Eyes, enucleated from euthanized mice, were flash-frozen in liquid nitrogen, embedded in Tissue-Tek optimal cutting temperature compound (Electron Microscopy Sciences, Hatfield, PA, USA), and cryosections were prepared for immunohistochemistry as previously described.12 (link) Sections were incubated with fluorescein isothiocyanate–conjugated peanut agglutinin (FITC-PNA, catalog number L7381; Sigma-Aldrich Corp.) or cone arrestin (catalog number AB15282; Millipore, Temecula, CA, USA) to detect cone PRCs. Additional cryosections were incubated with rabbit anti-glial fibrillary acidic protein (GFAP) (catalog number Z0334; Dako Corp., Carpintaria, CA, USA) to detect gliosis. Alexa Fluor 555 and Alexa Fluor 488 anti-rabbit IgG (Invitrogen, Thermo Fisher Scientific, Waltham, MA, USA) were used as the secondary antibody for cone arrestin and GFAP, respectively. Coverslips were mounted using Fluoroshield with 4′,6-diamidino-2-phenylindole (DAPI) (Sigma-Aldrich Corp.). Retinas were examined using a Zeiss (Carl Zeiss, Göttingen, Germany) Axio Imager D2 microscope equipped with a high-resolution camera and processed using Zeiss Zen23pro software.