Characteristics and possible visual consequences of photopsias as vision measures are reduced in retinitis pigmentosa

Purpose. This study explored whether the location of photopsias (spontaneous phosphenes) in retinitis pigmentosa (RP) is related to the severity of vision loss, as has been suggested. Methods. Thirty-two RP subjects self-completed an online survey about photopsias, approximately 1 to 2 months after ETDRS visual acuity (VA), Pelli-Robson contrast sensitivity (CS), and Goldmann visual field (VF) measures were obtained. Results. The odds of noting photopsias only or mostly in areas of vision increased as vision was reduced across subjects, by 56% for every 0.1 logMAR VA (95% CI, 1.04-2.33; P = 0.03), 22% for every 0.1 logCS (95% CI, 1.02-1.46; P = 0.03), and 40% for every 1 unit logVF diameter (95% CI, 0.99-1.98; P = 0.06). The odds of noting photopias only in the periphery were reduced by 20% for every 0.1 logCS reduction (95% CI, 0.64-1.02; P = 0.066), and 18% for every 1 unit logVF diameter reduction (95% CI, 0.67-1.001; P = 0.051). For every 0.1 logMAR VA reduction, the odds of indicating that photopsias were located across a larger area over time were 30% greater (95% CI, 1.002-1.70; P = 0.048). The odds of being more aware of photopsias over time were increased as vision was reduced by 48% for every 0.1 logMAR VA (95% CI, 1.04-2.11; P = 0.03) and 18% for every 0.1 logCS (95% CI, 1.01-1.38; P = 0.04). The odds of reporting that photopsias interfere with vision were significantly greater when the photopsias occurred daily, more frequently, or across larger areas over time. Conclusions. These cross-sectional data indicate that in later RP stages, photopsias located more centrally, over larger regions, in areas with vision, and/or observed more frequently may obstruct vision at times and are a potential hindrance for patients' functioning or when obtaining vision measures.