Towards a completely implantable , light - sensitive intraocular retinal prosthesis

An electronic retinal prosthesis is under development to treat retinitis pigmentosa and age-related macular degeneration, two presently incurable diseases of the outer retina that afflict millions worldwide. Previous studies have established the feasibility of the retinal prosthesis. Short-term tests in blind humans have shown that degenerated retina will respond to light in a way that is consistent with f orm vision [1]. Post-mortem analysis of human eyes with RP and AMD show a significant survival of inner retinal cells despite near complete degeneration of the photoreceptors in the outer retina [2]. Long-term implants have demonstrated that the retina can tolerate the physical presence of an electrode array without degenerating due to pressure or other mechanical affects [3]. The focus now has turned towards the development of a chronic stimulator [4]. Initial prototypes based on current technology will have a small number of pixels and will place the stimulation electronics outside the eye. However, more advanced devices are in the early development stages. A completely implantable, light-sensitive retinal prosthesis must include capability for both phototransduction and stimulus current generation, two power intensive functions. These devices will be implanted in the eye, creating a significant source of heat that must be dissipated by the ocular tissue without