The purpose of this trial is to determine whether a nutritional supplement in addition to
vitamin A will slow the course of retinitis pigmentosa.
Retinitis pigmentosa (RP) is a group of inherited retinal degenerations with a worldwide
prevalence of approximately 1 in 4,000. Patients typically report night blindness and
difficulty with midperipheral visual field in adolescence. As the condition progresses,
they lose far peripheral visual field. Most patients have reductions in central vision by
age 50 to 80 years. Based on electroretinograms (ERGs), the course of the disease can be
slowed on average among adults on 15,000 IU/day of vitamin A palmitate. While conducting
the trial on the effects of vitamin A on RP, it became apparent that another substance in
the diet could be affecting the course of the disease. This prompted the present
randomized, controlled trial.
This study is a randomized, controlled, double-masked trial with a planned duration of 5
years. Patients with the common forms of RP are assigned to either a test or a control
group. All receive 15,000 IU/day of vitamin A palmitate in addition to the capsules under
study. Participants will not know the contents of the supplement or the group to which they
have been assigned until the end of the trial. The main outcome measurement is the total
point score on the Humphrey Field Analyzer (HFA). In addition, computer-averaged 30-Hz cone
ERG amplitudes and visual acuity are measured annually.
Eligible patients must:
- Be between the ages of 18 and 56
- Be able to see the entire face of someone sitting across the table from them without
- Read newspaper-size print without special magnifying aids
- Walk unaided in daylight
- Have a normal fasting serum vitamin A and normal liver function profile
- Be in good general health
- Reside in the United States
- Women who are pregnant or planning to become pregnant cannot be included because of
the risk of birth defects that could occur while they are on a vitamin A supplement.
Eliot Berson, MD
Berman-Gund Laboratory for the Study of Retinal Degenerations, Harvard Medical School