Abstract
Recent studies indicate therapeutic benefits of electrical stimulation in cases of specific ophthalmic diseases that are associated with dysfunctional ocular microcirculation. This suggests effects of electrical stimulation on vascular functions. In the present study, we investigated the effects of electrical stimulation on retinal vessel reactions using dynamic vessel analysis (DVA). Eighty healthy subjects were randomly assigned to one of three groups receiving electrical stimulation with different current intensities: 400 μA (n = 26); 800 μA (n = 27); 1200 μA (n = 27). The electrode montage for electrical stimulation consisted of a ring-shaped active electrode surrounding one eye and a square return electrode at the occiput. Rectangular, monophasic, positive current pulses were applied at 10 Hz for a duration of 60 s per stimulation period. DVA was used to observe the stimulation-induced reactions of retinal vessel diameters in response to different provocations. In three DVA measurements, three stimulus conditions were investigated: flicker light stimulation (FLS); electrical stimulation (ES); simultaneous electrical and flicker light stimulation (ES+FLS). Retinal vasodilation caused by these stimuli was compared using paired t-test. The subjects receiving electrical stimulation with 800 μA showed significantly increased retinal vasodilation for ES+FLS compared to FLS (p < 0.05). No significant differences in retinal vessel reactions were found between ES+FLS and FLS in the 400 and 1200 μA groups. No retinal vasodilation was observed for ES for all investigated current intensities. The results indicate that positive pulsed electrical stimulation of an adequate intensity enhances the flicker light-induced retinal vasodilation.
Highlights
This study investigated the behavior of retinal vessels in response to electrical stimulation using dynamic vessel analysis (DVA) for the first time
We observed a significant enhancement of retinal vasodilation to flickering light in the case of simultaneous electrical stimulation with positive current pulses of 800 μA
Sole electrical stimulation induced no immediate response of retinal vasculature since the retinal vessel diameter remained unaltered in this stimulus condition compared to baseline
Summary
Electrical stimulation of the eyes has demonstrated positive effects in patients suffering from ophthalmic diseases, such as retinitis pigmentosa (Schatz et al, 2011, 2017), age-related macular degeneration (Anastassiou et al, 2013; Chaikin et al, 2015), retinal artery occlusion (Inomata et al, 2007; Oono et al, 2011; Naycheva et al, 2013), and optic neuropathy (Gall et al, 2011, 2016; Sabel et al, 2011). The neuroprotective effects depend on the parameters of the electrical stimulation, such as intensity, duration, and waveform (Morimoto et al, 2010)
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