FAMILY MEDICINE® COLUMN
By Martha A. Simpson, D.O., M.B.A.
Assistant Professor of Family Medicine
Ohio University College of Osteopathic Medicine

RETINITIS PIGMENTOSA -- NO CURE YET, BUT RESEARCH IS PROMISING

Question: Recently I’ve seen some articles about a retinal computer chip that supposedly allows previously blind individuals with retinitis pigmentosa to regain some sight. Since I have a relative with RP, I’m very interested in finding out how promising this and other research might on RP be.

Answer: In order to answer your question concerning retinal implants for the treatment of retinitis pigmentosa (RP), I first need to give you some background on this disorder. RP is just one of a number of diseases that can cause blindness. It runs in families and is believed to result from defects in one of several genes. In RP the retina -- a layer of “photoreceptor” nerve endings in the “back” of the eye -- degenerates.

These photoreceptor cells are called “rods” and “cones.” The rods are responsible for “black and white” night vision and the ability to see out of “the corner of your eye.” Doctors call this “peripheral vision.” Rods are located throughout most of the retinal surface but more thickly on the edges, or periphery. The cones -- concentrated in a central portion of the retina called the fovea -- work best in the light and allow you to see in color.

The rods and cones convert the light entering the eye to electrical signals that send the visual message to the brain via the optic nerve. Usually, the first indication of the disease is the deterioration and eventual loss of low-light vision. Next, the disease typically results in gradual loss of peripheral eyesight causing “tunnel vision.” Later in the disease, color vision is lost and finally, central vision can be lost. While symptoms of RP may first appear in childhood, visual impairment does not usually occur until early adulthood.

There are many other types of visual loss and blindness, such as cataracts, glaucoma, and blindness from diabetes or damage to the optic nerve.

Currently several retinal implant research projects are going on worldwide. The retinal implant research involves the development of a microchip that could be implanted in the retinal region that would react to light in a fashion similar to retinal tissue. This first chip sends an electronic signal to a second chip that relays the message to the brain, causing sight. There are also laser and battery components to this device. This research is very promising, and some limited human trials are in process. However, it will probably be over five years before a working retinal implant is fully developed.

Retinal cell transplantation is another RP treatment that is currently being researched. It involves transplanting healthy retinal cells into the diseased retina. Testing in humans has begun, and the early results are encouraging.

Since the mutant genes in this genetic disorder have been identified, gene therapy also appears very promising. The problem is figuring out how to deliver the new genes to the retina.

Vitamin A has been used to slow the progression of RP, but it can be toxic if taken in high dosages. Always check with your doctor before beginning high dose vitamin A therapy.

So here it is in a nutshell: RP is inherited, so know your family medical history. If you have a positive family history, get regular eye exams, and report any visual losses promptly. Discuss taking vitamin A with your doctor. Follow the research, but be wary of “quick cures” or pie-in-the-sky promises about RP treatments. Learn everything you can about RP.

Family Medicine® is a weekly column. To submit questions, write to Martha A. Simpson, D.O., M.B.A., Ohio University College of Osteopathic Medicine, P.O. Box 110, Athens, Ohio 45701. Past columns are available online at http://www.FamilyMedicineNews.org.