Retinitis Pigmentosa- Separated Facts from Fear

Being diagnosed with Retinitis Pigmentosa can be very frightening, not only because it is a serious condition, but also because there is so much old and incorrect information associated with the diagnosis. Before you reach too many conclusions, wait. It will be much less scary if we take a few minutes to separate fact from fiction. It is very important to know not only what the diagnosis means, but also what it does not mean. For instance, it does not mean that you are going to lose your vision soon. Not this year, and probably not even in the next 10 years. It is true that there are not many treatments at this time, but this may not be the case in the future, during the time that you still have saveable, treatable vision. It is also possible to adapt quite well to your limitations with help from people who know the problems, and have perhaps dealt with them personally. So, let's go over some basic information. The following is a brief review. Additional information, and resources are available from the links on the left.

What is RP?-

Retinitis Pigmentosa is a large group of inherited diseases, called "retinal dystrophies", causing retinal malfunction and gradual loss of vision. There are many different forms, but all cause a gradual decline of vision, which eventually over years results in severe or even total vision loss. Most types of RP result first in decreased night vision and peripheral (side) vision. Only a few types cause early loss of central vision. Progression is usually extremely slow with changes noted over years or even decades. Rapid vision loss over weeks or months is extremely rare.

The many subtypes of retinal dystrophy-

A "dystrophy" is a disease caused by an abnormality in a gene, causing some part of the body to malfunction. There are many genes controlling the function of the retina, so a retinal dystrophy is a gene abnormality resulting in retinal malfunction. There are dozens genes controlling the retina, and there are dozens of different types of retinal dystrophy, all with very long and strange sounding names. For simplicity, they are collectively referred to as Retinitis Pigmentosa, or "RP". Some cause malfunction of the "rods", retinal light receiving cells that control most of our night vision and side vision. RP affecting these genes are call "rod" or "rod-cone" dystrophies, whose first symptoms are problems with the night and side vision. This is sometimes called "night blindness". Other dystrophies cause malfunction of the "cone" light receptors, which control the central, color, and daytime vision. "Cone" dystrophies result in earlier loss of central vision, color vision, and sometimes light sensitivity or "day blindness".

RP is usually an inherited disease-

RP is usually an inherited disease, meaning that the abnormal gene is passed along in a family from generation to generation. Each of us has two copies of every "autosomal" gene, one from our mother and one from our father. If the abnormal gene is "dominant", then it only takes one abnormal copy to cause the disease symptoms. If you "do the math", it turns out that dominant RP shows up in about 1/2 of an affected person's children. Occasionally, RP appears "out of the blue", with no previous family history. Like dominant inherited RP, this is usually the result of one abnormal gene copy, and it is usually passed one from the first affected person in a dominant pattern.

If the abnormal gene is "recessive", it means that you need two copies with the same abnormality to have the disease symptoms, one bad copy from each of your parents. These cases are very rare. If you have recessive RP, and your spouse does not, then each of your kids will have one abnormal gene, from you, and in all liklihood one normal gene from your spouse. Your kids will "carry" the gene but will not have the disease. Unless they marry a blood relative, it is very unlikely that they will pass the disease on to their children, although about half of there children may carry the gene. Two carrier parents are at risk of having one fourth of their children affected and one half of their kids carriers.

There is one other main inheritance pattern, called "X linked recessive". Some genes are carried in the female "X" chromosome. This means that males have only one copy of that gene, from their mother. Women have two copies, one from mom, and dad gives them his only copy. If mom has an abnormal "X" gene, she may pass it along to half of her sons (it is almost certain that her other copy is normal), and they would have the disease symptoms. Half of her daughters will be carriers, like her. As you can see, the inheritance questions get very complex, and you should talk in detail with your doctors about the inheritnace questions that may apply to your situation.

Could it be something besides RP?

