Animal research has established that signals derived from both contrast and defocus can influence refractive development, likely concurrently, so that overall refractive development reflects an integration of these primary visual signals. Important findings include the association of L/M opsin mutations with familial high myopia, axial hyperopia produced in response to form deprivation in moderate outdoor lighting levels, effective control of myopia by diffusion optics technology spectacle lenses designed to reduce retinal contrast, and all current defocus-based optical treatments which inadvertently reduce image contrast. In this review, clinical trial results of optical myopia treatment strategies that manipulate retinal contrast are considered in context of animal research outcomes. In conclusion, research suggests mild reductions in retinal contrast can slow myopia progression in children and may also have a role in defocus-based optical therapy.

Myopia; Axial length, eye; Refraction, ocular; Retinal contrast; Defocus