—In the article1 discussed by Dr Marmor, we demonstrated, in 235 patients with typical RP and no evidence of visual acuity-limiting cataract or macular edema, that for patients with visual fields smaller than 30°, the prevalence of decreased visual acuity increases with the extent of further visual field loss. Specifically, until the V-4-e visual field reaches 30°, 96% of patients retained 20/40 visual acuity or better. Fewer than one third of patients with visual fields smaller than 10° radius had visual acuities of 20/40 or better and intermediate percentages of patients with 20/40 visual acuity or better were seen at intermediate visual field sizes. In other studies,2,3 we showed that visual field loss in RP, regardless of subtype, progresses at a very predictable rate, following an exponential decay function.We appreciate Dr Marmor's interest in our work and are grateful for the opportunity to clarify
Madreperla S, Palmer R, Massof R, Finkelstein D. Visual Acuity and Field Loss in Retinitis Pigmentosa-Reply. Arch Ophthalmol. 1991;109(1):13–14. doi:10.1001/archopht.1991.01080010015007
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