Oculomotor consequences of beta-adrenoceptor antagonism during sustained near vision.

The effect of a topical non-selective beta-adrenergic antagonist, timolol maleate (0.5%) on the response accommodative convergence/accommodation (AC/A) ratio was monitored during a 16 min near-vision task. A double-blind protocol was adopted between timolol and a saline control for 17 emmetropic subjects. Timolol produced a significant reduction in AC/A during the first 4 min of the task with respect to saline. This reduction was mediated via accommodative convergence and it is proposed that this demonstrates direct involvement of sympathetic innervation to the ciliary muscle during the initial stages of a near-vision task.