In vivo acute and chronic evaluation of a nanowire based subretinal prosthesis

Abstract

Purpose : A nanowire based retinal prosthesis with a theoretical resolution of 20/80 has been developed with the aim of restoring useful vision to blind patients suffering from retinal degenerative diseases. This report presents the evaluation of tolerance and function of the device in vivo both acutely and after six months.

Methods : The retinal prosthesis devices were implanted into the subretinal space of Dutch pigmented rabbits (N=12) via a trans-scleral approach. Three screw electrodes were inserted over the visual cortex to record visual evoked potentials (VEPs) and electrically evoked potentials (EEPs). A Visual Diagnostic System with Ganzfeld dome (LKC Technologies) was used for electrophysiology recordings. A Benchtop Laser Controller (Thorlabs) delivered either 532 nm or 850 nm laser light to the implanted device. Two devices were left implanted for six months for chronic testing. The device activation signal was recorded from the cornea using an ERG electrode to assess functionality after six months of implantation. Histology of the retina surrounding the device was performed to evaluate the effect of chronic implantation.

Results : Control VEPs were elicited with bright full-field flashes, confirming the health of the eye post implantation. Focal VEPs from retina over the device were elicited with 3 mm spot size 532 nm green laser up to 100 μW/mm². EEPs were elicited with electrical stimulation by activating the subretinal prosthesis with 3 mm spot size 850 nm infrared laser up to 11 mW/mm², a wavelength which was confirmed undetectable by the photoreceptors. The devices implanted for six months were activated with pulsed IR light and the activation signals were readily recorded from the cornea using an ERG electrode. Histology showed that the retinal tissue surrounding the device showed no signs of inflammation or degradation after six months.

Conclusions : The prosthesis, powered only by pulsed laser light, effectively delivers electrical stimulation to the retina and generates neuronal activity in the rabbit visual cortex. In future experiments the nanowires will be biased with external power to increase the dynamic range of electrical stimulation and reduce the light intensity required to elicit a response. This study also showed that the device does not negatively affect surrounding retinal tissue and it continues to deliver electrical stimulation in vivo six months post implantation.

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