Progress towards a high-resolution retinal prosthesis

Abstract

Electronic retinal prostheses represent a potentially effective approach for restoring some degree of sight in blind patients with retinal degeneration. Functional restoration of sight would require hundreds to thousands of electrodes effectively stimulating remaining neurons in the retina. We present a design of an optoelectronic retinal prosthetic system having 3mm diameter retinal implant with pixel sizes down to 25 micrometers, which allows for natural eye scanning for observing a large field of view, as well as spatial and temporal processing of the visual scene to optimize the patient experience. Information from a head mounted video camera is processed in a portable computer and delivered to the implanted photodiode array by projection from the LCD goggles using pulsed IR (810 nm) light. Each photodiode converts pulsed light (0.5 ms in duration) into electric current with efficiency of 0.3 A/W using common biphasic power line. Power is provided by the inductively-coupled RF link from the coil on the goggles into a miniature power supply implanted between the sclera and the conjuctiva, and connected to subretinal implant with a thin 2-wire trans-scleral cable.3-dimensional structures in the subretinal prosthesis induce retinal migration and thus ensure close proximity between stimulating electrodes and the target retinal neurons. Subretinal implantations of the 3-dimentional pillar and chamber arrays in RCS rats with 2 and 6 week follow-up demonstrate achievement of intimate proximity between the stimulation cites and the inner nuclear layer. In some instances formation of a fibrotic seal has been observed.

A polymer optoelectronic interface restores light sensitivity in blind rat retinas

“…Interestingly, our organic photovoltaic device proved to possess a remarkable light-sensitivity, with a response threshold of 0.3 μW/mm 2 , 30-fold lower than the ocular safety limit for continuous exposure to visible light (106.93 μW/mm 2 ), and a response saturation at 100 μW/mm 2 , still below the limit. Moreover, the response threshold closely matched the range (0.1-10 μW/mm 2 ) of retinal irradiance during common daily outdoor activity 41,42 , thus suggesting a possible future implementation without any external light projectors. Another interesting feature of our interface is related to the linear dynamic range of operation covering 2 log units of retinal irradiation (1-100 μW/mm 2 ).…”