CLOCK and myopia: To test the role of circadian rhythms, we investigated the morphological and refractive effects of clock gene disruption on optical development, using two widely separated species commonly used for circadian studies: mice, a vertebrate increasingly used to address the mechanisms of myopia; and Drosophila melanogaster, an organism frequently used to dissect the molecular genetics and physiology of the visual system but not yet applied to study mechanisms of refractive disorders.