There is clear evidence that diabetes affects retinal circadian clock rhythms and alters circadian gene expression in the retina in both type 1 and type 2 diabetic models (Busik et al., 2009; Di et al., 2019; Lahouaoui et al., 2014, 2016; Qi et al., 2020; Wang et al., 2014). The gene discussed is CLOCK; the disease is diabetes mellitus.