I can see said the blind mouse! (and hopefully person in the future)

Retinitis Pigmentosa is a genetic disorder that causes degeneration of the photoreceptor cells in the retina. Due to this degeneration the symptoms often start out with night blindness because the rods are affected first and then eventually become completely blind when the rods and cones both deteriorate (Busskamp et al., 2012). There is currently no cure for retinitis pigmentosa, but optogenetics shows potential as a cure.

Optogenetics is the practice of artificially introducing light sensitive proteins into specific target cells to make them sensitive to light. There are two main light sensitive proteins that are currently used in research: channelrhodopsin-2 found in a type of algae and halorhodopsin found in a haloalkaliphilic archaeon. Channelrhodopsin-2 is a gated channel that depolarizes in response to light, thus activating a cell. Halorhodopsin is a chloride pump that inhibits the cell upon light activation. These two proteins can be isolated and then expressed in target tissues. (Busskamp et al., 2012)

Previous trials for using optogenetics for Retinitis Pigmentosa have used mice that lack functional rods and cones and humans post-mortem. Trials with mice have shown restoration of retinal function by introducing a viral vector containing channelrhodopsin-2 through intravitreal injection. After channelrhodsin-2 was expressed, retinal ganglion cells showed ON responses and the brains of the mice showed visual responses. Furthermore, researchers have found that expressing halorhodopsin in the human retina post mortem resulted in hyper-polarization of the cones when stimulated with light indicating that these proteins could be used in humans. (Busskamp et al., 2012)

While optogenetics shows a promising future for treating some forms of blindness, there is not currently enough human research to advocate for its use in humans yet. However, just this year the first clinical trials for the use of optogenetics for retinitis pigmentosa were approved. In the study, subjects will receive an optogenetic treatment that gives light sensitivity to the ganglion cells and will then be given eyewear that amplifies the light signal to activate these cells (Shaberman, 2018). The future is looking BRIGHT! (pun intended)

Busskamp, V., Picaud, S., Sahel, J.A., and Roska, B. (2012). Optogenetic therapy for retinitis pigmentosa. Gene Therapy 19, 169–175.

Shaberman, Ben. (2018) Clinical Trial to Launch for System Combining Optogenetics and Eyewear - Eye on the Cure.