The artificial retina we have heard about in the newspapers in recent days is called Alpha AMS. It is produced by a German company, Retinal Implant AG. It is a microchip, similar to that of a digital camera, implanted under the retina. To date, around 20 have been implanted around the world. The use of this type of artificial retina is limited to patients suffering from retinitis pigmentosa who have completely lost their sight, that is, who no longer even perceive light or who have a weak perception of it.
How the Alpha AMS Artificial Retina works
The Alpha AMS artificial retina works like this: the microchip is implanted under the retina and would replace the function of the photoreceptors (cones and rods) damaged. Under normal conditions we are able to see because objects reflect light which, upon entering the eye, activates the photoreceptors. These produce an electrical signal which reaches the brain via the optic nerve. When the photoreceptors are damaged by a disease such as retinitis pigmentosa, the implantation of this microchip can partially replace their function. When the microchip is hit by light it produces an electrical signal that replaces the one produced by the damaged photoreceptors. The microchip implanted under the retina needs an external energy source to function. For this reason, a receiver is implanted behind the ear under the skin, which is connected to the microchip with a ceramic cable and is then recharged using an external unit. The maximum vision that can be achieved with this artificial retina model is 0.07 which is equivalent to approximately 7% of what a normal eye sees with a field of vision reduced to approximately 13 degrees. He also lacks color perception. The patient would see in black and white according to what Retinal Implant AG, manufacturer of the device, claims.
When to use the Alpha AMS Artificial Retina
Today the only indication for the use of this artificial retina model is Retinitis Pigmentosa in cases where other ocular diseases are not present and the patient has managed to develop significant vision at a young age. Patients who can consider this type of intervention are only those who do not even perceive light or have a weak perception of light. If your vision is better, it is not worth considering this type of surgery.
When not to use the Alpha AMS Artificial Retina
The Alpha AMS Artificial Retina cannot be used in cases of reduced vision resulting from these diseases:
Other Artificial Retina models: Argus II Retinal Implant
There is another model of artificial retina called Argus II retinal Implant developed by the American company Second Sight which is based on the same principle, however it requires more complex external armamentarium. In this case the experience is broader with 39 cases implanted in Italy. The patient wears glasses on which there is a camera that receives the light signal of objects and subsequently wirelessly transfers an electrical signal to a set of electrodes placed at the retinal level. More information at http://www.secondsight.com/system-overview-en.html
Current critical issues of the Artificial Retina
The artificial retina currently represents great hope for patients suffering from retinitis pigmentosa who have completely lost their sight, however there are currently important critical issues that have not yet been resolved by the advancement of technology. These devices placed inside the eye need an energy source and this requires a connection between the inside of the eye and the outside for the microchip to work. This is unfortunately associated with a high risk of infection within the eye with a consequent risk of losing the eye itself rather high over time. Studies are currently underway to exploit the energy produced by eye movements and thus eliminate the external energy source. The image resolution provided by the artificial retina models currently available , the Retinal Implant Alpha AMS and Argus II Retinal Implant, is rather reduced and therefore the use is currently limited to very selected cases. This is associated with the very high cost of these devices which further limits their use. We are at the beginning of a promising path, just as when the first computer was inaugurated. We hope that the rapid advancement of the technique can lead to more performing and safer devices. Furthermore, in the treatment of retinitis pigmentosa, there are hopes linked to the use of stem cells and the use of gene therapy (Luxturna – Spark Therapeutics) to stop the progression of the disease.