Robotic prothesis and sight: retinal implants

Maximum precision with minimal volume. It is the aim to pursue when prothesis are planted in delicate and small dimensions organs as the eye, to reproduce its functions.

Up to twenty years ago the concept that electronical devices could bring back sight seemed science fiction. It seemed an abstract matter, but recenlty retinal implants have been developed. In cases like this, it is necessary that brain and environment communicate, letting the brain perceive the visual stimulus and decode them.

It is sure that being made of a so complex anatomy, its repoduction is difficul. Nowadays, Europe has approved the devices Argus II and Alpha Ims, for those who have an irreversible degeneration of retina, but that keeps the activity of optical nerve. Rather than expensive (100 thousand  euros) the two prothesis funtion in different ways.

Argus II is made by microchips with 60 electrodes , that is planted in the rear part of retina and communciates with optical nerve   and by an antenna placed on ocular bulb, that receives impulses from a camera mounted on glasses.

Alpha Ims, instead,doesn't need an external camera: a microchip composed by 1.500 light-sensitive photodiodes it is inserted in the area of reatina that generally hosts visual receptors and sends impulses to optical nerve. Moving with the eye, it allows to direct the gaze in a natural way, on the opposite way of the camera of Argus II that has to be directioned moving all the head.

An independent study published on the British Journal of Ophtalmology  compared the two implants, concluding that Alpha Ims allows a major visual acuity. The implant of this prothesis it is more complex. In both the cases, anyway, the resulting vision is coarse. The patient sees some pixels in gray scale and, with time, he learns how to decode them. For blind people this is a big thing. But there are already being experimented retinal implants that should allow a more precise vision, while also softwares for already existing prothesis should allow to see colors in short time. 

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