Effect on refraction of intramuscular pilocarpine in two species of monkey (Cercopithecus aethiops and Macaca irus)

The effect on accommodation of pilocarpine given intramuscularly was studied on two species of monkey (Cercopithecus aethiops and Macaca irus), six young individuals of each species. The results are given as dose-response curves; 0.2 mg. per kilogram of pilocarpine caused little change in refraction, generally less than 2 D., and 2.0 mg. per kilogravi caused a large change in refraction in both species, always more than 12 D. The accommodation of the Cercopithecus seemed a little more sensitive to pilocarpine than that of the macaque. One out of four monkeys receiving very large doses behaved unexpectedly. Increasingly large doses of pilocarpine caused decreasing myopia, whereupon atropine increased the myopia. This mechanism is not understood.