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June 14, 1993
Information for Doctors Who Follow Patients with Retinitis Pigmentosa
This letter is to inform you of the finding from a clinical trial of nutritional supplements for adults with the common forms of retinitis pigmentosa. This trial was supported by the National Eye Institute, a component of the National Institutes of Health, and in part by the RP Foundation Fighting Blindness*.
In this trial the course of retinal degeneration was evaluated in 601 patients, aged 18-49 years, who were assigned randomly to different combinations of vitamin A and vitamin E as a daily supplement. Depending on time of enrollment in the study, patients were followed for 4-6 years. Ninety-five percent of those enrolled completed the study, and no adverse side effects were observed.
The course of retinal degeneration as monitored with the electroretinogram (ERG) was slower on average among patients taking 15,000 IU of vitamin A daily versus those not taking this dose. The results also suggested that the course might be faster on average among patients taking a daily supplement of 400 IU of vitamin E versus those not taking this dose. Rates of loss of visual field area were consistent with the ERG findings.
Based on these findings, it is recommended that most adult patients with the common forms of retinitis pigmentosa take a supplement of 15,000 IU of vitamin A daily under the supervision of their eye care professional and avoid use of high-dose supplements of vitamin E. In the context of this treatment, a beta-carotene supplement is not a suitable substitute for vitamin A in the palmitate form.
A single capsule containing 15,000 IU of vitamin A in the palmitate form will soon be available commercially.
Optimal benefit occurred among patients with a total daily intake (diet + capsules) of 18,000 IU of vitamin A daily and a higher intake provided no greater benefit. Therefore, patients should not take vitamin A supplements greater that the 15,000 IU used in this study nor should they modify their diet to select foods with high levels of vitamin A. It should also be noted that a total daily intake of greater than 25,000 IU of vitamin A daily has been reported to have potentially harmful side effects - including liver disease - when taken over the long term. Because of the potential for birth defects, women who become pregnant should be advised to discontinue this dose of vitamin A. Since patients under age 18 were not evaluated in this study, no formal recommendation can be made for patients with retinitis pigmentosa under this age.
A more comprehensive description of this study and its results are published in the June issue of the Archives of Ophthalmology to which you are referred.
Carl Kupfer, M.D.
National Eye Institute
National Institutes of Health
Eliot L. Berson, M.D.
Professor of Ophthalmology
Harvard Medical School
Massachusetts Eye & Ear Infirmary
*RP Foundation Fighting Blindness is now The Foundation Fighting Blindness.