Comparison of subjective lens preference to objective refractive error measurements in pigtail macaques.

Two measurements can be taken to determine the refractive error in human beings: a subjective, lens preference measurement and objective retinoscopy. This study determined the subjective refractive error in eight pigtailed monkeys by placing lenses of different powers in front of peepholes in a solid wall cage and recording the amount of time each subject used the holes. Retinoscopy measurements were then taken and compared to the subjective findings to determine the degree of similarity between these two refraction methods. The results showed a high correlation between the subjective measurements and the vertical ocular refraction (VOR) and spherical equivalent (SE) (rho = 0.96), further supporting generalizations made from nonhuman primate vision studies to human beings.