Thanks to the implant, he gained the ability to recognize everyday objects including spoons, bananas, and apples; he could read a clock; and he could read letters, albeit slowly, and they had to be printed extremely large (about 5-8 cm high).
Videos of his abilities and his reactions to his newfound sight are available online.
This subretinal implant is not the only “bionic eye” idea under development, however. Other researchers have been working on using an external camera which transmits information to a relay chip placed on the retina, the "epiretinal” approach.
However, Zrenner’s team argues that their subretinal implant technique has some important advantages. Epiretinal devices have to pre-process the image before sending it to the retina, and patients need time to learn how to process the information that their brain receives, because the camera isn’t able to provide an exact simulation of normal retina outputs.
Zrenner et al’s subretinal method, however, took little “getting used to” because the implant is such a close analogue of the healthy retina. Also, they say that epiretinal approaches have so far only provided up to 60 pixels, as opposed to their 1,500.
Still, the technology has limitations. The image has no color, and it’s much less detailed than normal vision. The sensor has a resolution of 38 by 40 pixels, compared to the 960 by 640 resolution of an iPhone screen.
Being so small, it only covers a small fraction of the normal retinal field. However, this is actually less of a problem than it might first appear, because all of our detailed vision takes place in a tiny part of the retina, called the fovea. By placing the implant where the fovea used to be, the quality of the images was maximized.
The chip also requires an external power supply, so patients need to carry the battery pack and control unit around with them. Finally, they have a fairly hefty wire coming out of the side of their head.
So, at the moment, science is very far from being able to fully restore vision, but it’s still an exciting step forward. Technical improvements are sure to bring higher-quality images in the future.
Other researchers are working on using gene therapy to cure the underlying molecular cause of the disease, preventing the photoreceptors from dying in the first place. This approach has shown promise in animal models, and the results of the first human trials of gene therapy in another genetic eye disease, Leber’s ameurosis, have recently appeared.
So whether this device will become widely used in the treatment of people with diseases like retinitis pigmentosa is unclear. But it joins other emerging technologies, from deep brain stimulation to brain-computer interfaces, which are blurring the boundaries between the nervous system and machines.
Are you a scientist? Have you recently read a peer-reviewed paper that you want to write about? Then contact Mind Matters co-editor Gareth Cook, a Pulitzer prize-winning journalist at the Boston Globe, where he edits the Sunday Ideas section. He can be reached at garethideas AT gmail.com