Form deprivation myopia in mature common marmosets (Callithrix jacchus)

PURPOSE. Experimental manipulations of visual experience are known to affec t the growth of the eye and the development of refractive state in a variet y of species including human and nonhuman primates. For example, it is well established that visual form deprivation causes elongation of the eye and myopia. The effects of such manipulations have generally been examined in n eonatal or juvenile animals. Whether adolescent common marmosets (a new wor ld primate) are susceptible to form deprivation myopia was studied. METHODS. Five adolescent marmosets were used in this study. Monocular form deprivation was induced by lid closure for 12 to 20 weeks, starting between 299 and 315 days of age. The effects of deprivation were assessed with ker atometry, A-scan ultrasonography, and cycloplegic refractions. Both eyes (t reated and fellow control);were measured before lid-closure, at the end of the deprivation period, and several times over the following 8 to 12 weeks. RESULTS. Adolescent marmosets are susceptible to visual form deprivation my opia. The experimental eyes showed significant axial elongation and myopia relative to the fellow control eyes. These changes were smaller, however, t han those observed in younger eyes deprived for comparable periods. Like ju venile animals, the adolescent marmosets did not show recovery from myopia over the period monitored. CONCLUSIONS. The period for susceptibility to form deprivation myopia in th e marmoset monkey extends beyond the early developmental period when ocular growth is rapid and emmetropization normally takes place. Visual form depr ivation in adolescent marmosets with adult-sized eyes results in increased ocular growth and myopia. These data suggest that visual factors may influe nce the growth and refractive development of the human eye after puberty an d may be involved in late-onset myopia.