s office:

To determine if you have Fuchs dystrophy, your eye doctor will perform an eye evaluation. Your visual acuity will be measured with an eye chart. Other general eye tests may include eye pressure measurement, pupil testing, a peripheral vision check and range-of-motion testing of the eye muscles. Your doctor will perform a slit lamp examination to examine the front part of the eye and examine the cornea for signs of Fuchs dystrophy, such as guttata and corneal swelling. Your eyes may also be dilated as part of a complete eye examination to help the doctor view the vitreous and retina in the back part of the eye. The thickness of your cornea may be measured using a pachymeter, which helps your doctor assess the presence and amount of corneal swelling. Your doctor may also obtain an evaluation of the health and number of the corneal endothelial cells using a specular microscope.

Treatment of Fuchs dystrophy:

In the early phases of Fuchs dystrophy, typically no treatment is required. In some individuals, however, the disease may advance to the point where the cornea begins to swell. For these people, saltwater drops and salt ointment may help pull fluid out of the cornea and improve the vision. Drying the eyes briefly with a hairdryer sometimes can also help, though the effects of both drops and drying is typically short lived.

When the vision becomes compromised significantly, surgery may be used to cure Fuchs dystrophy. Two surgical approaches may be used. In Descemets Stripping Endothelial Keratoplasty (DSEK), the endothelial lining of the cornea is removed and replaced with a small disc of endothelial cells from a donor. The replacement of the malfunctioning endothelial cells allows the cornea to once again become clear by restoring the lost endothelial fluid pumping function. DSEK is performed through small incisions and has a relatively fast recovery period. Usually, the cornea can be greatly cleared by 4 to 6 weeks after the procedure. Occasionally, however, the donor endothelial cells become dislodged from the inside of the cornea and have to be repositioned surgically or replaced entirely. For cases of severe cornea swelling or when scarring of the cornea has also developed, Penetrating keratoplasty(PK) may be used. During a PK, the entire cornea is removed, much like a man-hole cover, and replaced with a complete donor cornea. The donor tissue is secured in place with many sutures which are finer than a human hair. These sutures remain in place for several months, and then are slowly removed over the course of about a year. As such, the recovery period for PK is much longer than for DSEK. However, PK is sometimes the best option for visual rehabilitation, even in spite of the longer recovery.

Prognosis (How Fuchs Dystrophy an affects vision over the long-term:

Though Fuchs dystrophy can be seen in younger people, it typically causes symptoms only in individuals older than 50 to 60 years of age. Many people with Fuchs dystrophy have mild version of it. As such, most will never even know that they have the disease, nor will they ever suffer symptoms from it. Individuals with more severe forms of Fuchs, however, may start to notice a decline in vision from it when they reach middle age. This visual decline can be mild, and only noticeable in certain lighting conditions, or, in the case of advanced disease, can cause profound limitation of the vision as the cornea swells.

Prevention of Prevention of Fuchs Dystrophy:

As Fuchs dystrophy is an inherited disorder, there is no way to prevent the disease from occurring. Regular examinations by an eye doctor, however, can help identify Fuchs dystrophy early and address any complications of the disease before they become visually disabling.

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