DIFFERENCES IN EYE GROWTH AND THE RESPONSE TO VISUAL DEPRIVATION IN DIFFERENT STRAINS OF CHICKEN

Several laboratories studying visual deprivation myopia in the domesti c chick report varying degrees of axial elongation and myopia induced by similar visual deprivation techniques. In this study rye tested the hypothesis that in different strains of chick the eyes respond differ ently to visual deprivation. We compared under identical conditions tw o strains of White Leghorn chick commonly used in ocular development r esearch-the Cornell-K strain (K) and Washington H and N Strain (H/N). The normal development of the eye was found to vary significantly betw een these strains of White Leghorn chicks. The K strain normally devel ops flatter corneas, thicker lenses, and larger eyes than the HIN stra in. The response to visual deprivation also varies significantly betwe en strains. For example, we find that 2 weeks of visual deprivation in the K strain results in less elongation of the vitreous chamber and f lattening of the cornea yielding tower levels of induced myopia compar ed to the H/N strain. Our results show that while visual experience cl early affects normal ocular development in both strains of chick, the nature of the effect depends upon not only the type and duration of th e experience but the genetics of the subject population as well.