Development of Artificial Retinas for the Treatment of Degenerative Eye Disease and the Augmentation of Human Vision

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In the United Kingdom, almost two million people live with some form of sight loss with the most common causes of vision loss being retinal pigmentosis and age related macular degeneration (AMD). AMD affects over 600,000 people in the UK and is expected to rise to almost 700,000 in 2020. Recent studies in the USA have shown that the likelihood of developing AMD increases from 2.5% of population at age 50 to 14% at 80 years old, as the average age of the population continues to increase then this will be a larger problem for future generations.The loss of vision, in general, can be associated the absence or loss of photoreceptors, cones and rods, of the retina while the neural cells in the retinal network remain functional. To date artificial prostheses aimed at restoring vision are currently based on photoactive inorganic semiconductor device structures that have been implanted on the surface or embedded within the retina to stimulate a neuronal response.These devices require complex circuitry, external power and typically suffer from poor biocompatibility and mechanical incompatibility with biological tissue. Improved devices that use the direct photovoltaic response of an implanted array of photodiodes driven by a focussed NIR input that projects the output of an external video camera that samples the visual field.The NIR input is required as currently in these devices the input ambient light is too dim by a factor of at least 1,000 to produce sufficient photocurrent in the implanted devices to directly stimulate neurons. These devices hence give a single input to the patient and are converted to a black and white image by the retinal network.