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We'll even come to you

The Bionic Eye - The way forward?

A British man has become the first person in the world to receive a bionic eye implant that corrects for age-related macular degeneration (AMD)—the most common cause of vision loss in adults. The implant was a success: previously, the patient had no central vision at all; now, he has low-resolution central vision. The operation was carried out at Manchester Royal Eye Hospital; the recipient of the implant was Ray Flynn, aged 80.

The macula is at the back of the eye, in the central region of the retina. It is responsible for all of your high-resolution central vision—that is, when you gaze directly at something, it is the visual receptors in the macula that turn the light that reaches them into vision. With AMD, detritus (called drusen) slowly builds up between the vascular layer of the eye (the choroid) and the retinal pigment epithelium (RPE)—the layer that rods and cones are attached to. If too much drusen builds up, blood flow to the RPE is reduced enough that the rods and cones wither.

AMD happens quite slowly, but eventually it can result in a complete loss of central vision, which makes it hard to recognise faces, read books, interact with computers, and so on. AMD is common amongst older people, and as our average life expectancy continues to increase, so does the number of people with AMD: about 500,000 people have it in the UK, and between 2 and 3 million people have it in the US.

Which brings us neatly onto the Argus II, a retinal prosthesis made by Second Sight. The Argus II consists of two parts: an internal implant, and external equipment that the patient must wear. The implant has an electrode array that is embedded in the eye's retina, a battery, and a wireless antenna. Externally, there is a pair of glasses that has a forward-facing camera and a radio transmitter, and belt-worn video processing unit.

The camera captures the scene in front of the implantee, and then sends that signal to the VPU for processing. That processed signal is then sent back up to the glasses, where a transmitter beams the signal over to the implant's antenna. Finally, the video is "output" to the electrode array, which in turn stimulates the optic nerve. The electrode array has a resolution of about 60 "pixels," which is enough for the implantee to track the movement of objects, to see simple patterns and shapes, or to slowly read large letters. The vision provided by the Argus II implant is monochrome, too, though some research groups are working on encoding the electrode stimuli so that the brain can perceive colour.

The prosthesis itself isn't actually new: it has previously been used to treat retinitis pigmentosa, another cause of vision loss, but this is the first time it has been used in a patient with AMD. Both the US and EU have approved the Argus II for treating retinitis pigmentosa; now it looks like Second Sight is performing a clinical trial to get it approved in the EU for treating AMD. Technologically, it sounds like both the internal and external equipment are the same.

So far, though, Paulo Stanga—the lead surgeon for Flynn's implant—says that "it's going better than expected ... Mr Flynn's progress is truly remarkable, he is seeing the outline of people and objects very effectively. I think this could be the beginning of a new era for patients with sight loss."

This post originated on Ars Technica UK



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