Retina Implant AG out of Reutlingen, Germany is reporting the publication of a clinical study evaluating the company’s subretinal electronic chips in totally blind volunteers. The device contains 1500 active microphotodiodes, each with "its own amplifier and local stimulation electrode." These then control the generation of electrical impulses going up to the brain representing a 38 × 40 pixel grid. Three people in this study, blind due to hereditary retinal degeneration, were implanted with the device that’s 3mm in diameter. All three reported varying levels of vision and one of the subjects was even able to discern common objects like knives and forks laying on the table.
Core of the implant is a microchip of approximately 3 mm in diameter and 50 μm thickness, with an array of roughly 1500 pixel fields.
Each pixel measures 70 x 70 μm. Photocells, an amplifying circuit, and a stimulation electrode are attached to each pixel field. The photocells absorb the light entering the eye, transforming it into electrical signals. A tiny power line is providing energy from an external source behind the ear. Sixteen additional electrodes are placed for testing purposes at the tip of the implant.
The strength of the light signals controls the amount of current released by each electrode, stimulating the neighboring intact retinal nerve cells electrically. The nerve impulses generated by the retinal cells are processed in the remaining neuronal network of the retina and transmitted via the optic nerve to the visual cortex, creating visual sensations. This is why an unimpaired, regularly functioning optic nerve is an unconditional requirement for the implants’ operational reliability in any approach of a retinal implant.
Press release: Studies Published in Proceedings of the Royal Society B Validates Retina Implant AG’s Clinical Trial Results (.pdf)…
Full study article: Subretinal electronic chips allow blind patients to read letters and combine them to words
Retina Implant Project at Universitätsklinikum Tübingen…
Retina Implant technology page…
Flashbacks: Retinal Implant First Results from Human Trial
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