Posted on: Tuesday 25 May 2021
The BBC covered a story on Monday 24 May about optogenetics partially restoring the sight of a man living with retinitis pigmentosa in France.
The latest news is a first-in-human test of an optogenetics approach and has established proof of principle in human vision.
Is it gene specific?
This approach is not dependent on genetic diagnosis but is currently only appropriate when sight loss is very advanced. It can potentially restore some functional vision to improve independent mobility, as demonstrated by the individual who received the treatment; the first things he could see after treatment were the white lines of a zebra crossing. It will not restore ability to watch TV, read etc.
How does it work?
This approach uses gene therapy techniques to provide cells at the back of the eye with the genetic instructions to build a light sensitive protein; in this particular case, the protein is normally found in algae. The genetic instructions are injected into the eye contained within a harmless virus.
The treatment targets cells that are not normally light sensitive in a healthy eye, they simply relay messages from the light sensitive photoreceptors to the optic nerve. However, they remain undamaged in RP, so can be put to use when the photoreceptors have degenerated.
The treated individual needs to wear special goggles / glasses to control the intensity of light entering the eye and adjust the wavelength of the light so that it better suits the algal protein.
Is the treatment effective immediately?
It took several months after treatment before this individual saw the zebra crossing, as his eye and brain had to adapt to a new way of processing visual information.
Are there any other similar treatments being developed?
Various research groups and biotechnology companies are investigating this approach with various different light-sensitive proteins. Some may not require the use of the special goggles, but these have not yet reached human trials.
When I can access this treatment?
All of these treatments will require several years of clinical testing before they can be considered for widespread use.