Retinal Implants: The Artificial Silicon Microchip

Based on the knowledge that nerves behind the retina still functioned even when the retina had degenerated, as shown by Dr. Mark Humayun (Publication can be found here), researchers have been focusing on creating artificial retinas as a means of restoring vision. One such device that is capturing a lot of attention is Optobionic's Artificial Silicon Retina™ microchip.


"Ophthalmologists Implant Five Patients with Artificial Microchip". 

ScienceDaily, Apr 29, 2005.

The first retinal implant to move into clinical trials (currently Phase II), the ASR chip contains approximately 5,000 microscopic solar cells, called microphotodiodes, that convert light into electrical impulses. The chip is inserted into the subretinal space and basically takes on the role of photoreceptors: in response to light entering the eye, it sends the information along to the brain for interpretation. What is special about this microchip is that it requires no external battery source; the chip powered solely by incident light. This distinguishes the ASR from one of its competitors, ARCC (Artificial Retina Component Chip). The ARCC, like the ASR, is composed of light sensors and electrode arrays that send signals to the retinal neurons. However, the system requires additional power and is dependent upon an external camera to detect a picture and induce a laser pulse. Both the camera and the laser are built into a pair of sunglasses, which the patient will wear. Incoming laser light is then detected by the photo sensors in the implant to create a picture. The ASR is thus a much more elegant solution in terms of convenience and aestheticism.


The fact that the ASR does not require any external power also greatly reduces the size of the chip (2 mm in diameter, 25 microns in thickness and is less than the thickness of a human hair) and makes surgery less invasive. In addition, the microchip is strategically placed so as to directly stimulate the remaining healthy cells in the retina. Of the 10 patients who received the microchip implant surgery, all reported some degree of improvement in visual function.

Photo credit: Optobionics

The ASR™ is only one of the numerous artificial retinas that are currently undergoing FDA

approval. Although complete vision rescue has not be reported, being able to see hints of 

light has been a big step for most patients. Below are two patients describing what they were able to do after the implant surgeries: