Experimentally induced myopia in chicks: morphometric and biochemical analysis during the first 14 days after hatching.

Application of a translucent goggle over the chick eye on the first day after hatching led to the development of myopia. By the 14th day, the mean refractive error was about -10.0 D. Significant increases in axial and equatorial diameters were observed when the treated eyes were compared with untreated contralateral eyes. The lens did not appear to be affected, either optically or biochemically. A temporal study showed that changes were evident within 2 days of goggle application, and were significantly established 5 days later. Total soluble protein concentrations of the treated and untreated eyes were not significantly different, nor were the dry weights of the sclera and cornea. The enlargement of the eyeball that was observed in the experimental induction of myopia seems due to an increase in fluid within the eye. The data are consistent with the view that refractive properties of the chick eye are dependent upon the clarity of the visual image and modulation of these features occurs after hatching.