Development of an implantable epiretinal vision prosthesis with integrated image acquisition (OPTOEPIRET)

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In Germany about 10,000 people are suffering from Retinitis Pigmentosa. No treatment for this disease slowly leading to blindness is established. Seven percent of all blindness is caused by this disease. The photoreceptors (cones and rods) which convert the incoming light into electrical pulses are dying off gradually. Despite of the destroyed photoreceptors the connections from retinal nerve cells to the brain are partly still functioning. Therefore by electrically stimulating retinal nerve cells action potentials can be generated that are transmitted via nerve fibers to the visual cortex and processed to optical perceptions. Researchers are worldwide working on retinal prostheses based on electrical stimulation. These approaches differ in the placement of the stimulation electrodes. In the most sophisticated approaches the stimulation electrodes are placed epiretinally or subretinally. Implants that are used in humans today have in common that due to the small size of the electrode array only a small area of the retina can be stimulated. So the field of vision is very small and corresponds to only about 9°. The recovery of the peripheral recognition cannot be achieved with these systems. However the peripheral function of the retina is indispensable for autonomous movement in rooms. This capacity is dropped out first in retinitis pigmentosa patients. Whereas in the epiretinal approach an increase of the diameter of the stimulation array is still possible and by this an increase of the visual field, the subretinal approach will be very limited due to the danger of separation of the retina or further surgery complications. Within the proposal OPTOEPIRET the epiretinal approach will be extended by an integrated epiretinal recording of the image produced by the eye lens onto the retina. For this a flexible stimulation array with a diameter of about 12 mm (which corresponds to a visual field of about 40°) based on a thin flexible polyimide substrate will be developed. The backside of this substrate is faced to the eye lens. Thinned and therefore flexible camera-chips will be integrated having the same number of photodiodes as there are stimulation electrodes. The photodiode-array will now record the image produced by the eye-lens that would normally fall onto the retina. Integrated CMOS-circuitry converts this optical information in appropriate stimulation pulses that are forwarded to the electrodes on the front side of the substrate. By this approach no external image processing will be necessary.