Previous research has focused on the expression of key nucleotide-inactivating/ADO-producing enzymes: ecto-nucleoside triphosphate diphosphohydrolase-1 (NTPDase1, also known as CD39), NTPDase2 and ecto-5′-nucleotidase/CD73 in primate [15–17], rodent [3, 8, 17–19], and zebrafish [19, 20] retinas in terms of their role in control of angiogenesis, diabetic retinopathy, intraocular pressure, and neurovascular coupling. Here, ENTPD1 is linked to diabetic retinopathy.