Forty years ago, an 18-year-old man was diagnosed with retinitis pigmentosa, an inherited disease where patients lose their light-sensitive cells in the retina at the back of the eye as a result of several genetic mutations. The genes that usually code for functional proteins in the retina instead fail to do so, or otherwise produce abnormal ones that instead cause damage to the surrounding retinal tissue. The condition affects about 1 in 4000 people worldwide, and can sometimes cause complete blindness, just as it did with the now-58-year-old patient. Now, with the help of some light-sensing algal proteins, gene therapy, and specially-engineered goggles, they can now perceive fuzzy shapes and locate them.
The study, published in Nature Medicine, involved inserting genes that code for ChrimsonR, a bioengineered version of a light-sensing protein found in unicellular algae, into a modified virus. The modified viral vectors were then injected into one of the patient’s eyes. ChrimsonR falls under a category of light-sensitive proteins called channelrhodopsins, and has been modified to react to flashes of amber light within the reddish end of the color spectrum. By injecting these proteins into the retinal area of the patient’s eye, the researchers hoped to make these retinal cells more sensitive to yellow-orange light.
The specially-engineered goggles come into play by picking up changes in light intensity from its environment and converting them into intense amber images that are projected straight into the patient’s retina, with the researchers hoping this would activate ChrimsonR. After months of treatment, enough ChrimsonR had accumulated inside the patient’s retina—enough for them to perceive the patterns projected by the special goggles, restoring some of his lost vision.
Prior to the treatment, the patient could not perceive any light at all, with or without the special goggles. The goggles only started to help them out once they had undergone enough treatment with ChrimsonR. Eventually, the patient had some of his visual ability restored, with them being able to identify cups and notebooks placed in a table in front of them, despite not always being able to correctly identify how many objects were placed.
Of course, the treatment has not restored the patient’s vision completely, and the study is currently limited in both image resolution and image colors projected onto the patient’s retinas, as the goggles currently only allow monochromatic images from the amber light. The study has also only been done on one patient so far. Despite this, Dr. Botond Roska, senior author of the study and founding director of the Institute of Molecular and Clinical Ophthalmology Basel in the University of Basel, Switzerland, remains hopeful that the study will help pave the way for future research into gene therapy for restoring vision into blind patients, saying that “the findings provide proof-of-concept that using optogenetic therapy to partially restore vision is possible.”
Bibliography
- Sahel, JA., Boulanger-Scemama, E., Pagot, C. et al. Partial recovery of visual function in a blind patient after optogenetic therapy. Nat Med (2021). https://doi.org/10.1038/s41591-021-01351-4
- Lanese, N. (2021, May 25). Genes from algae helped a blind man recover some of his vision. LiveScience. Retrieved August 18, 2021, from https://www.livescience.com/man-partially-recovers-sight-after-gene-therapy.html
