DLN: Photovoltaic Restoration of Sight in Age-related Macular Degeneration, Prof. Daniel Palanker (Stanford)
Retinal degenerative diseases lead to blindness due to loss of the 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 and allows scaling the number of electrodes to thousands.
Preclinical studies demonstrated that prosthetic sight with subretinal implants preserves many features of natural vision, including flicker fusion, adaptation to static images, antagonistic center-surround and non-linear summation of subunits in receptive fields, providing high spatial resolution. Clinical trial in AMD patients confirmed that letter acuity closely matches the 100 micrometers pixel size of the first generation of the PRIMA implant (Pixium Vision). Remarkably, central prosthetic vision is perceived simultaneously with the peripheral natural vision.
To reduce the pixel size while providing sufficiently deep stimulation, we are developing various field shaping strategies. Grating acuity with 75, 55 and 40 micrometer pixels in rats matched the pixel pitch, while with 20micrometers, it reached their natural acuity limit of about 28 micrometers. Ease of implantation of these wireless arrays, combined with high resolution, opens the door to highly functional restoration of sight.
Daniel Palanker is a Professor of Ophthalmology and Director of the Hansen Experimental Physics Laboratory at Stanford University. He received MSc in Physics in 1984 from the Yerevan State University in Armenia, and PhD in Applied Physics in 1994 from the Hebrew University of Jerusalem, Israel.
Dr. Palanker is working on optical and electronic technologies for diagnostic, therapeutic, surgical and prosthetic applications, primarily in ophthalmology. In the field of biomedical optics, these studies include interferometric imaging of neural signals, and laser-tissue interactions with applications to retinal laser therapy and to ocular surgery. In the field of electro-neural interfaces, Dr. Palanker is developing retinal prosthesis for restoration of sight to the blind and implants for electronic control of organs.
Several of his developments are in clinical practice world-wide: Pulsed Electron Avalanche Knife (PEAK PlasmaBlade, Medtronic Inc.), Patterned Scanning Laser Photocoagulator (PASCAL, Topcon Inc.), Femtosecond Laser System for Cataract Surgery (Catalys, Johnson&Johnson), Neural stimulator for enhanced tear secretion (TrueTear, Allergan Inc.). Photovoltaic Retinal Prosthesis (PRIMA, Pixium Vision) is in clinical trials.