The influence of antiepileptic drugs on eye movements

Abstract

In order to detect the influence of antiepileptic drugs, eye movements were recorded in patients (n = 53) suffering from generalized epilepsy on monotherapy with antiepileptic drugs or not on drug therapy, and in a control group (n = 28). The test procedure included visually guided saccades, smooth pursuit tests and visual suppression of caloric induced nystagmus. The authors found a significant increase in latency of saccades in the group treated with phenytoin and evidence of fluctuation of performance, expressed in incidental slow saccades or increased latency, in the phenytoin and carbamazepine group and in the patient group without treatment. No effect of sodium valproate on saccades could be detected. The carbamazepine group showed a reduced gain of smooth pursuit eye movements, negatively correlated with the serum level. This might be an explanation for the known side-effects of carbamazepine. No effect of the other drugs on smooth pursuit could be demonstrated. In all subjects visual suppression of caloric induced nystagmus was complete. The results in the patient group without treatment point to a potential influence of epilepsy of itself on eye movement parameters. In the authors' opinion, recording of eye movements can be useful in an attempt to objectify subjective complaints. However, because of the considerable intersubject variability in eye movement parameters, it is not recommended as a routine procedure in the management of epileptic patients in place of assessment of serum levels of antiepileptic drugs.

Key Words:

• epilepsy
• eye movements
• antiepileptic drugs
• drug toxicity
• electrooculography