Yes. There are many other gene abnormalities that affect vision, and there are infections and inflammatory diseases that can mimick RP. Such inflammatory diseases inlude congenital rubella (German Measles), syphilus, tuberculosis, various viral diseases, and even some rheumatoid diseases. Other gene abnormalities include "X-linked retinoschisis", which causes retinal detachment and macular (central vision) malfunction. There is a group of diseases called "congenital stationary night blindness", which as the name suggests causes night blindness but does not progress much over time. Juvenile Macular Degeneration, Stargardt's Disease, Fundus Flavimaculatus, and Pattern Macular Dystrophy are some of the many names you may hear as you learn more about RP. These are all important but very different diseases that need to be considered as we deal with your individual circumstance. Your diagnosis can usually be very precisely determined by the specialized testing that is now available.

What tests are used to diagnose RP?

RP itself is a group of diseases that all cause some abnormality of the electrical transmission of vision in the photoreceptor cells in the retina. Other diseases cause transmission abnormalities of other types or in other locations in the retina. The type and location of electrical malfunction can be detected using tests that measure electrical activity. This is called electrodiagnostic testing. The main types are "Electroretinography" or ERG, "Electro-Oculography" or EOG, and occasionally "Visual Evoked Response" or VER. These are very delicate tests to do, requiring a very specialized lab set up, but except for involving bright lights, they are not unpleasant for the patient. In order to obtain the best quality testing, we often send patients to an academic center where this testing is done frequently. The Berman-Gund Laboratory at Massachusetts General Hospital has new ERG technology that can help provide detailed information capable of predicting, within a few years, how many years of useful vision a patient may expect. This information can be invaluable, not only to allay the fear of the unknown, but also to help in life and career planning. Other tests include visual field testing to measure side vision and various photographic tests, all of which are done here in our offices. Electrodiagnostic tests are done initially at the time of diagnosis, but do not usually need to be repeated very often. Other tests are done to follow functional performance, such as to evaluate a patient for driving or specific job tasks, or to evaluate common problems that sometimes arise in RP patients, such as cataracts, glaucoma, or macular edema.

Other conditions may be more common in RP patients-

While treatment of the RP itself is currently limited to vitamin therapy, certain other very treatable conditions are more common in people with RP. Certain types of cataracts occur sooner and may progress more quickly in patients with RP. When necessary, this is easily treated with cataract surgery. RP patients may also develop swelling (edema) in the macula, the reading portion of the retina. This can be treated with eyedrops or pills to decrease inflammation. Glaucoma may be more common, and certainly can progress more rapidly in RP patients, and this is treated with drops, laser, or surgery. Because of these issues, it is very important for RP patients to have regular eye checkups.

What about current RP treatment?

Currently, the mainstay of RP treatment is limited to dietary supplementation with Vitamin A palmitate. This is a DIFFERENT form of Vitamin A than the beta-Carotene or regular Vitamin A found at the local pharmacy. These common forms are WORTHLESS in RP treatment. Some years ago, a large multi-center study found that extra Vitamin A in the highly soluble palmitate form increased electrical activity in the retina by several microvolts. In many patients this may be enough to add several years of useful vision in the patient's life. The same study found that supplemental vitamin E not only didn't help, but may actually be detrimental. The learning point here is not just to avoid high dose Vitamin E, but to be very careful about chasing every new dietary fad without waiting for experimental support. Vitamin A Palmitate is not ea-sy to find, but it can be easily obtained from Akorn Pharmaceuticals (800-932-5676). Ask for "Palmitate-A 15000". You should take 15000 units per day. Less is less effective and more can be toxic.

Other treatments will likely be available in the future-

RP in most forms progresses very slowly. During the lifetime of a patient diagnosed with RP today, it is very likely that new and meaningful treatments for RP will appear. Even now, there are several avenues of treatment research. New nutritional studies are currently underway. Gene research is very complex, but animal experiments have yielded astonishing early results. There are also ongoing studies into artificial retinal stimulation and even bypassing the retina altogether using video technology to stimulate the visual areas in the brain. We will keep you informed about these things at your visits and through this website.