Retinal degeneration is among the leading causes of incurable blindness. Through a variety of mechanisms, such diseases lead to progressive loss of photoreceptors, while the inner retinal neurons remain relatively well preserved. Multiple approaches to restoration of sight are being explored, including visual prosthetics, optogenetics, cell transplantation and gene therapy.
We developed a photovoltaic array replacing the lost photoreceptors to electrically stimulate the inner retinal neurons. This implant is wirelessly powered by near infrared light projected from video goggles, thereby enabling minimally invasive modular implantation to tile a large visual field. In rats blinded by retinal degeneration, such implants with 70mm pixels restored visual responses with spatial resolution corresponding to half of the normal visual acuity. In the human eye, such resolution corresponds to an acuity of 20/250, and we are preparing this system for a clinical trial, and developing implants with smaller pixels.
Second approach is based on co-transplantation of the photoreceptor sheets along with retinal pigment epithelium (RPE). Recently we discovered robust migration and rewiring of adult photoreceptors to deafferented bipolar cells after local photoreceptor injury, which indicates a possibility of rewiring of the transplanted photoreceptors to the host degenerate retina. To replace the RPE lost in retinal degeneration, we will transplant it together with the photoreceptor sheet. The target cellular layers are extracted from the donor tissue using interferometric image-guided laser ablation. If successful, this approach has the potential of restoring natural vision in blind patients.