Natural history of diabetic microangiopathies.

Diabetic microangiopathy is better called diabetic microcirculatory disease, because it is characterized by as well dysfunction of small vessels and as increased capillary basal membrane thickness. Its role for the development of tissue damage is not fully understood and might vary in different organs. Therefore, the two diabetic complications which are assumed to be typical manifestations of the diabetic micro-circulatory disease like retinopathy and nephropathy have to be described separately. We have studied the natural history of diabetic retinopathy and nephropathy only in insulin-dependent diabetics. This was done because micro-vessel disease is more common in this type of diabetes than in patients with non-insulindependent diabetes mellitus. Also the onset of diabetes is usually more wellknown in IDDM than in NIDDM. Only young insulin-dependent diabetics were studied in order to avoid confusion from age-related complications. First some epidemiological facts about retinopathy which indicate the seve rity of the problem. The prevalence of legal blindness in a diabetic population living in a limited geographic area of Denmark was shown by Vesti Nielsen1) to be 7.9 percent in insulin-dependent diabetics and 4.6 percent in orally treated noninsulin-dependent diabetics. Seventy-five percent of the blind insulin-dependent diabetics were blind from retinopathy, whereas only 40 percent of blind noninsulin-dependent diabetics were blind from retinopathy. The cumulative inci dence of blindness in a population of 264 juvenile insulin-dependent diabetics followed for more than 40 years was 16 percent2). In a further 15 percent vision became so much reduced that the patients were unable to read the newspaper without magnifying glass2). Thus, diabetic retinopathy is the most common cause of acquired blindness among professionally active persons in Denmark. This is also the case in the United States. It is hoped that the prognosis for vision will improve significantly after the introduction of photocoagulation treatment and vitrectomy in the treatment of diabetic retinopathy. A precise description of the natural history of diabetic retinopathy has been difficult until now, because of the lack of quantitative measurements of patholo