Continuous insulin infusion therapy and retinopathy in patients with type I diabetes

The effect of continuous subcutaneous insulin infusion (CSII) and conventional injection therapy (CIT) on retinopathy was evaluated in a 1-year crossover study (6 + 6 months) with 54 type I diabetic patients. The glycaemic control improved significantly but did not reach euglycaemic levels during CSII (P less than 0.01-0.001), whereas no change was observed during CIT. At baseline, 50% of the patients had no retinopathy, 20% had only minimal changes, 26% had moderate background retinopathy, and 2 patients had proliferative changes. During CSII, the retinopathy grade impaired in 7 patients, whereas no deterioration occurred during CIT. Improvement of retinopathy grading was observed in 2 patients during CSII and in 5 during CIT, respectively. Individual retinal lesions also progressed more and improved less during CSII (12:3) as compared with CIT (10:9). The net impairment in both retinopathy grading and individual lesions was significant during CSII as compared with CIT (P less than 0.05). There was no difference in the baseline characteristics (severity of retinopathy, age, sex, duration of diabetes, insulin dose, blood pressure, serum creatinine), in the fall of glycosylated haemoglobin or number of hypoglycaemic episodes between the patients with and without worsening of retinopathy during CSII. The present study suggests that even a moderate improvement in metabolic control induced by CSII may be associated with a risk of progression of retinopathy during the first months of therapy.