REGULATION OF EMMETROPIZATION

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The role of visual experience on refractive development and eye growth was assessed in newborn and juvenile monkeys, as part of a larger effort to identify the factors that determine whether eyes become nearsighted, farsighted, or have normal vision. The results of the infant monkeys reared with visual occlusion of one eye confirm our assertion that models of eye growth will have to consider not only the direct influence of visual experience on the eye, but also the indirect influence of the visual input provided to the fellow eye. The next step in the series is to determine whether this previously unknown interocular influence is due to a mechanism that serves to match the length of the two eyes, or whether this mechanism is actually sensitive to the visual input of the two eyes. In an effort to simulate the near-work visual demands that occur while reading, juvenile monkeys have been trained on a joystick task in which they track targets on a computer screen. We have d esigned a task that the monkeys are willing to work on for several hours each day; which mimics the high visual demands that are associated with the development of myopia in school-aged children. The next step in this series is to assess the accommodative posture of the monkeys' eyes while they are engaged in this task; once it has been confirmed that they must accommodative for extended periods of time, similar to the time spent by kids who do schoolwork, we will compare their current refractive state with their measurements obtained prior to the "reading" task. The goal of both of these visual manipulations is to identify effective management or prevention strategies for myopia; the most prevalent, and the most costly, visual disorder in the world.