Effect of dark-rearing on experimental myopia in monkeys.

When lids are surgically fused in rhesus monkeys before eye growth is completed, a high degree of myopia develops, which is caused by an elongation of the eye globe. The present study shows that in monkeys raised in the dark after monocular lid fusion, refraction and axial length were normal in both the closed and the open eye. Myopia, however, readily developed and the eye elongated when a monkey raised in the dark was transferred to illuminated quarters. These findings indicate that visual stimulation through the translucent lids was necessary for the development of this experimental ametropia.