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Subretinal Prosthesis Shows Promise in Rats

May allow vision to be restored in people with degenerative eye diseases

TUESDAY, May 15 (HealthDay News) -- Micron-sized solar panel-like devices implanted underneath the retina of rats can generate electrical signals and may allow vision to be restored in individuals with degenerative eye diseases, according to a study published online May 13 in Nature Photonics.

Keith Mathieson, Ph.D., from Stanford University in Palo Alto, Calif., and colleagues implanted a photovoltaic subretinal prosthesis, comprising silicon photodiodes in each pixel, which are connected to an activated iridium oxide film electrode, in healthy and degenerate rat retinas. They placed a multi-electrode array above the layer of ganglion cells to gauge the activity of the subretinal array. They then sent pulses of near infrared or visible light to each pixel using video goggles, and measured the electrical response.

The researchers found that healthy retinas were stimulated by both visible and near infrared light. The degenerate retinas from blind rats were stimulated only by near infrared light, and larger amounts of light were needed to achieve the same level of activity observed in the healthy retinas. The level of near infrared light needed was two orders of magnitude below the established ocular safety limit. Illuminating a single 70 µm bipolar pixel elicited neural responses.

"In conclusion, we demonstrate that near infrared light-induced photovoltaic stimulation using a subretinal photodiode array elicits bursts of retinal ganglion cell spikes in both healthy and degenerate rat retinas at irradiances substantially below ocular safety limits," Mathieson and colleagues write. "Such a fully integrated wireless implant promises the restoration of useful vision to patients blinded by degenerative retinal diseases."

Optobionics provided the artificial silicon retina samples for the study.

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