Washington: Scientists have developed a retinal implant that transmits visual information to the brain to help visually impaired people recognise common objects.
Argus II, is the first FDA-approved retinal implant that helps people who have lost their vision due to a blinding genetic disease. Retinitis pigmentosa is a group of genetic disorders that affect the retina's ability to respond to light.
The disease causes slow loss of vision, beginning with decreased night vision and loss of peripheral vision and eventually leads to blindness. There is currently no cure for retinitis pigmentosa.
The Argus II retinal prosthesis is a system in which a miniature video camera is housed in the subject's glasses and sends information to a patient-worn video processing unit where the image captured by the camera is processed into instructions which are then transmitted wirelessly to a retinal implant fitted with 60 electrodes.
These electrodes pulse to stimulate cells in the retina, transmitting visual information along the optic nerve to the brain, creating the perception of patterns of light.
In the study, eight patients wearing the retinal prosthesis were asked to identify white or metallic objects against a dark background, then were asked to identify the same objects with enhanced outlines.
The tests were done in three ways - with the retinal prosthesis turned on in a standard mode, in a scrambled mode as a positive control, and turned off as a negative control.
The results for solid object identification rose from 12.5 per cent correct with the device switched off to 32.8 per cent with the device on with 26.2 per cent correct identification when the device was scrambled.
Results for the outlined object identification were at 9.4 per cent with the device turned off and 41.4 per cent with the device on, with 20.7 per cent correct identification in scrambled mode.
"Despite the small sample size, statistically the results have achieved significance due to the magnitude of change in the performance of the use of the device within each subject," said Yvonne Luo, from London's Moorfields Eye Hospital NHS Foundation Trust and lead researcher on the study.
"Moreover, these subjects represent people with the most severe form of the disease," Luo said.
The Argus II is the only device currently on the market in the US and is one of several devices intended to help people suffering from this disease.
Other devices and therapies in development include an implanted microchip, electrical stimulation therapy, implantable capsules of timed-release medication, nutrient therapies to reduce retinal damage and gene therapies to halt or reverse retinitis pigmentosa.
The research was presented at the Annual Meeting of the American Academy of Ophthalmology in New Orleans.
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