Retinal vessel oximetry as a sensitive metabolic monitoring method for transcorneal electrical stimulation in retinitis pigmentosa

Abstract

AbstractBackgroundTranscorneal electrical stimulation (TES; OkuStim®) is a novel therapy method for patients with retinitis pigmentosa (RP). With progression of RP, loss of photoreceptors leads to less oxygen consumption and lower demand in the inner retina. Retinal oximetry (RO) as a non‐invasive method to analyze oxygen saturation in retinal vessels promises to be a useful therapy monitoring tool. The aim of our study was to compare the RO parameters at baseline and following TES.MethodsA total of 43 eyes of 22 subjects (11♀ 11♂) suffering from RP were examined. Stimulation was performed for 30 minutes weekly at 200% of the individual phosphene threshold on both eyes. The oxygen saturation was examined at baseline (BL), 1 week and 6 months after TES stimulation with the oxygen saturation tool of the Retinal Vessel Analyser (IMEDOS Systems UG, Germany). The global oxygen saturations, within 1.0–1.5 optic disc diameters from the disc margin, in retinal arterioles (A‐SO2; %) and venules (V‐SO2; %) were estimated and their difference (A‐V SO2; %) was calculated. In addition, we evaluated the diameters in the corresponding arterioles (D‐A; μm) and venules (D‐V; μm). ANOVA‐based linear mixed‐effects models were calculated with SPSS®.ResultsSix months after TES the A‐SO2 showed a tendency to increase (from 96.48 ± 12.27% to 100.15 ± 5.56%, p = 0.09), while the V‐SO2 showed a slight decrease (from 61.61 ± 12.78% to 59.79 ± 11.15%, p = 0.48). The A‐V SO2, which represents the oxygen consumption of the retina, showed a significant increase from 34.87 ± 9.38% at BL to 41.36 ± 9.18% after 6 months (p = 0.02). TES had no influence on the D‐A and D‐V (p > 0.6).ConclusionThese data indicate that TES therapy in RP leads to an increased oxygen consumption of the retina. Thus, RO proves to serve as a sensitive monitoring method for TES therapy in RP patients.