Local Retinal Regions Control Local Eye Growth and Myopia

In chicks, visual deprivation leads to myopia and enlargement of the vitreous chamber of the eye. When chicks were raised with white translucent occluders over their eyes so that either the nasal half, the temporal half, or all of the retina was visually deprived, the resulting myopia (median = -15 diopters) was limited to the deprived part of the retina, regardless of which half of the retina was visually deprived; the nondeprived part remained nearly emmetropic. Correspondingly, the vitreous chamber was elongated only in the region of the visual deprivation, resulting in eyes with different asymmetric shapes depending on which retinal region was deprived. These results argue for a local regulation of ocular growth that is dependent on vision and suggest a hypothesis to explain the epidemiological association of myopia in humans with large amounts of reading. Because most nonfoveal retinal neurons have large receptive fields, they cannot resolve the individual letters on the printed page; this may lead to their activity being less during reading than during most other forms of visual stimulation. Thus, the impoverished stimulus situation of reading may lead to myopia, as do other types of visual form deprivation.