Randomized Trial of Vitamin A and Vitamin E Supplementation for Retinitis Pigmentosa
Vitamin E
+ Vitamin A
Retinitis Pigmentosa
See all eligibility criteria
Treatment Study
See protocol details
Summary
To determine whether supplements of vitamin A or vitamin E alone or in combination affect the course of retinitis pigmentosa. Retinitis pigmentosa (RP) is a group of inherited retinal degenerations with a worldwide prevalence of about 1 in 4,000. Patients typically report night blindness in adolescence and lose vision in the midperipheral followed by far-peripheral visual field in adulthood due to progressive loss of both rod and cone function. Most patients have reductions in central vision by age 50 to 80 years. Modern-day electroretinograms (ERGs) make it possible to record retinal responses from most patients with remaining vision and thereby monitor objectively the course of their disease. While the natural course of retinal degeneration in the common forms of RP was being studied, it was noted that a subgroup of patients aged 18 through 49 who were treating themselves with both vitamin A and vitamin E and other nutritional supplements exhibited less decline in ERG amplitude over a 2-year period. These preliminary findings, as well as the known roles of vitamins A and E in maintaining normal photoreceptor function and structure, prompted this randomized, controlled trial to determine whether these vitamins alone or in combination would halt or slow the progression of the common forms of RP. This study was a randomized, controlled double-masked trial with 2 x 2 factorial design and duration of 4 to 6 years. Patients were assigned to one of four treatment groups: 15,000 IU/day vitamin A 15,000 IU/day vitamin A + 400 IU/day vitamin E trace amounts of both vitamins A and E 400 IU/day of vitamin E The main outcome measure was the 30-Hz cone ERG amplitude. In addition, visual field and visual acuity were measured annually.
Protocol
This section provides details of the study plan, including how the study is designed and what the study is measuring.In this clinical study, participants are placed into groups randomly, like flipping a coin. This ensures that the study is fair and unbiased, making the results more reliable. By assigning participants by chance, researchers can better compare treatments without external influences.
Other Ways to Assign Participants
Non-randomized allocation: Participants are assigned based on specific factors, such as their medical condition or a doctor's decision.
None (Single-arm trial): If the study has only one group, all participants receive the same treatment, and no allocation is needed.
Participants receive different combinations of treatments to see how they work together. This approach helps researchers determine whether a combination of treatments is more effective than a single treatment alone.
Other Ways to Assign Treatments
Single-group assignment: Everyone gets the same treatment.
Parallel assignment: Participants are split into separate groups, each receiving a different treatment.
Cross-over assignment: Participants switch between treatments during the study.
Sequential assignment: Participants receive treatments one after another in a specific order, possibly based on individual responses.
Other assignment: Treatment assignment does not follow a standard or predefined design.
Neither participants nor researchers know who is receiving which treatment. This is the most rigorous way to reduce bias, ensuring that expectations do not influence the results.
Other Ways to Mask Information
Open-label: Everyone knows which treatment is being given.
Single-blind: Participants do not know which treatment they are receiving, but researchers do.
Triple-blind: Participants, researchers, and outcome assessors do not know which treatment is given.
Quadruple-blind: Participants, researchers, outcome assessors, and care providers all do not know which treatment is given.
Eligibility
Researchers look for people who fit a certain description, called eligibility criteria: person's general health condition or prior treatments.Conditions
Criteria
