What is Fuchs’ Dystrophy?
Corneal dystrophies are a debilitating group of progressive diseases that can ultimately deprive a person of sight. The cornea, which forms the front of the eye, is a window for vision, and dystrophies due to intrinsic defects in the corneal tissue cause this window to become opaque and hazy. Fuchs’ dystrophy, also known as Fuchs’ corneal endothelial dystrophy (FCED), is amongst the most commonly diagnosed corneal dystrophies requiring corneal transplantation. The ophthalmologist Ernest Fuchs first described the disease in 1910.
Who gets it?
The disease is rare, and it is difficult to predict who will get it. We know that it affects women more than men (3:1 ratio), older adults (older than 50 years of age), and those with a family history. There are forms in which there could be up to a 50% chance of transmission to children of parents with Fuchs’ dystrophy. Most cases, however, occur sporadically.
What causes it and how does it progress?
Although the cause of Fuchs’ dystrophy is still being studied, there are characteristic findings associated with it: small outgrowths on Descemet’s membrane called “guttae” or “guttata”, thickening of Descemet’s membrane, and defects in the endothelial cells (Figure 1).
Descemet’s membrane is a thin corneal layer between the endothelial cell and the stromal layers of the cornea. Endothelial cells make up the backside of the cornea and function as a barrier and pump for keeping fluid out of the cornea and maintaining corneal clarity. As guttae accumulate on Descemet’s membrane, patients experience progressive loss and change in endothelial cells. Dysfunction of endothelial cells causes corneal swelling, which distorts vision. First, the back of the cornea swells, and eventually, swelling can reach the epithelial cells at the front of the cornea. Swelling can range from mild moisture accumulation, to painful “bullae”, or blisters. In very late-stage disease, significant corneal scar tissue can form and dramatically reduce vision. The progression to late stage Fuchs’ varies from person to person, but usually takes a couple of decades.
What are signs and symptoms?
A patient may be asymptomatic for years despite having guttae. Initial symptoms, including blurry, hazy, or cloudy vision, are typically due to corneal swelling from dysfunction of the endothelial cell layer. Patients may also experience glare or halos around light in the early stages just from the density of guttae. New studies suggest that patients can get glare and higher order aberrations from guttae without any corneal swelling. Symptoms tend to be worse on awakening, but usually improve throughout the day. This is because the closure of eyelids during sleep results in the accumulation of fluid in the cornea. For the same reason, humid weather can also worsen symptoms. As the disease progresses, poor vision may last longer into the day. There may be associated pain if blisters develop.
How is it diagnosed?
The presence of any of the above signs and symptoms, especially with a family history of Fuchs’, should prompt a consult with an ophthalmologist who will diagnose the disorder and follow its progression with regular checkups. An ophthalmologist will conduct a microscopic slit-lamp examination of the eyes, looking for guttae and Descemet’s membrane thickening (Figure 2).
Special tests may be done to measure corneal thickness, a marker of swelling, or count endothelial cells to track disease progression (Figure 3 and 4).
How is it managed?
Management can be medical or surgical depending on symptoms. Patients may have mild or slow progression of disease that can be managed medically including over the counter salt solution drops (5% NaCl) to reduce corneal edema.
When there is late-stage disease, a corneal transplant may be necessary to improve vision. A corneal transplant replaces the patient’s corneal tissue with human donor corneal tissue. Donor corneas are readily available via excellent eye banks throughout the United States. The surgery is outpatient surgery with regular follow-up appointments and suture removal during the subsequent months. The postoperative healing of the cornea and vision stabilization can take up to a year.
Great strides have been made in the last decade in corneal transplantation surgery, giving patients better treatment options. Patients used to be limited to penetrating keratoplasty (PK), a full-thickness replacement of the cornea. We now have newer surgeries known as endothelial keratoplasty (EK), which is a partial-thickness transplant that replaces only the damaged part of the cornea (the endothelial layer). The different types of EK are DSEK (Descemet’s-Stripping Endothelial Keratoplasty) and DMEK (Descemet’s Membrane Endothelial Keratoplasty). The techniques vary by thickness of the transplanted tissue. The type of EK most appropriate is determined by the corneal surgeon and is variable on a case to case basis. Both types of EK surgeries provide comparable long-term visual results. In both surgeries, the patient’s diseased Descemet’s membrane and endothelial cells are stripped from the inner layer of their cornea. The thin lamellar donor graft is then inserted into the eye and positioned onto the back of the patient’s cornea via a gas or air bubble. The patient is then instructed to lie in a face up position for several hours post surgery during which time the bubble supports the graft until the new endothelial cell pumps begin to wake up and naturally adhere to the back side of the recipient cornea. Occasionally, the doctor may replace another air bubble into the eye the next day to allow more time for the graft to adhere. Visual recovery is on the order of 1-2 weeks in DMEK and 2-3 months in DSEK surgery. Rejection risk is still a possibility in EK surgery but has a much lower rate than traditional full thickness PK surgery.
Other surgical considerations depend on the presence of cataracts. Cataract surgery can worsen Fuchs’ dystrophy because of damage to the endothelial cell layer. For this reason, patients with cataracts and Fuchs’ requiring surgical intervention are often recommended to undergo cataract surgery before or at the same time as corneal transplantation to ensure the best outcome for the transplant.
Patients should work with an ophthalmologist to determine the best management plan. Ultimately, vast improvements in treatment options have given many Fuchs’ dystrophy patients the exciting opportunity to regain vision with improved healing times and reduced infection and rejection of the graft.
Citations: Figure 2 and 4 are from Zhang J, Patel DV. The pathophysiology of Fuchs’ endothelial dystrophy—a review of molecular and cellular insights. Exp Eye Res. 2015 Jan
Priscilla Q. Vu, MS
University of California, Irvine School of Medicine
Marjan Farid, MD
Director of Cornea, Cataract, and Refractive Surgery
Vice-Chair of Ophthalmic Faculty
Director of the Cornea Fellowship Program
Associate Professor of Ophthalmology
Gavin Herbert Eye Institute, University of California, Irvine