LOCAL OCULAR COMPENSATION FOR IMPOSED LOCAL REFRACTIVE ERROR

Abstract-Chicks were raised in a lowotiling environment o ftnd out if their eye growth could compensate for locally imposed hyperopic refractive errors. These chicks became sckctivcly more myopic in the upper visual field than chicks raised in a high-ceiling environment. The vitreous chamber in the low-ceiling birds showed a selective longation in the ventral region that was not seen in the eyes of the high-ceiling birds. This rno~holo~~l difference was small, but probably adequate to aocount for the additional myopia in the low-ceihng birds. These results am consistent with the idea of a visually mediated growth mechanism regulating the local refractive state across the entire visual field so that it matches tbc customary viewing conditions. Such a mechanism might account for the tinding of Fitzke, Hayes, Hodos, Holdcn and Low (Journd of Physiology, London, 369, 3344, 1985) that the refractive errors in the lower field am exactly appropriate for focusing the image of the ground on the retina. Myopia Birds Eye growth “Ramp retina