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Based on the findings reported recently in the Archives by Berson et al,1 the National Retinitis Pigmentosa Foundation and the RP Foundation Fighting Blindness have begun national campaigns that will probably persuade most patients with RP to begin a lifelong regimen of vitamin A supplementation. This media blitz was launched despite important and compelling uncertainties raised in an accompanying editorial by Massof and Finkelstein.2 The authors of this editorial discuss at length three reservations, including the use of an electrophysiologic parameter (ERG [electroretinogram] amplitude) to measure clinical impact.
We wish to raise an additional concern. In reality, Berson et al1 measured three variables—ERG amplitude, visual acuity, and visual fields. Had any one of these three shown a response to therapy, would they have interpreted this finding as a successful outcome? Furthermore, Berson et al measured clinical impact for two agents (vitamins A and E), and they performed
Gamel JW, Barr CC. A Randomized Trial of Vitamin A and Vitamin E Supplementation for Retinitis Pigmentosa. Arch Ophthalmol. 1993;111(11):1462-1463. doi:10.1001/archopht.1993.01090110018006