Transcorneal electrical stimulation increases chorioretinal blood flow in normal human subjects

Abstract

PurposeThe aim of this article is to investigate the effect of transcorneal electrical stimulation (TES) on chorioretinal blood flow in healthy human subjects.MethodsThe chorioretinal blood flow of 10 healthy subjects was measured before and after TES by laser speckle flowgraphy and expressed as the square blur rate (SBR). The chorioretinal blood flow was determined before and immediately after TES and 0.5, 1, 1.5, 2, 2.5, 3, 24, and 40 h after TES in three different areas: the margin of the optic disc, a point located midway between the optic disc and macula, and the macula area. The SBR of the stimulated eye is expressed relative to the value of the fellow eye. The mean standardized blur ratio was calculated as the ratio of the standardized SBR to the baseline SBR. The changes of intraocular pressure (IOP), blood pressure (BP), and pulse rate (PR) were determined after each measurement of the SBR. The ocular perfusion pressure (OPP) was calculated from BP and IOP.ResultsThe mean standardized blur ratio at the optic disc did not change significantly throughout the course of the experiment. However, the mean standardized blur ratio midway between the optic disc and macula and at the macula area were significantly higher after TES than that after sham stimulation at 3 and 24 h (P < 0.05, P < 0.01, respectively). At all times, the mean BP, PR, IOP, and OPP were not significantly different from the prestimulation values.ConclusionsTES increases the chorioretinal blood flow in normal subjects with minimal effects on the systemic blood circulation and the IOP. The increase in chorioretinal blood flow may be one of the beneficial effects that TES has on ischemic retinal diseases.

Electrical Stimulation as a Means for Improving Vision

“…47 It has been shown that TES (up to 150 mA, 20 Hz, 30 minutes, one session) increases choroidal blood flow in normally sighted patients, with minimal effects on the general blood circulation and intraocular pressure. 40 The authors suggested that this is probably an important mechanism that underlies the beneficial effects of TES in …”

“…62 TES also was found to improve choroidal blood flow in normal-sighted patients, with mild effects on the systemic blood circulation and intraocular pressure. 40 The expression of retinal genes and the levels of retinal proteins associated with TES have recently been investigated. Willmann et al 34 investigated the effect of TES on mRNA expression, retinal structure, and function.…”

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

“…Kurimoto et al reported that chorioretinal blood flow midway between the optic disc and the macula increased after TES in healthy human subjects. 21 The Leuven Eye Study showed that patients with OAG had lower blood velocities in the central retinal vessels than the controls did. 22 From these studies, we can hypothesize that TES has an effect on the retinal vessels and improves chorioretinal blood flow, which may improve RGC function.…”

Transcorneal Electrical Stimulation Shows Neuroprotective Effects in Retinas of Light-Exposed Rats

“…15 In animals, a protective effect of TES has been described for ischemic rat retinas by Wang et al 16 Moreover, Morimoto et al 17 have shown an increased survival of axotomized retinal ganglion cells, which has been confirmed by Okazaki et al 18 The effect of TES has been attributed to the release of neurotrophic factors, 5 such as an increased expression of insulin-like growth factor (IGF-1), [19][20][21] brain-derived neurotrophic factor (BDNF), 6,22,23 FGF2, 24 and B-cell lymphoma 2 protein. 25 Protective effects of TES have also been linked to the downregulation of pro-apoptotic factors, such as BAX and tumor necrosis factors, 25 which are involved in the apoptosis cascade of retinal cells.…”