INNOVATION
Harley Street surgeon develops artificial retina
The bionic eye is no longer just a work of science fiction, thanks to the pioneering achievements of a Harley Street surgeon. The Clinical Services Journal reports on the latest innovation to restore human vision.
Over the last few years, ophthalmologist Professor Lyndon Da Cruz, who carried out the first bionic eye surgery in the UK, has used technology to enhance or restore human vision. The surgery was so effective that people who were almost blind can now read large letters, words and locate objects. “I work with people who have suffered profound vision loss and it was very frustrating for me to have nothing to offer those with a severe retinal disease,” commented Professor Da Cruz. “Suddenly, advances in technology made it plausible to investigate solutions to conditions we had no treatment for.” He explained that the ‘bionic eye’ isn’t actually an eye; with the many complex structures that would entail. It is a device designed to replicate the role of the retina – turning light into electrical signals which are then sent off to the brain. “A better name would be an artificial retina,” Professor Da Cruz continued, “because the device has to be implanted into a normally-shaped and structured eye, with a functioning optic nerve.” The human retina works using cells about one micron wide and 100 microns long, a micron being 1,000th of a millimetre, so a straight replication of retinal structures is still a long way off. Instead, the team have developed a multi-part system. The system is made up of a video camera set within a pair of glasses, and a computer which converts the feed from the camera into a series of electrical signals. These signals are transmitted wirelessly to a receiver on the eye, which passes the signals to electrode array of the artificial retina that stimulates the residual retina. The signals created are sent to the brain. Professor Da Cruz said: “The artificial retina is the heart of the system, the interface between the technological and biological realm. It is made up of 60 electrodes, laid out in a six-by-10 grid. The signals it receives stimulate the electrodes to produce specific patterns in set time sequences. “In a sense, it is drawing a moving picture on this grid. This is sent down the optic nerve to the brain. We have a long way to go in terms of
Patients who had been totally blind could see light. The very best patients could read letters two or three centimetres high on a computer screen.
replicating the density of electrical stimulation that you get in the normal eye, but it is still quite an extraordinary micro-engineering feat.” As the surgeon, Professor Da Cruz’s role was to develop the nature of the retinal implant and then refine the procedures
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needed to put the implant in place, to the point where they can be carried out by any competent ophthalmic surgeon. He was then responsible for monitoring the operation of the device after the procedure, collating the data provided by patients about living and working with it. His work represents the final link in the technological chain. The visual environment is incredibly complex, so the first task was to enable the device to extract useful information from the camera feed. This involves extremely subtle computer algorithms, which sift through the signals to filter out extraneous information and build a useful image out of what is left. This is then transmitted to the eye and to the retinal implant, which must operate without damaging the optic nerves in any way. This technological-to-biological interface has required very sophisticated developments by material scientists.
SEPTEMBER 2017
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