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The effects of beta sympathetic drugs on positive accommodation (accommodation for near vision) were studied in vervet monkeys. Isoproterenol, a beta sympathetic stimulator, depressed the positive accommodation function. It was not a complete antagonist since 3 to 4 diopters of accommodation remained. Only atropine, a parasympathetic blocker, could abolish these 3 to 4 D as well as the entire function. In many of the experimental animals, positive accommodation function was biphasic. The initial component had a flatter slope, lower amplitude, and lower threshold of stimulation than the second. The transition point of the components was between 2 and 4 D. Beta sympathetic stimulation appeared to abolish selectively the second component while parasympathetic inhibition abolished both components. It appeared that peripherally, parasympathetic inhibition was a more potent and thus more important mechanism in antagonizing positive accommodation than beta sympathetic stimulation.

The effects of alpha sympathetic drugs on positive accommodation (accommodation for near vision) were studied in 15 vervet monkeys. Levarterenol 5%, a predominantly alpha stimulating drug, when applied topically in one eye produced a depression in accommodation in that eye. This response appeared to be mediated through beta receptor sites, since it was inhibited by propranolol, a beta sympathetic antagonist, rather than phentolamine, an alpha inhibitor. Larger topical doses (10%) or subconjunctival administration of 5 mg or more, when given unilaterally, depressed accommodation bilaterally without dilating the contralateral pupil. These effects appeared to be indirectly induced. It would seem from our studies that stimulation of alpha sympathetic receptors served no important function in antagonizing positive accommodation.