GRM6 and retinal degeneration: In summary, (1) OBC-targeted Opto-mGluR6 gene therapy remains functional for extended periods of time and is also sufficient in functional vision restoration in later stages of retinal degeneration; (2) for the first time, Opto-mGluR6 gene therapy demonstrated mERGs in optogenetically treated rd1 retina; (3) the presence of Opto-mGluR6 gene therapy decreases retinal hyperactivity typical for the rd1 mouse model of RP; (4) the mGluR6 signalling pathway retains functionality and responsiveness to both pharmacological and optogenetic activation.