Macular recovery recorded by nyctometry in insulin-dependent diabetes mellitus.

Abstract

Macular recovery, recorded by nyctometry, has been studied in children and adults with IDDM. Impaired macular recovery was found only in a few eyes with normal visual acuity without visible signs of retinopathy, in more than one third of the eyes with slight background retinopathy, in the majority of eyes with advanced background retinopathy, and in all eyes with proliferative retinopathy, suggesting that severe neurosensory disturbance accompanies visible vasculopathy in the retina. A significant correlation between impairment of macular recovery and reduction of the oscillatory potentials of the electroretinogram was found in groups with slight background retinopathy, severe background retinopathy, and proliferative retinopathy, suggesting that changes in these two neurosensory variables concurrently reflect abnormalities in the inner part of the retina corresponding to second order interneuronal connections. Near-normal blood glucose control obtained by continuous subcutaneous insulin infusion (CSII) significantly enhanced both normal and impaired macular recovery. This effect was more pronounced in patients with short duration of IDDM; no effect was found by short-term treatment of a selected group of patients with long-standing metabolic dysregulation and long disease duration. Young patients with normal or slightly impaired macular recovery might possibly benefit from sustained near-normal blood glucose control. Large-scale and long-term studies are needed to confirm this assumption. In a 3-year investigation with CSII, progression into proliferative retinopathy could not be prevented in those patients initially displaying severely impaired macular recovery. However, visible retinopathy did not progress in eyes, in which improvement of within normal or slightly reduced recovery performances had been recorded 6 months in advance. It is suggested that a state of irreversibility, 'point of no return', of retinal pathology, indicated by a certain severe impairment of neurosensory function, might exist. Prospective investigations, 5 years with adults, and 6 years with children, revealed progressive decline in recovery performances during the years of observation, even in eyes with no or slight deterioration of the retinal appearance; and in some eyes retaining no or slight retinopathy, severe impairment of performance developed. Both investigations showed significant differences of initial macular performance between the groups developing proliferative retinopathy and the groups remaining non-proliferative in the periods of observation, suggesting that abnormally reduced recovery performance precede by months or a few years the development of proliferative retinopathy. The development into proliferative retinopathy is generally preceded by increasing stages of background retinopathy running parallel to increasingly reduced macular recovery. The present study has demonstrated large variances of performances both in normal and diabetic individuals.(ABSTRACT TRUNCATED AT 400 WORDS)