The relationship between tonic vergence and oculomotor stress induced by ethanol.

Previous investigations have demonstrated an ethanol-induced increase in distance esophoria and an increase in near exophoria, together with a decrease in negative fusional ability, the AC/A ratio and near point of convergence. The present study (N = 10) was designed to test the hypothesis that these effects are due to a biasing of vergence towards its tonic resting state when under conditions of oculomotor stress. Measurements of the parameters before and 1 hr after imbibition of a moderate dose of ethanol supported the previous findings. Darkroom measures of tonic vergence (vernier alignment) and tonic accommodation (laser optometry) were unaffected by ethanol. The study indicates that the changes in oculomotor function induced by the central inhibitory action of ethanol represent a shift towards the tonic vergence position.