Transcorneal electrical stimulation in patients with retinal artery occlusion: a prospective, randomized, sham-controlled pilot study

Abstract

Introduction: The purpose of this study was to investigate the safety and efficacy of transcorneal electrical stimulation (TES) in patients suffering from retinal artery occlusion (RAO).

Methods: Twelve patients with central and one patient with branch RAO (age 25-84 years, median 74 years) were enrolled in this prospective, randomized, sham-controlled study. RAO was diagnosed 10 days to 17 months prior to study participation. Patients were treated with TES (5 ms positive followed by 5 ms negative biphasic pulses at 20 Hz; applied with DTL electrodes) for 30 min once a week for 6 consecutive weeks. Patients were randomly assigned to TES with 0 mA (sham, n = 3), 66% (n = 5) or 150% (n = 5) of the patient's individual electrical phosphene threshold (EPT) at 20 Hz. Best corrected visual acuity, ophthalmology examination and EPT (at 3, 6, 9, 20, 40, 60, and 80 Hz) were determined at baseline and at eight follow-up visits over 17 weeks. During four visits (week 1, 5, 9, and 17) kinetic and static visual fields as well as full-field and multifocal electroretinography were measured. The method of restricted maximum likelihood (P < 0.05, Tukey-Kramer) was used to estimate the development of parameters under treatment.

Results: TES was tolerated well; no ocular or systemic adverse events were observed except for foreign-body sensation after TES (n = 3). During the study period the slopes of the scotopic a-wave increased significantly (high-intensity flash white 10 cd.s/m(2); P = 0.03) in the 150% treatment group. All other parameters in all other groups remained statistically unchanged.

Conclusions: Although TES was tolerated well, statistically significant improvements were found only for specific a-wave slopes. This is in contradiction to previous smaller, uncontrolled reports. Further studies with larger sample sizes and longer duration might, however, show additional significant effects.

Fig. 1

Transcorneal electrical stimulation was performed using a a sterile single-use DTL electrode and b a commercially-available neurostimulator programmed with c biphasic current pulses of 10 ms duration (5 ms positive, directly followed by 5 ms negative) at a frequency of 20 Hz

Fig. 2

Fundus photographs and development of visual field (VF) area in two selected patients from the group treated with 150% of the individual electric phosphene threshold at 20 Hz. In the treated patients, an enlargement of VF area was observed, but statistical significance was not reached. Retinal artery occlusion was diagnosed in patient 1 (left) at approximately 7 months and in patient 2 (right) at approximately 6 months prior to study enrollment. LE right eye, RE right eye