Presented by The Center for Neuroengineering and Therapeutics Presents and The Bioengineering Department.

Check email for zoom link or Everett Prince at eprince@seas.upenn.edu.

Retinal degenerative diseases lead to blindness due to loss of the “image capturing” photoreceptors, while neurons in the “image-processing” inner retinal layers are relatively well preserved. Information can be reintroduced into the visual system using electrical stimulation of the surviving inner retinal neurons. We developed a photovoltaic substitute of photoreceptors which convert light into pulsed electric current, stimulating the secondary retinal neurons. Visual information captured by a
camera is projected onto the retina from augmented-reality glasses using pulsed near-infrared (~880nm) light. This design avoids the use of bulky electronics and wiring, thereby greatly reducing the surgical complexity. Optical activation of the photovoltaic pixels allows scaling the number of electrodes to thousands. In preclinical studies, we found that prosthetic vision with subretinal implants
preserves many features of natural vision, including flicker fusion at high frequencies (>30 Hz), adaptation to static images, antagonistic center-surround organization and non-linear
summation of subunits in receptive fields, providing high spatial resolution. Results of the clinical
trial with our implants (PRIMA, Pixium Vision) having 100μm pixels, as well as preclinical
measurements with 75 and 55μm pixels, confirm that spatial resolution of prosthetic vision can
reach the pixel pitch. Remarkably, central prosthetic vision in AMD patients can be perceived
simultaneously with peripheral natural vision. For broader acceptance of this technology by patients who lost central vision due to agerelated macular degeneration, visual acuity should exceed 20/100, which requires pixels smaller than 25μm. I will describe the fundamental limitations in electro-neural interfaces and 3-dimensional configurations which should enable such a high spatial resolution. Ease of
implantation of these wireless arrays, combined with high resolution opens the door to highly functional restoration of sight.