Four-year follow-up of retinal status and glycosylated haemoglobin in patients with insulin-dependent diabetes mellitus.

Retinal status and glycosylated hemoglobin (GHb) was followed in 32 patients with insulin-dependent diabetes mellitus (18 females; age upon entering the study 26 +/- 8 years; duration of diabetes 10 +/- 6 years; means +/- SD) during a total of 136 patient-years, i.e. during 4.3 +/- 0.6 years per patient. Annual mean GHb (given in percent of the mean normal GHb) was calculated from 7 +/- 3 determinations of GHb per patient-year. Fluorescein angiographs were performed at least once per patient-year, and retinal status was assessed by counting microaneurysms. Upon entering the study, early diabetic (background) retinopathy was present in 14 patients; at the end of the follow-up period, it was present in 20 patients. Retinal status deteriorated in 4/42 patient-years with excellent metabolic control (annual mean GHb less than or equal to 125%), in 13/70 patient-years with good control (annual mean GHb 126-150%) and in 8/24 patient-years with poor control (annual mean GHb greater than 150%). The incidence rate of retinal deterioration differed significantly between years with excellent control and years with poor control (X2 5.7, df = 1, p less than 0.05). It is concluded that excellent metabolic control within 14 +/- 6 years after onset of insulin-dependent diabetes mellitus appears to be a protective factor against the development or progression of early diabetic retinopathy.