Figure 1. Mean ocular difference (Experimental – Fellow eye) of refractive error and axial length properties of chick eyes following various periods of lens wear [minus lenses (−10D), plus lenses (+10D), or No Lens (NL) groups]. Note that substantial axial length changes and refractive error developed within the first two days of lens wear. Minus lens wearing eyes showed more rapid changes in axial length in comparison to plus lens wearing eyes. Note also that the refractive compensation to plus lenses was maximal after 4 days; whereas, minus lens-wearing eyes continued to become more myopic over the 7 days examined.