Factors influencing the natural history of diabetic retinopathy

Despite recent improvements in the management of blood glucose control and in modern technology such as laser treatment and vitreoretinal surgery, diabetes mellitus is the major systemic cause of blindness in the Western world. The study of the natural history of diabetic retinopathy is difficult because of the variability of the disease, and the numerous factors that may influence its course and outcome. In the many studies available of the natural history of diabetic retinopathy, there is a failure to identify these factors. This article tries to identify and to classify the influences that may modify the outcome and the natural course of diabetic retinopathy, and gives some advice on how to deal with them. They can be subdivided into external, internal and ocular factors. Any future studies of the natural history of diabetic retinopathy are marred by the fact that effective treatment is now established and the guidelines for when to commence treatment and the techniques of treatment are well documented.