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D.G. Birch, K.G. Locke, D.H. Wheaton, G.E. Fish, D.R. Hoffman; Dietary Nutrients and Yearly Rates of Decline in Retinal Function in Patients with X-linked Retinitis Pigmentosa (XLRP) . Invest. Ophthalmol. Vis. Sci. 2003;44(13):545.
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Purpose: A growing body of evidence suggests that Vitamin A (Vit A), Vitamin E (Vit E) and docosahexaenoic acid (DHA) can influence the rate of progression of retinitis pigmentosa (RP). Vit A has been shown to slow the rate of ERG decline, while Vit E may accelerate progression. DHA deficiency, which is common in XLRP, is associated with ERG deficits in both humans and animals. The purpose of the present study was to relate measures of retinal degeneration to DHA, Vit A and Vit E levels in XLRP. Methods: Male patients (n=44; mean age = 16 yr) received either DHA (400 mg/day) or placebo as part of a 4-year, double-blind, randomized clinical trial. All patients were provided a summary of the previous randomized trial of Vit A and Vit E supplementation (Berson et. al, 1993) but no attempt was made to influence the choice of supplements. By report, 15/44 patients took a daily multivitamin. Red blood cell (RBC) DHA mass concentration along with Vit A and E plasma concentrations were measured annually. Visual function tests were obtained on two separate days each year and included ETDRS acuity, visual activities questionnaire (VAQ), dark-adapted (DA) thresholds, static (Humphrey) perimetry and full-field ERGs. Fundus photos including eight 60° standard fields were obtained each year and scored for change by masked examiners at the end of the trial. Results: Mean RBC-DHA mass (yrs 1-4) was inversely correlated with annual loss of cone ERG amplitude (r = -0.38; p = 0.01). One half of patients (22) had rod ERG responses at baseline. The inverse correlation between mean RBC-DHA mass and annual loss of rod ERG amplitude was borderline (r = -0.36; p=0.1). Mean DHA mass was inversely correlated with change in fundus appearance between Years 0 and 4 (r = -0.42; p = 0.005). No relationships were found between DHA mass and acuity, VAQ, DA, or visual field. Plasma Vit A and E levels varied by less than a factor of three among patients and were not correlated with degree of change on any test. Conclusions: The results provide support for a beneficial role of DHA supplementation for slowing the functional ERG decline and pigmentary disturbances associated with XLRP.
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