Abstract 121
Aims: To assess whether electrophysiological abnormalities in visual functions exist in newly - diagnosed diabetic patients. Subjects: 20 control subjects (10 male) with mean ± SD age 19.7 ± 4.7 years and 14 patients (7 male) with insulin dependent diabetes mellitus (IDDM), age 19.1 ± 3.9 years, with HbA1c 9.8 ± 1.9 %. Measurements: Visual evoked potentials (VEP) were recorded basally and after photostress (PS) when blood glucose levels ranged between 90 and 125 mg/dl. These measurements were repeated after 6 months when all patients reached a good metabolic control (HbA1c 7.2 ± 1.5%). Results: P100 latency was higher in diabetics than in controls (100.2 ± 6.2 ms vs 92.1 ± 3.9; p<0.01) while N75-P100 amplitude was similar in both groups (9.1 ± 0.9 µV vs 9.0 ± 0.9; ns). The recovery time of VEP after PS was equivalent in patients and controls. After PS a significant (p<0.01) increase in P100 latency was found in diabetics (after 20 s:105.7 ± 3.1 ms; after 40 s 100.1 ± 3.0; after 60 s: 99.1 ± 2.9) and in controls (after 20 s:116.9 ± 2.9 ms; after 40 s: 113.2 ± 2.6; after 60 s: 110.1 ± 3.6). The mean increments in P100 latency found at 20, 40 and 60 sec after PS were similar and the difference between controls and diabetics continued to be significant (p<0.01). The mean percentage decrements of N75-P100 amplitude at 20, 40 and 60 sec after PS were significantly lower in controls than in diabetics (15.09 ± 1.9% vs 26.9 ± 3.1; p<0.01). At the 2nd evaluation, we found a complete normalisation of the all parameters that became similar to those of controls (P100 latency: 92.2 ± 3.8 vs 92.7 ± 3.6).
