Transcorneal Electrical Stimulation in Patients with Retinal Artery Occlusion: A Prospective, Randomized, Sham-Controlled Pilot Study

Abstract

IntroductionThe purpose of this study was to investigate the safety and efficacy of transcorneal electrical stimulation (TES) in patients suffering from retinal artery occlusion (RAO).MethodsTwelve 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.ResultsTES 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/m2; P = 0.03) in the 150% treatment group. All other parameters in all other groups remained statistically unchanged.ConclusionsAlthough 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.

Electrical Stimulation as a Means for Improving Vision

“…44 Naycheva et al 43 demonstrated that the slopes of the scotopic a-waves significantly increased in patients with central or branch retinal artery occlusion. TES treatment performed >4 months after the onset of nonarteritic ischemic optic neuropathy exhibited improved visual acuity in two of three eyes examined.…”

“…Other clinical TES studies reported slight corneal superficial punctuate keratopathy, 41 transient superficial keratitis, 39 and foreignbody sensations in three patients. 43 Adverse effects after TES in animal studies have not been reported; however, one study addressed this concern and reported no negative effects up to 35 hours after application. 34 All other methods will, by nature of their invasiveness, be prone to various complications, depending on the location.…”

The Efficacy of Transcorneal Electrical Stimulation for the Treatment of Primary Open-angle Glaucoma: A Pilot Study

“…Shatz et al demonstrated that latencies and amplitudes on ERG in patients with retinitis pigmentosa during TES treatment did not change significantly, 11 and Naycheva et al also reported similar results in RAO subjects before and after TES. 8 However, some researchers have reported improved mfERG responses. Oono et al reported significant reductions in N1 and P1 latency after TES in subjects with RAO, although the N1 and P1 amplitudes did not change significantly.…”

“…5 In clinical studies, TES has been shown to improve visual acuity (VA) and/or VF in patients with various neuroretinal diseases, including retinal artery occlusion (RAO), nonarteritic ischemic optic neuropathy, Best vitelliform macular dystrophy, and traumatic optic neuropathy. [6][7][8][9][10] TES also leads to improved electroretinography (ERG) findings and VF in patients with retinitis pigmentosa. 11 To date, however, no information is available concerning the long-term therapeutic effects of TES on glaucoma.…”

Electrical stimulation — a therapeutic strategy for retinal and optic nerve disease?

“…Inomata treated three patients with longstanding retinal artery occlusion, and found benefits in visual acuity and visual field area [22], and Oono has detected amelioration of multifocal ERG parameters and visual field parameters in his series of eight patients with fresh or longstanding branch retinal artery occlusion (RAO) [23]. Controlled, randomized and partially blinded short-term studies are available for RAO [24] and Stargardt's disease [25]: 12 patients in each study were divided into three subgroups according to stimulation strength in relation to the individual phosphene threshold (0%, 66%, or 150%). After a 6-week period of weekly stimulation, a small but statistically not significant positive trend was seen in the 150% group.…”