Investigating the Effect of Vitamin A Supplementation on Retinitis Pigmentosa
Status:
Completed
Trial end date:
2009-05-06
Target enrollment:
Participant gender:
Summary
Retinitis pigmentosa (RP) is a collective term for a group of inherited retinal dystrophies
that are a major cause of irreversible blindness. RP of some type occurs in approximately 1
out of 3500 persons in the United States(1). Gene mutations are responsible for the majority
of RP. To date, mutations have been identified in 30 different genes linked to RP(2). The
visual prognosis of RP is poor, since the gradual but relentless visual field loss leads
eventually to some degree of blindness(3). Although no effective treatment for RP has been
identified, participants supplemented with a daily oral dose of 15,000 IU vitamin A palmitate
have shown, on average, a slower rate of deterioration of retinal function when the
intervention is continued over several years(4). The purpose of this research is to determine
whether administration of high oral doses of vitamin A can acutely improve cone photoreceptor
function in RP participants as measured by electroretinography (ERG). In this interventional,
non-randomized, prospective, pilot study, 5 participants will receive a daily oral dose of
50,000 IU of vitamin A palmitate for 4 weeks, followed by a maintenance dose of 15,000 IU
daily for the subsequent 2 weeks. The primary efficacy outcome is a relative percentage
change in ERG response amplitude subsequent to vitamin A supplementation. A secondary
efficacy outcome is a relative percentage change in implicit time from pre- to post- vitamin
A supplementation, with improvement specified as a shorter response implicit time. Other
secondary outcomes will be improvements in visual field (Humphery, 10-2; sum of thresholds).
Safety outcomes include visual fields, ETDRS visual acuity, intraocular pressure, serum
vitamin A level and liver function tests.