OPN4 and Hyperglycemia: Although an earlier study showed that 15 weeks of hyperglycemia in STZ-diabetic rats did not change the number of melanopsin-positive RGCs, and a reduction in light-induced cFos expression in the suprachiasmatic nuclei could be reversed by surgical removal of the lens, suggesting that diabetic cataract formation may be partly responsible for changes in the melanopsin-mediated pathway [22].