The relative importance of the parasympathetic and sympathetic nervous systems for accommodation in monkeys.

The refractive state of monkeys was followed during preganglionic oculomotor nerve stimulation and during preganglionic sympathetic nerve stimulation performed against a background of oculomotor stimulation. It was found that oculomotor stimulation rates of 2 to 5 per second gave accommodative responses of about 1 to 3 D, and 20 to 50 stimuli per second gave about 6 to 11 D of accommodation. Accommodation followed changes in oculomotor stimulation within 1 to 2 seconds. The effect of sympathetic stimulation performed against a parasympathetic background was small and developed and vanished much more slowly. If it is permissible to draw conclusions from nerve stimulation experiments, it seems that sympathetic nerve activity is of very small importance for desaccommodation. There is a proportion of individuals who would gain from a sympathetic distance accommodation, but because of the slowness of the effect its importance remains questionable.