Cortical recordings of acute epiretinal stimulation with the VLARS-device in rabbits

Abstract

Purpose : The VLARS (Very Large Array Retinal Stimulator) is an epiretinal stimulator designed to conquer degenerative retinal diseases, such as Retinitis pigmentosa. The stimulators diameter of ca. 12mm enables a wide area of stimulation with its 250 iridium-oxide sputtered gold electrodes. Thus, not only restoring the acuity of the central vision but also regaining a peripheral visual field seems feasible. In order to proof the principal of stimulating distant areas of the retina we simultaniously recorded the elicited potentials in the visual cortex of rabbits in an acute setting.

Methods : Six rabbits were succesfully implanted with the VLARS device mounting 25 active electrodes placed in clusters on the star shaped device. Ten Electrodes were placed in high density in the center of the device, and 5 each at three peripheral positions. Prior to implanting the VLARS device a recording electrode, capable of recording with 32 electrodes rostro-caudally and in depth, was positioned in the visual cortex of the rabbits. As reference, field potential changes after LED flashes were recorded. For the acute stimulation single electrodes and cluster stimulation with up to five electrodes with currents between 50µA and 120µA per electrode were applied. As a stimulation pattern negative first for 200µs, followed by 200µs positive charge and an intermission of 5ms between the stimulations was used.

Results : The recorded results show that stimulating at distant positions on the retina elicits different field potential changes corresponding to the expected retinotopy of the rabbit's eye. The currents used for stimulation were within the thresholds of the device and did not exceed stimulation currents from other non-harmful epiretinal stimulation experiments. Even though the results were particularly convincing in two animals, the results varried greatly with the success of the implantation surgery, and the stability of the set up during the acute experiment.

Conclusions : The acute epiretinal stimulations and cortical recordings demonstrate that the VLARS device is capable of covering a large area of perception, as well as being able to stimulate meaningful in the center of the visual field. Thus both the acuitiy of central vision and the periphery are addressed by one implanted device.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.