The glycemic levels of anesthetized ZDF rats were, however, unaffected as were those of insulin treated ZDFs which remained at 5–12 mmol/L.ERG measurements were made under dark-adapted (scotopic) and light-adapted (photopic) conditions periodically between 8 (approximately 2 weeks after the onset of hyperglycemia in ZDF rats) and 22 weeks of age, after which untreated diabetic animals start to develop visible cataracts. Here, INS is linked to cataract.