Adults suffering from retinitis pigmentosa (RP), a group of inherited diseases that may cause blindness, can slow their loss of vision by taking a daily supplements of vitamin A and avoiding high doses of vitamin E, it was reported yesterday by Harvard University researchers.
The $5-million study provides the first useful treatment for retinitis pigmentosa, which afflicts 100,000 Americans. The disease gradually destroys vision cells in the retina at the back of the eye.
Patients suffering from retinitis pigmentosa generally report night blindness in adolescence and lose peripheral and finally central vision as they age, typically going completely blind between 50 and 80.
Adult patients in the study who supplemented their daily diets with 15,000 International Units of vitamin A had, on average, a 20 percent slower annual decline of remaining retinal function than those not taking the high dose, according to Dr. Eliot L. Berson, the study's principle investigator. The study was published in the Archives of Opthalmology.
Based on this finding, Dr. Berson and his colleagues estimate that an average patient in the study who started taking a supplement at age 32 would retain some useful vision until age 70; a patient not on this dose would lose useful vision by 63.
Moreover, it was found that retinitis pigmentosa appeared to progress faster in adults taking high-dose vitamin E supplements. However, there was no evidence that normal dietary or small supplemental amounts of vitamin E have an adverse affect, Dr. Berson said.
Dr. Berson cautioned that patients should take only the form and dosage of vitamin A supplement recommended by the study. Other available forms of vitamin A, such as those found in retail outlets, were not part of the study. High doses of the vitamin have been associated with potentially harmful side effects, he noted.
Patients and health care professionals should call the RP Foundation Fighting Blindness at 800-683-5555 for complete information before starting treatment.