ELECTROPHYSIOLOGICAL ASSESSMENT OF VISUAL FUNCTION IN NEWLY-DIAGNOSEDIDDM PATIENTS

Electrophysiological tests (electroretinogram, oscillatory potentials, visual evoked potentials, in the basal condition and after photostres s) reveal an abnormal function of the visual system in insulin-depende nt diabetic (IDDM) patients. The aim of our work was to assess whether electrophysiological abnormalities in visual function exist in newly- diagnosed diabetic patients free of any fluorangiographic signs of ret inopathy. Ten control subjects (age 28.7 +/- 2.44 years) and ten IDDM: patients (age 25.2 +/- 6.78 years; disease duration 5.3 +/- 3.5 month s) in stable metabolic control (HbA(1C)7.5 +/- 1.1%) were evaluated. F lash-electroretinograms and oscillatory potentials were similar in bot h groups. Visual evoked potentials (VEP) recorded under basal conditio ns showed that P100 latency was significantly increased in the diabeti c patients compared to control subjects (p < 0.01), while N75-P100 amp litude was similar in both groups. The recovery time of VEP after phot ostress was equivalent in diabetic patients and control subjects. The impaired basal VEPs suggest an early involvement of the nervous conduc tion in the optic nerve. However, the preserved flash-electroretinogra m and the normal recovery time after photostress indicate that a short disease duration does not induce physiopathological changes in the ou ter retinal layers or in the macular function.