Rapid Deterioration of Diabetic Retinopathy During Treatment with Continuous Subcutaneous Insulin Infusion

The effect of continuous subcutaneous insulin infusion (CSII) on diabetic retinopathy was studied in 19 patients with insulin-dependent diabetes mellitus (IDDM). All had diabetes before age 30. Three patients had no retinal abnormalities at the start of the study, 12 had minimal or mild background retinopathy, and 4 had a preproliferative retinopathy. The follow-up period was 12–14 mo. Fundus photography and fluorescein angiography was performed every 2–6 mo. Despite marked improvement of metabolic control, none of the patients with retinopathy showed reversal of the fundal abnormalities. In seven patients with background retinopathy the abnormalities remained unchanged; in five patients a slight worsening was noted. Four patients with moderate-to-severe background retinopathy showed a rapid and severe progression of the fundal abnormalities into a florid proliferative diabetic retinopathy 3–6 mo after initiation of CSII. A higher incidence of hypoglycemic episodes could not be demonstrated in this group. Two of these patients showed a marked reduction in glomerular filtration rate (GFR), 34% and 38%, respectively, during the course of their follow-up. This is compared with a decrease in GFR by only 5.6% for the group as a whole. The four patients with rapidly progressive retinopathy all had long-standing poorly controlled diabetes with preproliferative retinal changes, diabetic neuropathy, and, with the exception of one patient, signs of nephropathy at the start of CSII. The incidence of these features was nil or very low in the remaining 15 patients. This study and similar ones raise the question of whether rapid improvement in glycemic control, after long periods of poor control, could result in rapid deterioration of retinopathy, especially in those with diabetes of long duration or with preproliferative changes.