The Effect of Transcorneal Electrical Stimulation on the Electroretinogram in Patients with Retinitis Pigmentosa

Abstract

Retinitis Pigmentosa (RP) is a progressive and degrading illness impairing the vision of all age groups [1-3]. The disease is caused by mutations which are affecting the photoreceptors and the retinal pigment epithelium (RPE) [1, 4-6]. RP can be monitored by electroretinogram (ERG), it is an objective method which measures the remaining function of the photoreceptors [3]. A pilot study performed by Schatz, A., et al in 2011 showed an increase in visual field in patients with RP when treated with TES. [7]. A follow up study with the primary outcome of efficacy is ongoing in Tübingen, Germany (EST2). To investigate the safety of TES an open label multicenter safety study was initiated. The study “Transcorneal electrical stimulation for treatment of Retinitis pigmentosa – TESOLA” includes 100 patients. Ten of the patients were treated in Norway, at OUS Ullevål under the supervision of Professor Ragnheiður Bragadóttir and Dr Josephine Prener Holtan. The patients were included according to study protocol and followed up with controls every 3 months. The treatment lasted six months and measurements of ERGs were done to investigate possible effects by TES. The ERG is an objective diagnostic tool used to confirm visual function for the diagnosis of hereditary retinal disorders, such as RP [3]. Patients with RP will have reduced and delayed photoreceptor responses due to decreased sensitivity to light [2, 3]. There are over hundred different genetic mutations that cause RP. The mutations cause degeneration of the photoreceptors affecting the metabolic pathways in the different cell layers in the retina. Earlier studies have shown how TES possibly can slow the course of RP by increasing the production of neurotrophic factors in the eye [8-10].