Randomized Trial of DHA for Retinitis Pigmentosa Patients Receiving Vitamin A


Carol Weigel DiFranco

Status and phase

Phase 3


Retinitis Pigmentosa


Dietary Supplement: Vitamin A
Dietary Supplement: Docosahexaenoic acid
Dietary Supplement: Control fatty acid

Study type


Funder types




Details and patient eligibility


The purpose of this trial is to determine whether a nutritional supplement in addition to vitamin A will slow the course of retinitis pigmentosa.

Full description

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 either 1200 mg/d of docosahexaenoic acid or control capsules. 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.


221 patients




18 to 55 years old


Accepts Healthy Volunteers

Inclusion criteria

Ocular Criteria:

Retinitis Pigmentosa, typical (non-syndromic) forms Best corrected visual acuity Greater than or equal to (GE )20/100 HFA 30-2 total point score GE 250 dB (decibels) 30 (Hertz) Hz ERG cone amplitude GE 0.68 microvolts

Dietary Criteria:

Dark fish intake Less than or equal to (LE) five servings per week Dietary omega-3 fatty acid intake LE 0.41 g/d Preformed Vitamin A intake in diet and supplements LE 10,000 IU/d Supplement intake LE 5000 IU/d of Vitamin A and LE 30 IU/d Vitamin E Consumption LE 3 alcoholic beverages per day

Medical and other criteria:

Body Mass Index Less than (LT )40 and weight GE 5th percentile for age, sex, and height Serum retinol level LE 100 mg/dl and serum retinyl ester levels LE 380 nm/L Serum cholesterol level LT 300 mg/dL and serum triglyceride levels LT 400 mg/dL Agree not to know study capsule content

Exclusion criteria

Ocular criteria:

No confounding ocular disease

Dietary criteria:

No intake of cod liver oil or omega-3 capsules

Medical and other criteria:

Not pregnant or planning to become pregnant No clinically significant abnormal result on Complete Blood Count or serum liver function profile No other disease which might affect absorption or metabolism of DHA or Vitamin A

Trial design

Primary purpose




Interventional model

Parallel Assignment


Quadruple Blind

221 participants in 2 patient groups, including a placebo group

Docosahexaenoic acid + Vitamin A
Experimental group
Participants randomized to this arm received 1200 mg/d docosahexaenoic acid and 15000 IU/d Vitamin A as retinyl palmitate
Dietary Supplement: Docosahexaenoic acid
Dietary Supplement: Vitamin A
Control fatty acid + Vitamin A
Placebo Comparator group
Patients randomized to this arm received 500 mg/d of fatty acid with no docosahexaenoic acid and 15000 IU/ Vitamin A as retinyl palmitate
Dietary Supplement: Control fatty acid
Dietary Supplement: Vitamin A

Trial contacts and locations



Data sourced from clinicaltrials.gov

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