Loss of melanopsin alters refractive development and ocular growth. A) Refractive error measurements in Opn4+/+ (black), Opn4−/− (red), and Opn4DTA/DTA (blue) mice. Opn4−/− mice had a steeper refractive development curve (p<0.001) that led to hyperopia compared to Opn4+/+ mice, with significantly more myopic refractions at earlier ages (p<0.001) and hyperopic refractions at older ages. Opn4DTA/DTA showed significantly more hyperopic refractions than the other two genotypes (p<0.001). B) Shorter axial length (p<0.001) in Opn4−/− mice compared to Opn4+/+ at later ages. Opn4DTA/DTA mice also had significantly shorter axial lengths than Opn4+/+ or Opn4−/− mice across most ages (p<0.001). C) Corneal curvature was not different between Opn4+/+, Opn4−/−, and Opn4DTA/DTA mice (p=0.98) but increased with age (p<0.001). Data are presented as mean ± SEM. Comparisons were performed with RM two-way mixed-effects analysis (MEA) with Holm-Sidak multiple comparisons tests (HSK) where *p<0.05, **p<0.01, and ***p<0.001. Black and red asterisks = significant differences compared to Opn4+/+ and Opn4−/− mice, respectively.