retinal implant

Implanted digital devices have to be the ultimate in “wearables;” they effectively become part of your body. Some digital implants are almost commonplace, such as the cochlear implants that can help the deaf hear again. One field in this area that has seen rapid advances is that of sub-retinal implants that can help the blind see again. Early attempts were very low resolution and most designs require the use of an external camera to provide an image. German researchers have come up with a device that addresses both of these shortcomings.

Retina Implant AG has developed a device that is implanted in the back of the eye, behind the retina. A tiny 3 mm by 3 mm chip holds a matrix of 1,500 sensors. Each one has a photodiode that is sensitive to light, and an associated electrode that stimulates the patient’s optic nerve directly. The device requires very little power, which is supplied wirelessly. An induction coil is implanted just under the skin behind the ear, and an external power pack is connected to it. Magnets cause the two wires to stick together to provide steady power. Last fall at the American Academy of Ophthalmology (AAO) annual meeting, the company reported on the results of its first 29 subjects. 72 percent of the patients showed improvement in performing daily tasks, recognizing shapes, and their mobility. 86 percent were able to detect light. No patients experienced any adverse events from the implants.

The device is only designed for those patients with retinitis pigmentosa (RP), though it may be suitable for others causes for loss of vision. At this point, subjects must have had at least 12 years of vision before losing it, and have not been blind for more than 20 years. It is not suitable for patients who have lost their vision due to stroke, macular degeneration, glaucoma, or diabetes. In spite of these limitations, we can expect further improvement in the technology, resulting in higher resolution images, possibly even to the point where the implants could make it possible for the patients to read again.