Project Summary The Food and Drug Administration's approval of Luxturna marked a new era in the fight to cure blindness caused by inherited retinal degenerations (IRDs). However, despite an approved treatment for RPE65- mediated disease, there are still over 280 molecularly distinct, currently untreatable IRDs that cause vision loss from progressive death of the rod, cone, and retinal pigment epithelial (RPE) cells. Further, treatment with Luxturna does not fully restore vision to normal levels in RPE65-mediated disease, particularly for foveal cone vision, and there is variability between patients in the amount of vision gained post-treatment. Numerous therapeutic approaches, including gene therapies similar to Luxturna, are under development for IRDs. To maximize chances of success, it is critical to understand the natural sequence of degeneration in each disease, both to optimize the timing and retinal location of applied therapies as well as to enable precise evaluation of whether the therapies had an effect. We will use multi-modal adaptive optics scanning light ophthalmoscopy (AOSLO) to simultaneously observe the cone inner segment (IS) and waveguiding outer segment (OS) mosaics and RPE mosaics to identify AO structural phenotypes in IRDs. We will also use AO microperimetry and optoretinography to test photoreceptor function in the same IRD patients. Finally, we will measure the AO structural and functional responses to Luxturna gene therapy for RPE65-mediated disease and AAV2.hCHM gene therapy for choroideremia. Based on our preliminary and published data, we hypothesize that cone function correlates with structural phenotype, cones exhibit dysfunction prior to their structural loss, gene therapy will slow or halt structural degeneration, and gene therapy will reverse photoreceptor dysfunction at retinal locations where cells are structurally intact but functionally compromised. The information gained through our studies will enable cellular scale assessment of the safety and efficacy of gene therapy and the will validate AO cellular scale outcome measures for use in future clinical trials.