Researchers based at the Sorbonne Université, Institut National de la Santé et de la Recherche Médicale, CNRS, Paris, have reported partial recovery of visual function in a previously blind patient using an optogenetic strategy combined with a medical device. The research paper, published in Nature, found that the patient was able to perceive, locate, count and touch different objects using a combination of optogenetic treatment wearing light-stimulating goggles. Prior to the treatment, the patient could not visually detect any objects and this provides the “first reported case of partial functional recovery in a neurodegenerative disease after optogenetic therapy”.
The growing field of optogenetics aims to use light sensitive molecules from a variety of biological sources to boost or assist residual activity in a medically relevant context. In the current study, “GS030”, researchers used an optogenetic therapy using adeno-associated viral (AAV) vectors to introduce the genetic sequence of a photosensitive protein into the nucleus of target cells. Once expressed, target cells should be able to function in a similar manner to photoreceptor cells enabling the restoration of vision in patients who are either blind due to RP, or have too few remaining photoreceptor cells to benefit from other potential therapeutic options. As the light sensitivity delivered to such cells is below the capacity of normal photoreceptors, the GS030 treatment additionally employs “biomimetic goggles” (GS030-Medical Device) which, according to their sponsor (GenSight Biologics), “amplify the light signal at the appropriate wavelength to enable vision restoration”. The viral vector encoded the light-sensing channel rhodopsin protein ChrimsonR, fused to the red fluorescent protein tdTomato, which was then administered by a single intravitreal injection.
The 58-year-old patient reported on the study had been diagnosed with RP almost 40 years previously and had only limited visual acuity to light perception. The treatment entailed injecting 5.0 x 1010 vector genomes of optogenetic vector into the worse-seeing eye and using light-stimulating goggles to partially restore visual function. In addition, EEG recordings of occipital cortex signals were modulated by the presence or absence of a visual object and the researchers commented that, “our findings are consistent with the involvement of occipital alpha rhythm fluctuations in object-based visual attention and processing, top-down control of visual attention (for example, to mediate forthcoming visual stimulation processing), stimulus discrimination in object detection and object recognition”. Finally, following reporting at Medscape Ophthalmology, Mr. James Bainbridge, MBChB, PhD, at University College London, stated that, “this exciting new technology might help people whose eyesight is very severely impaired. It is a high-quality study. It is carefully conducted and controlled. The findings are based on laboratory tests in just one individual. Further work will be needed to find out if the technology can be expected to provide useful vision”.