(January 29, 2009 - Insidermedicine) Watch Dr. Gerry Chader, MD, Ph.D., whose research focuses on the cause, prevention, treatment, and cure of retinal disease, discuss retinitis pigmentosa. Dr. Chader is a Chief Scientist at the Doheny Retina Institute at University of Southern California Medical School.
On a recent trip to Los Angeles, we caught up with Dr. Gerry Chader, who is the chief scientist at the Doheny Retina Institute at the University of Southern California School of Medicine. Dr. Charder’s research focuses on the cause, prevention, and treatment, as well as the cure of retinal disease.
What is retinitis pigmentosa?
Dr. Chader: Retinitis pigmentosa is really a family of diseases, it’s a catch-phrase for a grouping. Right now there are well over 100 gene mutations that are known to ultimately result in one form or another of retinitis pigmentosa. What is noticed is that very often since it strikes very early in life, either at birth or soon thereafter, a parent will notice that a child is clumsy at dawn or dusk or under low light conditions, is bumping into furniture, is having a little trouble managing mobility, and they’re thought of as either a slow or clumsy or something like that and in fact they’re not, in fact these are the early signs of retinitis pigmentosa. The two hallmarks of RP are that there is a loss of peripheral vision (eg, they wouldn’t see a baseball coming at their head from somewhere out in left field) and secondly that because the rod photo-receptor cells are the main cells affected, and are in the periphery, (thus, peripheral vision is lost first) also rod photoreceptor cells subserve dim vision, whereas bright light vision, daylight vision, is mainly subserved by the cone photoreceptor cells. With rods going awry (genetic mutation mainly affecting the functioning of the rod cells) the peripheral vision and the dim light vision are the first to go. And so at age 3 or 4 a parent is saying “Johnny, get up out of that bed, and get into the bathroom and brush your teeth” and Johnny stumbles and goes into the door.
Retinitis pigmentosa is silent, there is no pain, it usually comes on quite slowly, so a parent will often take the child in to a pediatrician rather than an ophthalmologist not understanding that really this is an ocular condition, and hopefully, then, the pediatrician realizes in fact what is going on, there is an eye exam and that can’t be an eye exam just for acuity, because very often the acuity in a RP patient is very good. I know adults with various forms of retinitis pigmentosa who have what is called shotgun or tunnel vision (a field of view of only 5 or 8 degrees) but they can read the fine print of the New York Times because their visual acuity is just fine in the macula, it’s the rest of the retina that is problematic. These people can’t drive, since anything coming at them out of their peripheral vision is not seen at all, but with scanning they can do pretty well at reading and face recognition and other things like that.
The other more obvious problem in retinitis pigmentosa is presented in congenital forms of RP. There is a form of RP called Leber’s congenital amaurosis (LCA), and basically the child is born blind and has wandering eye (nystagmus), where the eyes wander back and forth. This is a lot easier to spot because the child is not focusing on the parent’s face, the eyes are wandering back and forth after a few months after birth. Pretty quickly, these children are taken in to the ophthalmologist.
If I had retinitis pigmentosa...
Dr. Chader: There is one treatment right now that is thanks to the good research of Dr. Eliot Berson at Harvard’s Massachusetts Eye and Ear Infirmary in Boston: back in the 1990s Dr. Berson found that many of his patients were on higher regimens of vitamins, and some of these seemed to do a bit better, and so he chose two vitamins, Vitamin A and Vitamin E, to do an in-depth study of, and found that in some patients on a very high vitamin A regimen (but still safe), the vision was improved, but only in some patients, and the vision was only slightly improved such that vision in those patients continued to decline but at a slower pace, so his estimate was 8-10 years of prolonged vision in those patients. So to date, the only treatment for retinitis pigmentosa is in this vitamin A treatment. That doesn’t mean that hopefully next year or the year after this is going to be the only treatment because we have at least 5 different directions in different areas of research where there is good hope for treatments and cures coming.