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 nutritionalsupplements for adults with the common forms of retinitis pigmentosa. Thistrial was supported by the National Eye Institute, a component of the NationalInstitutes 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 ofvitamin A and vitamin E as a daily supplement. Depending on time of enrollmentin the study, patients were followed for 4-6 years. Ninety-five percent ofthose 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 dailyversus those not taking this dose. The results also suggested that the coursemight be faster on average among patients taking a daily supplement of 400IU of vitamin E versus those not taking this dose. Rates of loss of visualfield area were consistent with the ERG findings.
Based on these findings, it is recommended that most adult patients withthe common forms of retinitis pigmentosa take a supplement of 15,000 IU ofvitamin A daily under the supervision of their eye care professional and avoiduse of high-dose supplements of vitamin E. In the context of this treatment,a beta-carotene supplement is not a suitable substitute for vitaminA in the palmitate form.
A single capsule containing 15,000 IU of vitamin A in the palmitate formwill 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 nogreater benefit. Therefore, patients should not take vitamin A supplementsgreater that the 15,000 IU used in this study nor should they modify theirdiet to select foods with high levels of vitamin A. It should also be notedthat a total daily intake of greater than 25,000 IU of vitamin A daily hasbeen 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 vitaminA. Since patients under age 18 were not evaluated in this study, no formalrecommendation can be made for patients with retinitis pigmentosa under thisage.
A more comprehensive description of this study and its results are publishedin the June issue of the Archives of Ophthalmology to which you arereferred.
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.