To determine whether short-term strict control of blood glucose can improve abnormal visual evoked potentials (VEPs) in poorly controlled diabetic patients with no overt diabetic complications.
VEPs (P100 wave latencies) were recorded in 12 poorly controlled diabetic patients (7 with insulin-dependent diabetes mellitus and 5 with non-insulin-dependent diabetes mellitus) before and after at least 3 days of near normoglycemia obtained by continuous subcutaneous insulin infusion (CSII). Exclusion criteria were overt diabetic neuropathy or retinopathy. The control subjects were 12 healthy subjects matched for age and sex. Fifty-two other subjects formed a reference control population. The intra-individual coefficient of variation for P100 latency was < 3%.
The P100 latencies were longer in diabetic patients than in control subjects (means of both eyes ± SD: 116.8 ± 10.1 vs. 106.2 ± 4.5 ms, P < 0.01), and 4 of the 12 diabetic patients had abnormal VEPs. After 3 days of close blood glucose control (mean blood glucose profile fell from 13.7 ± 2.2 mmol/l to 6.8 ± 1.2 mmol/l, P < 0.01), the mean P100 latencies were significantly shorter (112.5 ± 7.6 ms, P < 0.01) but were still significantly longer than control values. The longer the initial P100 latency, the greater the decrease after CSII. There was no correlation between the fall in blood glucose and improvement in VEPs.
Short-term blood glucose normalization is associated with improved P100 wave latency in uncomplicated diabetic patients. These data suggest that abnormal VEPs are partly reversible and include functional disturbances related to glucose metabolism.
