We investigated whether the development of the vertebrate crystalline lens is sensitive to visual input. The optical properties of fish lenses were examined as a function of lens size and the optical rearing conditions. Fish (Haplochromis burtoni, Cichlidae) were reared in white light (control group), under spectral deprivation (monochromatic lights), deprivation of the cone system (scotopic illumination), and complete visual deprivation (darkness). Longitudinal spherical aberrations (LSAs) and refractive index profiles of the lenses were measured with thin laser beams. The performance of the lens was modeled by ray-tracing calculations from measured LSAs. In lenses from the control group, LSA and f/R (focal length relative to lens radius) decreased as a function of age. The optical properties of the lenses were modified after rearing in darkness, scotopic illumination, and in monochromatic lights due to changes in the refractive index profile. Rearing in darkness and scotopic illumination reduced the optical quality of the lens. In animals reared under spectral deprivation, the lens did not create well-focused images for all spectral cone types in the same plane, as it does in animals reared in white light. We conclude that visual input seems to play an important role in the development of the lens. The control mechanisms remain unknown.