Eye enlargement in birds induced by dim light.

We here report changes in eye weight and other measurements, in chickens reared in dim light. These effects are distinguished from those seen in light-induced avian glaucoma (brought on by exposure to continuous light). We confirm and extend the results of Berkovitz and Harrison on the dim light effect, but we differ from Axmith and Morin, who were apparently unable to reproduce light-induced avian glaucoma. We cannot yet offer an explanation as to the mechanism(s) of eye damage in either light-induced avian glaucoma or dim light-induced macrophthalmos.