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Dennis R Hoffman, Dianna K H Wheaton, Rand Spencer, Gary Fish, N Shirlene Pearson, Yi-Zhong Wang, Martin Klein, Alison Takacs, Kirsten G Locke, David G Birch; Ancillary Outcomes of the DHAX Trial: Docosahexaenoic Acid (DHA) Supplementation in X-Linked Retinitis Pigmentosa (XLRP). Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):3803.
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In a 4-year randomized, controlled trial of DHA supplementation to patients with XLRP, primary and secondary ERG outcomes were not significantly different between supplemented and placebo groups (Hoffman et al. JAMA Oph. 2014). Herein, we examine efficacy of DHA supplementation on ancillary outcomes in the DHAX Trial.
The per protocol cohort consisted of fully compliant males diagnosed with XLRP (mean age 15.2 yr; range=7-31 yr) and randomized to 30 mg DHA/kg/day (n=29) or placebo (n=22). All participants received a multi-vitamin to minimize lipid peroxidation. Outcomes measured annually included visual acuity (eETDRS), shape discrimination hyperacuity (SDH), final dark-adapted thresholds (Goldmann-Weekers), fundus appearance (4-year progression evaluated by masked scoring of fundus photographs; Canon CF6000), and foveal (<3o), macular (3o-10o), and peripheral (10o-60o) visual field sensitivities (VFS) obtained with Humphrey perimeter (30-2 & 60-2); values were summed post hoc to give total VFS. DHA in red blood cell (RBC) total lipids was determined every 6 mo. Repeated measures mixed-model regression analysis and t-tests were used to assess efficacy.
Oral DHA supplementation for 4 years increased mean RBC-DHA levels by 3.2-fold (p<0.00001). Placebo and DHA-supplemented groups did not differ in progression of visual acuity (OD & OS avg; p=0.17), SDH (OD & OS avg; p=0.13), or fundus appearance (p=0.70). A trend toward benefit to final dark-adapted thresholds (p=0.06) was found in the supplemented group. The yearly decrease in foveal VFS was less in DHA (0.15%) vs. placebo participants (1.4%; p=0.039). Similarly, the yearly rates of progression in macular, peripheral and total VFS were significantly reduced in the DHA-supplemented group vs. placebo (1.4% vs 3.2%, 4.8% vs 7.9%, and 4.4% vs 7.5%; p=0.031, p<0.00001, and p<0.00001). With change in RBC-DHA as the independent variable, mixed model analysis of the per protocol cohort showed that the rates of peripheral and total VFS decline were dependent on RBC-DHA change (p<0.0001).
High dose DHA supplementation significantly elevated blood DHA levels, was effective in slowing visual field loss, and showed a beneficial trend in final dark-adapted thresholds. However, DHA supplementation was not effective in slowing the loss of cone ERGs, rod ERGs, visual acuity, SDH, or fundus appearance.
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