This study used survival analysis on 2199 patients who had reached vision-threatening diabetic retinopathy to investigate the contribution of heredity to diabetes together with other known risk factors for the development of either proliferative diabetic retinopathy (PDR) or diabetic macular oedema (DMO). Unlike previous studies, this review showed that female relatives with type 1 diabetes were a protective factor for the development of PDR two to 11 years of diabetes duration. This implies that the role of heredity for developing any retinopathy and PDR may differ. Conversely, heredity to diabetes increased the risk for developing DMO until 24 years of diabetes duration, and this confirms that this risk is maintained for many years after onset of diabetes. Furthermore, it is postulated that heredity between the patient and the relative with diabetes plays a larger role for the risk of developing DMO than shared lifestyle. The authors conclude that heredity might be added as an independent risk factor in the decision models for recommendation of screening intervals for diabetic retinopathy, and that PDR and DMO should be separate end points in screening programs.