Toward a wide-field retinal prosthesis

Abstract

The purpose of this article is to present a wide field electrode array that may increase the field of vision in patients implanted with a retinal prosthesis. Mobility is often impaired in patients with low vision, particularly in those with peripheral visual loss. Studies on low vision patients as well as simulation studies on normally sighted individuals have indicated a strong correlation between the visual field and mobility. In addition, it has been shown that increased visual field is associated with a significant improvement in visual acuity and object discrimination. Current electrode arrays implanted in animals or human vary in size; however, the retinal area covered by the electrodes has a maximum projected visual field of about 10°. We have designed wide field electrode arrays that could potentially provide a visual field of 34°, which may significantly improve the mobility. Tests performed on a mechanical eye model showed that it was possible to fix flexible polyimide dummy electrode arrays of 10 mm wide onto the retina using a single retinal tack. They also showed that the arrays could conform to the inner curvature of the eye. Surgeries on an enucleated porcine eye model demonstrated feasibility of implantation of 10 mm wide arrays through a 5 mm eye wall incision.

Variation in Performance of Platinum Electrodes with Size and Surface Roughness

“…The size range has been chosen on the basis of the device requirement for larger electrodes of greater than 200 µm diameter to safely stimulate potentially distal neurons (25) in comparison with cortical prostheses where microelectrodes usually penetrate into and are in contact with the target tissue. However, the visual field imparted by a vision prosthesis is directly related to the size of the stimulated area of the retina, and hence, the overall dimensions of the electrode array, (26) which are determined from both the electrode diameter and packing limitations of the fabrication process. A study by Onnela et al has suggested that either novel electrode materials or surface treatment methods will be required to meet the charge injection needs of a high resolution of vision prosthesis.…”

Retinal Prosthesis

“…Ameri et al describes a foldable array that can be inserted through a small sclerotomy (eye wall incision), then expanded once in the eye. [52] This approach allows 1 cm wide array, thus 45-50 degrees of visual angle. Subsequent development of this idea has demonstrated long-term implantation of these arrays into animal eyes.…”

Translational Prospects for Human Induced Pluripotent Stem Cells

“…Other advantages for this disease as an initial target of iPS cell therapies are that surgical procedures for grafting are well studied [75], considerable effort has gone into developing prostheses, which helps inform technical approaches to the eye and assays for following patients [76], and there is recent industry interest in iPS-derived RPE cells [77]. In addition, long-term follow-up of animals that received human ESC-derived RPE revealed no major safety issues [78].…”