SEX-DIFFERENCES IN CHICK EYE GROWTH AND EXPERIMENTAL MYOPIA

Stimulated by reported sex differences in eye size and refraction in h umans, we compared refractions and ocular size measurements of male an d female chicks. Chicks were reared under a 12-hr light/dark cycle wit h one eye open and the other occluded by a goggle or lid suture, each well-established means of inducing ipsilateral myopia. While the open eyes of the two sexes emmetropized equally well, both ultrasound and c aliper measurements demonstrated that on average males have larger eye s. Although statistically significant for defined populations, the sex differences in open eyes were too small to be diagnostic for individu al birds. The visually-deprived eyes of male chicks were more reactive than those of females, especially following deprivation by a goggle. Consistently, the anterior chamber of visually-deprived eyes of males was deeper than those of the females regardless of the means of impair ing vision. With a goggle, males also developed more myopia and a deep er vitreous chamber than females similarly occluded. When goggles were removed, rapid recovery occurred in 2 weeks irrespective of sex. (C) 1995 Academic Press Limited