BenevolentAI
August 1, 20232010 – 2013
August 1, 2023Retinal Implants
Retinal implants are one of the most promising therapies for retinal degenerative diseases. They replicate the function of damaged photoreceptors and create nervous impulses that translate into visual cortex stimulation and partial vision restitution...
Retinal degenerative diseases are considered a significant cause of blindness worldwide. The most common ones are Retinitis Pigmentosa and Age-related Macular degeneration. (1) Although their pathophysiological processes differ, they can cause progressive, non-reversible vision loss. Since Humayun (1990) discovered that low current stimulation of dissected retinal tissue could produce retinal responses, many projects have been developed to restore sight to patients with these inevitable diseases. Among many, retinal prostheses have delivered the most promising results. (2,3)
Retinal Implants
Retinal implants are artificial intelligence artifacts designed to replicate the function of damaged photoreceptors by converting visual information into electrical neural signals.(2) Reaching the high processing capacity of the human visual system has proved to be an unrealistic goal. However, the simulated prosthetic vision studies and the bidirectional enhancement system have allowed implants to estimate the optimal spatial-temporal image processing technique to magnify areas of interest while removing redundant information in the visual field. This way, visual information can travel from an external video camera to the retinal ganglion cells, the optic nerve, and the occipital cortex. (3) After many years of research and development, in 2013, the FDA approved the Argus II system as the first long-term therapy for patients with advanced retinitis pigmentosa. (4)
Retinal implants are artificial intelligence artifacts designed to replicate the function of damaged photoreceptors by converting visual information into electrical neural signals.(2) Reaching the high processing capacity of the human visual system has proved to be an unrealistic goal. However, the simulated prosthetic vision studies and the bidirectional enhancement system have allowed implants to estimate the optimal spatial-temporal image processing technique to magnify areas of interest while removing redundant information in the visual field.
This way, visual information can travel from an external video camera to the retinal ganglion cells, the optic nerve, and the occipital cortex. (3) After many years of research and development, in 2013, the FDA approved the Argus II system as the first long-term therapy for patients with advanced retinitis pigmentosa. (4)
How it works:
Argus II consists of internal and external components; the first is a video camera mounted in a pair of glasses that captures the information from visual scenes. Next, a coil near the camera sends the data to an optical processing unit in the patient’s belt. This unit converts visual information into a set of radio waves and generates a specific stimulation pattern. Next, these patterns are sent wirelessly to a subconjunctival receiving coil, translating radio signals into electrical impulses. Finally, a ribbon of cables connects the coil with an epiretinal-located electrode array which directly stimulates the ganglion cells and starts the nerve stimulation. (3,5) Figure taken from Weiland and Humayun. (6)
Argus II consists of internal and external components; the first is a video camera mounted in a pair of glasses that captures the information from visual scenes. Next, a coil near the camera sends the data to an optical processing unit in the patient’s belt. This unit converts visual information into a set of radio waves and generates a specific stimulation pattern. Next, these patterns are sent wirelessly to a subconjunctival receiving coil, translating radio signals into electrical impulses.
Finally, a ribbon of cables connects the coil with an epiretinal-located electrode array which directly stimulates the ganglion cells and starts the nerve stimulation. (3,5) Figure taken from Weiland and Humayun. (6)
What is next?
Retinal implants have become invaluable for patients older than 25 with profound outer retinal degeneration. They induce subjective visual precepts (phosphenes) by applying an electrical current across the ocular surface. However, the high neuro-cortical integration of our optical system has been challenging to replicate. Although it is considered an excellent start, the 60 microelectrodes of the Argus II can only accomplish a theoretical maximum visual acuity of 20/1600, being 20/1262 the best-reported result. Thus, new systems are working on creating smaller electrodes allowing a higher concentration of units that would translate into better visual outcomes. Patients can now process localization, orientation, and mobility, allowing them to interact with their surroundings. (3,7)