Interphase gaps can selectively contribute to enhance the response to cathodic-first electrical stimulation in retinal prosthesis

Abstract

Purpose : To investigate the effect of interphase gaps on the efficiency of electrical stimulation in retinal prosthesis.

Methods : Acute electrophysiological experiments were performed on retinal-degenerated rats [Royal College of Surgeons (RCS), n = 10], aged 20–24, anesthetized with urethane (1.75 g/kg). An anodic-first (AF) or a cathodic-first (CF) biphasic current pulse with various interphase gap (0–2.0 ms) was applied to the rats’ left eye through a stimulating electrode on the sclera. Evoked potentials (EPs) were recorded from the right superior colliculus. All procedures were in accordance with the Association for Research in Vision and Ophthalmology Statement for the Use of Animals in Ophthalmic and Vision Research. This study was approved by the Institutional Animal Care Committee of Nidek Co., Ltd.

Results : Addition of an interphase gap significantly increased the response to CF pulses (p < 0.05, paired t-test) in that longer interphase gaps led to larger EP amplitudes, closer to the amplitudes originated by anode pulse stimulation. On the contrary, such effect of interphase gaps on EP enhancement was less apparent in AF pulses stimulation.

Conclusions : The present study with degenerated retinas suggests that increased retinal response to electrical stimulation can be obtained by an interphase gap inserted into CF pulses.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.

 

Fig. 1. Comparison of average EPs amplitude between biphasic pulses with interphase gap and monophasic pulses. (a) AF, (b) CF. The black cross bars (-) represent the mean values, and the circle (o) represents individual values. The lines connecting the symbols (o) indicate that the data are from the same individual. RCS (n = 10). A paired t-test was performed to compare the effect of different interphase gap durations = 0. * p < 0.05, ** p < 0.01.