Also known as an artificial or bionic retina, retinal implant devices can be used in people with advanced retinal degenerations such as Retinitis pigmentosa (RP) and Age-related macular degeneration (AMD). In these conditions, the photoreceptor cells of the retina do not work as they are supposed to.
However, often the nerve cells that relay the signal to the brain (the ganglion cells) are still intact after many years. The possibility of restoring a form of vision using retinal implant technology and provide patients with a greater sense of autonomy is promising.
Retina implant technology involves the use of microelectronics and microchip electrodes surgically implanted into the back of the eye (retina) to directly stimulate these functional retinal nerve cells, bypassing the damaged photoreceptor cells. There are currently at least four microchip devices that are being developed and have been implanted in human eyes.
These include IRIS®II bionic vision system and PRIMA system (developed by Pixium Vision); Argus II (a retinal prosthesis system developed by Second Sight Medical Products) and the Alpha IMS (a subretinal implant developed by Retina Implant AG in Germany). All devices, with the exception of PRIMA, have received CE Mark. This is a European regulatory marking that means the product meets safety and reliability standards and means they can be sold in Europe.
Currently these devices are only offered to people with advanced retinal degenerations such as Retinitis pigmentosa (RP), Age-related macular degeneration (AMD)and Choroideremia but may include other pathologies that cause sight loss in the future.
These individuals had sight through childhood but are now completely visually impaired or have minimal light perception. Because the brain must interpret the devices signals, a person who has been visually impaired from birth would never have had the opportunity to develop this capacity and therefore unlikely to benefit from the technology.
To date, visual function outcomes following implantation of these devices have been limited to perception of shapes and objects and basic navigation. Key to success of this process is the rehabilitation of patients.
Individuals have to re-learn how to see and their brains need to learn how to interpret the new kind of information being received from the device. Retinal implant technology continues to evolve with scientists, ophthalmologists, mathematicians and physicists all working together to further optimise and improve on the capabilities of current and future retinal devices.
Some of the challenges facing these experts include the development of a smaller implant device, compatibility with the curvature of the eye, a greater number of electrodes, more sophisticated data processing capabilities and increased resolution for facial recognition.
Central to this process is the interaction with patients who provide invaluable insight and feedback to developers into the performance of the device and how it may be adapted to improve day to day living. In this way, patients will actually become part of the validation and innovative stages, driving the development and optimisation of retinal implant devices and enabling them once again to perform tasks of ordinary day-to-day life.
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