Extraocular approach to retinal prosthesis evaluated in animal study

An extraocular approach may offer a new route for research into retinal prostheses for blind patients, an animal study suggests. Retinal stimulation with a prototype extraocular retinal prosthesis was tested for feasibility by researchers in Australia.

Vivek Chowdhury, MB, BS, and colleagues, performed a study in cats to determine the feasibility of developing a low-resolution retinal prosthesis using electrodes placed on the outer surface of the eye. Dr. Chowdhury and colleagues evaluated electrode configurations and parameters for stimulation of the eye. A 21-electrode extraocular retinal prosthesis array was sutured to the sclera of anesthetized cats over the lateral surface of the eye.

The researchers recorded electrically evoked potentials (EEP) in response to stimulation with the electrode array.

Electrical stimulation of the lateral retina with the electrode array elicited EEPs that were higher in the ipsilateral visual cortex, according to the study.

“EEP amplitude increased with increases in stimulus pulse duration and current intensity,” the study authors said. “The thresholds for retinal excitation are below safe charge-density limits for chronic neural stimulation. Ipsilateral localization of the EEP suggests that localized retinal stimulation is occurring.”

The study is published in the August issue of the ANZ Journal of Surgery.