Effects of 670 nm light treatment on the population of photoreceptors hyperoxic mice. (A) Representative micrographs of retinal sections showing the nuclear layers stained with Bisbenzimide (blue). To account for obliquely cut retina and possible artefacts, the ratio of the ONL (white line) to the OLM-ILM (red line) was used for analyses. (B) Quantitative analysis of photoreceptor nuclei density in the inferior central region of NT group (black bar) and Tr mice (red bar). Compared with the nontreated retinas at 14d hyperoxia (14dNT), treatment with 670 nm red light induced a significant level of photoreceptor nuclei density preservation in the 14dTr group (*p < 0.001). Scale bar 50 μm in A.