CLOCK and diabetes mellitus: While it is established that diabetes distorts clock gene expression in the retina (Busik et al., 2009; Lahouaoui, Coutanson, Cooper, Bennis, & Dkhissi-Benyahya, 2016; Wang et al., 2014), the current study shows that under light/dark conditions only subtle changes in the amplitude and the phase of expression of clock genes were detected.