Transcorneal Electrical Stimulation (TES) results in a slowing of Visual Field (VF) progressive deterioration in Retinitis Pigmentosa (RP) patients

Abstract

Purpose: To perform an exploratory statistical analysis of the percentage of patients who show no change from baseline in the EST2 study (personal communication, Gekeler, et al, ARVO submission, 2015).<br />

Methods: A prospective randomized study was performed to confirm efficacy of TES in reducing the rate of VF loss in RP (EST2 study).<br /> Fifty two patients per protocol were treated with TES (using the OkuStim^®, Okuvision GmbH, Germany) weekly for 30 minutes for 52 weeks, prospectively randomized into 3 groups (sham, 150%(TES150) & 200%(TES200) of current that elicited a phosphene threshold. Octopus VF area using III4e & V4e stimuli were measured for each patient. <br /> The difference between VF-III4e and VF-V4e isopter area was also analyzed to better represent the periphery. An exact binomial test was used to test if there were significant change from expected value in each of the groups at each visit. <br /> A Fisher’s exact test was used to compare the percentage of patients with no change in VF-III4e, VF-V4e and the difference between VF-III4e and VF-V4e at each visit relative to sham.<br />

Results: The expected value of the percentage of patients with no change from baseline for an effective treatment is .50. Statistical significance relative to the expected value indicates that the treatment was not completely effective. Both sham and TES150 groups showed significance (p<.05) at multiple visits. The TES200 group showed a significant difference at only 1 of 4 visits.<br /> A statistical trend (p<.10) was observed at Week 52 for percentage of patients with no change from baseline in VFV4e for TES200 relative to the sham group. A statistically significant difference (p<.05) was observed between TES200 and sham at week 78 in the difference between VF-III4e and VF-V4e. <br />

Conclusions: Results indicate that TES at the 200% treatment level of phosphene threshold may reduce the rate of progression of RP. The significant difference observed relative to sham may indicate that the effect is the result of the preclinically well established release of growth factors induced by electrostimulation suggesting a neurotrophic effect to the peripheral retina.<br /> <br />