Effect of nearwork-induced transient myopia on distance retinal defocus patterns

The purpose of the current study was to assess the effect of nearwork-induced transient myopia (NITM) on retinal defocus patterns during distance viewing. An empirically derived, conceptual model of human blur perception and related retinal defocus patterns has been extended to determine the effect of NITM on the relative contributions of myopic and hyperopic retinal defocus during distance viewing. Under the normal hyperfocal refractive condition during distance viewing with isolated stimulus conditions, there is very small myopic defocus (approximately 0.25 diopters), and no hyperopic defocus, present. After sustained nearwork generating NITM, a moderate increase in this myopic defocus contribution takes place. In the normal isolated distance viewing situation with only very small myopic defocus present, as would occur with many far outdoor activities, the paucity of overall retinal defocus may provide a "protected" condition against myopia development. In contrast, with the addition of NITM producing increased myopic retinal defocus only, there is an imbalance of retinal defocus that may be myopigenic, especially in the context of foveal and peripheral retinal interactions.