The long term goal of these studies is to identify effective preventive or management strategies for disorders of refractive status (i.e. myopia). Myopia (nearsightedness), a clinical condition in which the eye grows too long in relation to the refractive power of its optical components, is the most common ophthalmic disorder in the world. Its economic and public health impact are tremendous (Americans alone spend nearly 2 billion dollars for refractive error correction each year). A scientific debate has existed for over a century about whether the refractive status (e.g. nearsighted, farsighted) of the eye can be influenced by its visual input. Converging evidence from clinical studies and animal models has shown that the refractive development of the eye is influenced by visual experience. What has yet to be determined, however, is the nature of the signal that is used to regulate eye growth. As a first step, normal eye growth was determined using 237 norma lly reared monkeys, whose ages ranged from birth to 5 years (young adult). The data supported a role for both genetics and environment in the regulation of emmetropization (i.e. the process of normal eye growth and refractive development). These baseline data were then used to examine the development of the untreated eyes of 15 monkeys reared with one of 3 different visual manipulations of the fellow eyes. Despite having normal visual input, the untreated eyes differed systematically in refractive error and axial length, according to the treatment received by their fellow eyes. Thus, we have established that future models of eye growth will have to consider not only the direct influence of visual input on that eye, but also the indirect influence of the visual input to the fellow eye. In an effort to study this further, a unique helmet and goggle design was created to rear four monkeys with improved visual manipulations. Of those, three were reared with unequal binocular input (defocused in put of one eye, light input only or no light input of the fellow eye). While these data provided new evidence for an interocular influence in the regulation of emmetropization, they also support the notion that rather than simply trying to "match" the two eyes in physical length or refractive status, the interocular influence may in fact be sensitive to the quality of the visual input. FUNDING NIH RR00165 $50,000 7/01/95 - 6/30/99 PUBLICATIONS Bradley, D.V., Fernandes, A., Lynn, M., Tigges, M. and Boothe, R.G. Emmetropization in the rhesus monkey (Macaca mulatta) Birth to young adulthood. Invest. Ophthalmol. Vis. Sci. (In press). P51RR00165-38 1/1/98 - 12/31/98 Yerkes Regional Primate Research Center