By Caterina Sarnicola
Fuchs endothelial dystrophy is a hereditary eye disease that was first described by Professor Ernst Fuchs more than 100 years ago. FED is a progressive degeneration of the endothelium, the innermost layer of the cornea.
The cornea is the clear “window” of the front of the eye. Its inner part, the endothelium, is a single layer of cells whose function is to pump fluid out of the cornea in order to keep it crystal clear.
In patients with FED, the endothelial cells slowly deteriorate and dewdrop-shaped outgrowths called guttae accumulate on the Descemet's Membrane (the layer just underneath the endothelium). The damaged endothelium stops pumping fluid properly and the cornea begins swelling. As the disease progresses, the cornea becomes cloudy and thicker (corneal edema) and vision is reduced.
In advanced stages, epithelial blisters can form on the surface of the cornea causing pain and further worsening in vision.
CAUSES About 30% of patients with FED have a known family history. The genetics of this disease are complex. Family members can be affected with variable severity or not be affected at all.
This disease is more common in women and usually affects people in their 50s and 60s although there is a very rare type of FED characterized by early onset in young adulthood.
SYMPTOMS Both eyes are affected but the condition is often asymmetric. In fact, symptoms usually appear in one eye before the other. In the early stage, FED may produce no symptoms and it may be diagnosed as an incidental finding at an eye screening or during a preoperative evaluation for cataract surgery.
As FED progresses symptoms usually are:
- Blurred vision, usually worse in the morning, resulting from fluid collecting in the cornea during sleep. During the day this excess fluid evaporates and vision gradually improves. In advanced stage of the disease vision may be affected for the entire day.
- Glare and sensitivity to light (often causing difficulty driving at night)
- Fluctuating eyesight
- Pain in the eye, when blisters on the surface of the cornea have formed (advanced stage)
Symptom severity can be influenced by climatic conditions and often worsen on humid or rainy days or after a hot shower.
DIAGNOSIS AND FOLLOW-UP Both diagnosis and follow-up require:
- Visual acuity tests (reading an eye chart)
- Slit-lamp examination which allows the ophthalmologist to examine the cornea under high magnification and look for the characteristic signs of FED
- Pachymetry to measure the thickness of the cornea
- Confocal microscopy to study the number, shape and size of the endothelial cells
TREATMENT There are different therapeutic strategies according to the FED stage, however currently there is no treatment that can halt or reverse the course of the disease.
The progression of the FED from early to late stage may take from 10 to 20 years. Fortunately, in the majority of patients, the disease does not progress so far that corneal surgery is needed.
- No therapy is required until the first symptoms appear
- Medical management includes:
- Concentrated salt solution eye drops or ointments to help reduce fluid inside the cornea
- Therapeutic soft contact lenses to relieve pain due to blisters on the surface of the cornea
- In late stage FED, when the disease interferes on the quality of life of patients, surgery is needed. The most common surgical treatment is corneal transplantation; surgical options include:
- Penetrating keratoplasty (PK). This procedure replaces the entire cornea and in the past it was the only option for transplants. PK does have the potential to provide clear vision after healing, however it is no longer the first choice treatment because of the high risk of rejection and the long visual recovery (1 year or more).
- Endothelial keratoplasty (EK). This procedure replaces the inner layer of the cornea. Two techniques may be considered: Descemet stripping endothelial keratoplasty (DSEK) and Descemet membrane endothelial keratoplasty (DMEK), which vary in the amount of donor corneal stroma transplanted. Both are very successful with visual recovery in weeks to months. The corneal tissue is held in place by an air bubble; occasionally more than one air bubble is needed. Patients must lie flat on their backs after surgery to encourage the corneal tissue to “stick” to their own corneas.
This is currently the standard of care.
NEW APPROACHES FED is the most common reason for corneal transplantation in the United States. Thanks to the introduction of the new transplantation techniques, which replace only the unhealthy layer, the results are very good but some issues still remain. The donor corneas are expensive and there is a limited supply in some areas of the world. Furthermore, patients must apply steroid eye drops for the rest of their lives to prevent rejection of the transplanted corneal tissue and these medications are known to have side effects.
Some corneal specialists are developing new surgical approaches to reduce the need for corneal transplants:
- Descemet stripping without endothelial keratoplasty. This surgical procedure consists in removing a few square millimeters of corneal endothelium in order to allow repopulation from the surrounding healthier tissue. Kathryn Colby, MD, PhD, the Louis Block professor and chairman of the Department of Ophthalmology and Visual Science at the University of Chicago, performed this new procedure, combined with cataract surgery, on 11 patients (13 eyes) in 2014-2015. The results are published in the journal Cornea; 77% of treated eyes had clear corneas and improved visual acuity without the need for a corneal transplant. Professor Colby and her colleagues have already identified certain criteria that are necessary in order for this surgery to be successful.
- Rho kinase inhibitor eye drops. The topic application of these eye drops seems to stimulate endothelial regeneration; currently new clinical studies are ongoing. This medication is not FDA-approved in the United States at the current time.
- Injection of cultured endothelial cells. This procedure consists in injecting cultured endothelial cells inside anterior chamber and is being performed in Japan. The aim is to have an easier procedure than the endothelium transplant and to save corneal tissues because one donor cornea could provide enough cells to treat approximately 100 patients. The results of this research are not published yet.
SUMMARY Fuchs dystrophy is a common corneal condition. Modern corneal transplantation techniques are effective but recent work suggests corneal transplantation may not be needed.
To schedule an appointment with Dr. Colby for an evaluation, please contact Nicole Mazzone at 773-702-5984.