“…Important insights in outer segment structure and formation have been achieved using qualitative microscopic observations and manual quantification of POS (Carter-Dawson and Lavail, 1979;Hollyfield and Rayborn, 1979;Guerin et al, 1993;Mayhew and Astle, 1997;Rakshit et al, 2017). This includes representative images of immunohistochemical staining of photopigments (e.g., rhodopsin and S-or M/L-opsin), proteins involved in the signal transduction cascade (e.g., recoverin, transducin, arrestin, phosphodiesterase), or structural markers of POS (e.g., peripherin, ROM1; Assawachananont et al, 2014;Daum et al, 2017;Shindou et al, 2017;Tu et al, 2019;Gasparini et al, 2022;West et al, 2022;Yamasaki et al, 2022;Völkner et al, 2023). Electron microscopy or tomography images were used to assess POS structure, volume, disc assembly, and size (Carter-Dawson and Lavail, 1979;Obata and Usukura, 1992;Eberle et al, 2012;Gilliam et al, 2012;Burgoyne et al, 2015;Ding et al, 2015;Goldberg et al, 10.3389/fnmol.2024.1398447 Frontiers in Molecular Neuroscience 03 frontiersin.org 2016; Daum et al, 2017;Ribeiro et al, 2021;Gasparini et al, 2022).…”