Optoelectronic vision

Generally speaking, there are three types of blindness. The first is optical blindness where light is prevented from passing through the cornea. The cornea, aqueous humor, lens and vftreous humor must be transparent, or nearly so, if the person is to see well. Anything that clouds any of these media Witerferes with visn. Corneal transplantation, keratoprosthesis lirplantation, cataract surgery with intraocular lens implantation and vitreoretinal procedures can resolve most cases of this type of blindness. The second Is retina Blindness due to photo receptor damage or retina detachment, such as Retinitis Pigmentosa ( RP ). Every year, blindness disease due to retinal degeneration relegates thousands of people to painfully dark lives. The third optical nerve blindness resulting from injury or disease of the Optical nerve. Scientists have searched every discipline to find eftective methods of treating blindness, such as using aids based on conversion of the optical image, to auditory or tactile StimUk. However, the Umited performance of such equipment and difficulties in training patients have seriously harrçered praaI applicahons. A great edification has been given by the discovery of Foerster (1929)1 and Krause & Schum (1931)2, who found that the electrical stimulation of the visual cxrtex evokes the perception of a snI spot light called phosphene' in both blind and sighted subjects. According to this principle, It is possible to Invite artificial vision by using stimulation with electrodes placed on the vision neural system, thereby developing a prosthesis for the blind that migt4 be of value in reading and mobility. In fact, a number of investigators have already exploited this phenomena to produce a funtional visual prosthesis, bringing about great advances in this area.