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Eric A Pierce, Kinga Maria Bujakowska, Emily Place, Daniel Navarro-Gomez, Matthew Maher, Carol Weigel-DFranco, Jason Comander; The Effect Of Vitamin A On Progression Of Retinitis Pigmentosa Is Not Determined By The Underlying Genetic Cause Of Disease. Invest. Ophthalmol. Vis. Sci. 2017;58(8):2011.
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Three clinical trials were performed between 1984 and 2008 to test the hypothesis that vitamin A supplementation alone or in combination with DHA or lutein can slow the rate of progression of retinal degeneration for patients with retinitis pigmentosa (RP). The results of these trials showed that on average, patients taking 15,000 IU of vitamin A per day experienced slower decline in 30 Hz electroretinogram (ERG) response amplitudes than controls (Berson et al Arch Ophthalmol 130: 707, 2012). The goal of this study was to ask if patients with different genetic forms of RP respond to vitamin A supplementation differently.
330 subjects were identified who participated in one or more of the three vitamin A clinical trials, and who had sufficient 30Hz ERG amplitudes to avoid floor artifacts. We performed panel-based genetic testing for subjects who did not have genetic diagnoses from prior studies. Robust linear regression and mixed regression models were used to construct exponential rate of decay estimates for each subject, grouped by gene and vitamin A treatment status.
189 subjects with genetic diagnoses were available for analyses, including 126 in the vitamin A treated group, and 63 in the control group. 47 had mutations in USH2A, 35 in RHO, 28 in RPGR, 11 in PRPF31, and 8 in PRPH2. The rate of loss of retinal function of subjects with USH2A mutations was faster than that in other genotypes (p<0.0001), and slower with PRPH2 mutations (p=0.04). Subjects with RHO-associated RP (N=35) who took vitamin A did not have a significantly slower rate of decline of 30Hz amplitude than controls (-8.3% vs -7.6%/year, p>0.05). Vitamin A supplementation appeared to reduce the rate of decline in retinal function for subjects with PRPH2-associated RP: -3.8%/yr in controls (N=5) versus +2.1%/yr in the vitamin A group (N=3), p=0.007.
The treatment effect of vitamin A did not appear to be concentrated in patients with specific genetic causes of disease. One small genetic subgroup of patients with PRPH2-associated RP showed a larger than average vitamin A treatment effect, but this finding was based on a small number of subjects. These data suggest that the previously observed benefit of vitamin A supplementation for adults with typical RP applies broadly for patients with different genetic forms of disease, within the limits of the sample sizes evaluated.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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