Functional retinal prosthesis created from organic materials

An organic retinal prosthesis has restored light perception in blind rats with retinitis pigmentosa (RP), suggesting that restoring sight in humans may soon be possible without the complex hardware required for today’s devices.

The research team from the Italian Institute of Technology in Genoa combined an organic semiconductor, which has photovoltaic properties in ambient light conditions, with a conductive polymer to pass the generated electrical charge to the eye’s nerve cells. Both are layered atop a silk substrate that allows the implant to heal onto the retina.

"We hope to replicate in humans the excellent results obtained in animal models," said lead researcher Grazia Pertile, MD.

In a study published this week in Nature Materials, the team showed that rats exhibited signs of light-sensitivity for as long as 6 to 10 months after implantation.

After receiving the prostheses, the RP rats displayed pupillary light reflexes close to that of normal rats at as low as 4 lux, which is comparable to the ambient light outside at twilight. Positron emission tomography imaging of the rats’ brains also demonstrated increases in basal metabolic activity within the primary visual cortex.

How the electrical charges from the photovoltaic molecules are converted into nerve signals remains unknown. Another limitation is the inability to quantify the degree of sight restoration in an animal model.

Nevertheless, the implant appears safe, as there were no signs of inflammation in the rats and the implant stayed in place during follow-up.