Simultaneous Prosthetic Central Vision & Natural Peripheral Vision in Atrophic AMD Patients

Article: Implanted chip, natural eyesight coordinate vision in study of macular degeneration patients
Source: Stanford Medicine
Published: February 4, 2022

Macular degeneration leads to loss of photoreceptors in the macula, which is responsible for clear central visual acuity; however, the low-resolution (20/200) peripheral vision remains unaffected. In an interim report, prespecified in the initial protocol, researchers followed the progress of three patients with geographic atrophy (atrophic age-related macular degeneration) from the five recruited in the initial feasibility trial two years ago, to assess whether or not the patients could coordinate seeing simultaneously with both the PRIMA photovoltaic retinal implant and their natural peripheral vision. The proesthetic vision is achieved through a stream of intensified near-infrared video projected onto the macula from specially designed augmented reality glasses. The invisible light activates the photovoltaic pixels, which replace the eye's natural photoreceptors, to initiate visual signals to downstream retinal ganglion cells that relay the signals to the brain.

PRIMA retinal implant inside area of geographic atrophy.
Magenta oval represents area of near-infrared light projected
onto the retina from the augmented reality glasses.

A few months after surgery, the patients were able to sense light and simple patterns using the prosthetic. The investigators report that the wireless 2 x 2 mm-wide 30 µm-thick chip, having 378 pixels of 100 µm in size, allowed the patients to have central vision with equivalent Snellen visual acuity of 20/460 to 20/565 (Landolt acuity of 1.17 ± 0.13 pixels), improved to 20/63–20/98 with electronic magnification of up to a factor of 8. In the present follow-up, the research team tested visual perception by projecting a line directly onto the retinal implant with the near-infrared camera while another line of a different color was displayed at a distance in room lighting, the latter eliciting peripheral vision in the affected eye as well as vision from the fellow eye. Senior author of the project states that patient had "no trouble properly seeing both patterns at once...indicating that the brain can perceive the prosthetic and natural retinal codes simultaneously." Compared to previous retinal implants that conferred distorted vision, the perception of a coordinated, coherent image "is very exciting news," he adds. They next plan to make improvements in image resolution with smaller pixels, as well as to test the prosthesis in more natural settings and for longer durations.

My rating of this study: ⭐⭐

Palanker D, Le Mer Y, Mohand-Said S, et al. "Simultaneous perception of prosthetic and natural vision in AMD patients." Nature Communications.  13:513. 26 January 2022. https://doi.org/10.1038/s41467-022-28125-x