Eyelid closure effects on the refractive error of the eye in dark- and in light-reared kittens.

Kittens reared in the dark with their eyelids sutured postnatally on one side have developed hypermetropia in the closed eye (average: +2.75 D for the horizontal meridian). This was significantly different (0.01 greater than p greater than 0.005) from the results of the open eye (+1.67 D; 180 degrees). The closed eye of light-reared kittens had similar refractive error (+0.33 D) to that of their open eye (+0.50 D), and to that of kittens light-reared with both eyes open (+0.75 D). Axial length of the closed eye in the dark-reared kittens and its corneal refractive power were smaller in comparison to the results for the open eye. It was concluded that in kittens lid closure during development in the dark induces hypermetropia.