MERTK and diabetic retinopathy: The precise role of Ccl4 in retinal degeneration has yet to be examined, although protein levels are increased in the aqueous humour of AMD patients [76], and its expression is up-regulated concomitantly with emergence of retinal degeneration in experimental light damage [41], diabetic retinopathy, and Abca4−/−Rdh8−/− and Mertk−/− mice [34].