Form deprivation myopia in adolescent monkeys

Background. Early in life, at ages corresponding to the rapid infantile pha se of ocular growth in humans, visual feedback can modulate refractive deve lopment in monkeys and many of her species. To determine if vision-dependen t mechanisms can still influence refractive development in primates during the slow juvenile phase of ocular growth, the time period when myopia typic ally develops in human children, we examined the effects of form deprivatio n on adolescent monkeys. Methods. Unilateral, form deprivation was produced in four rhesus monkeys by surgically fusing the eyelids of one eye. The on set of deprivation was between 3.7 and 5 years of age, which corresponds to onset ages between approximately 15 and 20 human years. The ocular effects of form deprivation were assessed by cycloplegic retinoscopy and A-scan ul trasonography. Results. At the onset of form deprivation all four monkeys w ere isometropic and the axial dimensions in the two eyes were well matched. After 71 to 80 weeks of form deprivation, all of the deprived eyes had bec ome relatively more myopic than their fellow non-treated eyes (mean anisome tropia = -2.03 +/- 0.78 D) and they exhibited relative increases in vitreou s chamber depth (mean = 0.55 +/- 0.31 mm) and axial length (mean = 0.49 +/- 0.35 mm). Discussion. Our results demonstrate that vision-dependent mechan isms can influence ocular growth and refractive development in "teenage" mo nkeys. These results raise the possibility that visual experience may be in volved in the genesis of school-age myopia in children.