In vivo measurement of retinal neurovascular changes with transcorneal electrical stimulation using optical coherence tomography

Transcorneal electrical stimulation (TES), which as a noninvasive approach of retinal electrical stimulation, can activate releasing of neurotrophic factors and regenerate injured retinal neurons, has become a potential therapeutic method for retinal diseases. However, the mechanism of TES on the regeneration of retinal neurons has not been completely determined. The purpose of this study was to explore how the depth-resolved intrinsic optical signals (IOSs) and blood flow in cat retina change with TES. In the experiments, the cat retinae were imaged by our custom-designed spectral-domain OCT with a central wavelength of 840nm. OCT scanning and TES were synchronized so as to record images of retina at pre-, during and post-stimulation period, respectively. In each period, the IOSs were then extracted in structure images by registration and segmentation algorithms. And the blood flow was extracted in phase contrast images derived by phase-resolved Doppler OCT method including bulk motion compensation and phase unwrapping. Based on our preliminary results on 5 eyes of 4 cats, we found a significant increase of both positive and negative IOSs in each layer during and after TES compared to those of pre-stimulation and sham stimulation, while the changes of average blood flow before, during and 6 seconds after TES were not obvious. The preliminary results provide experimental data of neurovascular alterations under TES, which will benefit the study of the therapeutic mechanism of TES. But complete understanding of neurovascular response to TES should be further investigated.