Reduced progression of diabetic retinopathy after islet cell transplantation compared with intensive medical therapy

Background. Diabetic retinopathy is a major complication of type 1 diabetes and remains a leading cause of visual loss. There have been no comparisons of the effectiveness of intensive medical therapy and islet cell transplantation on preventing progression of diabetic retinopathy. Methods. The British Columbia islet transplant program is conducting a prospective, crossover study comparing medical therapy and islet cell transplantation on the progression of diabetic retinopathy. Progression was defined as the need for laser treatment or a one step worsening along the international disease severity scale. An interim data analysis was performed after a mean 36-month follow-up postislet transplantation and these results are presented. Results. The medical and postislet transplant groups were similar at baseline. Subjects after islet transplantation had better glucose control than the medically treated subjects (mean HbA1c 6.7%+/- 0.9% vs. 7.5 +/- 1.2, P<0.01) and were C-peptide positive. Progression occurred significantly more often in all subjects in the medical group (10/82 eyes, 12.2%) than after islet transplantation (0/51 eyes, 0%) (P<0.01). Considering only subjects who have received transplants, progression occurred in 6/51 eyes while on medical treatment and 0/51 posttransplant (P<0.02). Conclusions. Progression of diabetic retinopathy was more likely to occur during medical therapy than after islet cell transplantation.