Abstract
Purpose :
The theoretical visual acuity offered by retinal prostheses is limited by the use of implantable pulse generators and feedlines on the array. In parallel, the visual angle restored by most prostheses is limited to at best 20 degrees, primarily by reason of low conformability materials and subretinal placement. The combination of these limitations prevents implanted blind patients to benefit from artificial vision in their day-to-day life, as navigation in complex spaces and most of the daily visually-guided manipulation activities require both visual acuity and visual field together.
Methods :
Conjugated polymers allow for photovoltaic retinal stimulation with flexible and large arrays, thus opening the possibility for wide-field and high-density arrays freed from external power generator. In this work, we designed a photovoltaic epiretinal implant embedding 10’498 physically and electrically independent miniaturised photovoltaic pixels. Such implant combines a large visual angle, thanks to the flexibility of the organic materials used, and a high pixel density, possible through the patterning of the organic polymer films. Using single-pixel stimulation, minimum separable and grating visual acuity paradigms, we evaluated the spatial resolution of the prosthetic response elicited by this high-density photovoltaic implant in explanted retinal degeneration 10 mouse retinas.
Results :
Each of the discrete photovoltaic pixels could elicit reproducible network-mediated response in light-insensitive retinal ganglion cells from 80 μW.mm-2. Moreover, the high-density arrangement of the pixels allowed retinal ganglion cells to be stimulated with a 0.3-degree resolution, what corresponds to a 20/480 visual acuity. During both two-points discrimination test and decreasing gratings tests, retinal ganglion cells exhibited desensitized response to repeated stimulation patterns, but marked response to pattern reversals. Such response resolution was observed in ganglion cells whose receptive field diameter exceeded the pixel pitch, suggesting that spatial discrimination can be achieved at the inner retinal level with epiretinal network-mediated stimulation.
Conclusions :
In view of the large visual angle (43°) covered by the photovoltaic epiretinal implant, this device could provide artificial vision with high peripheral resolution to retinitis pigmentosa patients, a valuable improvement for obstacle recognition, ambulation, and independence.
This is a 2021 ARVO Annual Meeting abstract.