A more negative refractive error, longer axial length, and more hyperopic relative peripheral refractive error in addition to faster rates of change in these variables may be useful for predicting the onset of myopia, but only within a span of 2 to 4 years before onset. Becoming myopic does not appear to be characterized by a consistent rate of increase in refractive error and expansion of the globe. Acceleration in myopia progression, axial elongation, and peripheral hyperopia in the year prior to onset followed by relatively slower, more stable rates of change after onset suggests that more than one factor may influence ocular expansion during myopia onset and progression.

No abstract

Despite protective associations previously reported for time outdoors reducing the risk of myopia onset, outdoor/sports activity was not associated with less myopia progression following onset. Near work also had little meaningful effect on the rate of myopia progression.

Substantive and consistent elevations in accommodative lag relative to model estimates of lag in emmetropes did not occur in children who became myopic before the onset of myopia or during the year of onset. Increased accommodative lag occurred in children after the onset of myopia. Elevated accommodative lag is unlikely to be a useful predictive factor for the onset of myopia. Increased hyperopic defocus from accommodative lag may be a consequence rather than a cause of myopia.

Before myopia onset, near work activities of future myopic children did not differ from those of emmetropes. Those who became myopic had fewer outdoor/sports activity hours than the emmetropes before, at, and after myopia onset. Myopia onset may influence children's near work behavior, but the lack of difference before onset argues against a major causative role for near work. Less outdoor/sports activity before myopia onset may exert a stronger influence on development than near work.