Artificial retinas to provide a little vision

eyeimplant.jpgPeople are doing some amazing things to get a little sight back for folk who have lost theirs.

Some sight fails even though the nerves behind the retina are undamaged – in conditions like retinitis pigmentosa and age-related macular degeneration, for example.

At the ISSCC semiconductor conference in San Francisco this week, two Californian teams described chips that sit on the retina surface and stimulate the nerves behind to produce the sensation of vision.

Both use external cameras, and wirelessly transfer power and data to circuits in and around the eye – one with 512 pixels and the other with 1,024.

The University of Tuebingen in Germany has been doing something similar for a while without using an external camera (pictured above).  

Instead, it has 1,500 photo-sensitive pixels on its top surface of a chip and an equivalent array of stimulation electrodes on the bottom.

This one is installed under the defective (but transparent) tissue layer – there is an article on it in the proceedings of the Royal Society.

Power comes through a transcutaneous cable entering the person’s neck. Later versions will use an internal battery.

A slightly lower-tech solution is to put a stimulation array on another part of a someone’s body. Dr Paul Bach-y-Rita seems to have been a pioneer of what he called sensory substitution.

The person’s back has been used via an array of solenoids, and quite a bit of success has been had with electrical tongue stimulation via an electrode array – with as many as 12×12 electrodes – pretty coarse resolution, but useable.

No operation is needed and tongue stimulator box and its array can be carried in the pocket when they are not being used.

Having read around a bit, it seems that some users eventually ‘see’ the image rather than having to think about interpreting it.

BrainPort is one such device, sold in the US with a whole bunch of caveats.

‘Alice’

The two ISSCC papers are:
16.5 – A 37.6mm2 1024-channel high-compliance-voltage SoC for epiretinal prostheses
(University of California, Los Angeles)
16.6 – A fully intraocular 0.0169mm2/pixel 512-channel self-calibrating epiretinal prosthesis in 65nm CMOS
(CalTech, Doheny Eye Institute, and University of Southern California, Los Angeles)

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