Background: Diabetic retinopathy is one of the most common causes of blindness among adults.

Aim: To report the natural history of diabetic retinopathy among Chilean patients with type 1 diabetes followed for a mean of 18 years.

Material and methods: Retrospective review of medical records of 39 patients aged 26 to 70 years, (20 females, 78 eyes) with type 1 diabetes controlled by the same ophthalmologist from 1971 to 2008. A questionnaire was sent to each patient and their treating physician to request information about the evolution of the disease and metabolic control.

Results: The questionnaire was answered by 24 patients (62%) and 21 attending physicians (54%). Small hard drusen were observed in 25 patients (64%). In 12 cases the drusen were detected before the development of any type of retinopathy. Eleven women became pregnant and retinopathy progressed in four of them. Twenty three patients (59%) developed proliferative diabetic retinopathy (PDR). Patients with PDR had a significantly longer duration of diabetes and worse glycemic control. There was a higher frequency of diabetic nephropathy in the PDR group, but only 13 patients out of 23 with PDR had nephropathy. The retinopathy progressed to high risk PDR two years after successful kidney-pancreas transplantation in one patient.

Conclusions: In patients with type 1 diabetes mellitus, small hard drusen may be the initial manifestation of diabetic retinopathy. Risk factors for progression to PDR were duration of diabetic and poor glycemic control. Nephropathy was more prevalent in patients with PDR, but a significant group of PDR patients did not have demonstrable nephropathy.