Abstract
Although myopia has consistently been associated with near work, human studies have not been able to identify the extent to which the visual environment affects refractive development, to isolate the critical aspects of nearwork that induce ocular changes, or to determine the physiological mechanisms that mediate environmental influences on refractive development. However, recent animal studies have begun to provide answers to many questions concerning the role of vision in refractive development. In particular, in many animals emmetropization has been shown to be an active process that is regulated by optical defocus. This body of evidence suggests that spectacle lenses should influence the ocular development of humans and that it should be possible to devise optical treatment strategies for slowing the progression of myopia. However, to date there is little direct evidence that spectacles can influence refractive development in humans. This presentation will summarize some of the optical performance properties of the emmetropization process in non-human primates and will examine a number of possible explanations for the paucity of data that supports the idea that spectacle lenses, by altering the eye's effective refractive error, can predictably alter human refractive development.