Involvement of the visual evoked potentials in type 2 diabetes

Objective :To assess the function of the optic pathway in type 2 diabetics without retinopathy (40 subjects) or with mild Non Proliferative Diabetic Retinopathy (40 subjects). Methods: VEPs , elicited by means of pattern-reversal stimulation, were studied in a group of 80 non-insulin-dependent diabetics . Results: In subjects suffering from diabetes for less than 10 years, with mild retinopathy or without retinopathy, the amplitude N75-P100 decreased, and this is statistically significant with stimulation at 15’. As the time from disease onset increases, VEP latency (P100) shows a greater increase with the use of small checks (15’), than with large checks (30’) and this becomes statistically significant after 20 years (p =0.01) . There is a positive correlation between VEP-latency and the duration of the diabetes. No correlation was found with other parameters taken into consideration, such as patient age, plasma-glucose level at 8 a.m., mean daily plasma glucose and glycosylated-haemoglobin. Conclusion: The amplitude N75-P100 decreased in subjects suffering from diabetes type 2 for less 10 years. VEP latency increases (in type 2 diabetics) 10 years after disease onset. Functional deficiency of the central retinal layers seems to precede retinopathy. This finding might prove to be a useful index for the evaluation of visual neuropathy.