A natural history of vision loss: Insight from evolution for human visual function

•Naturally “blind” animal species reveal the role of visual experience for the functional architecture of the brain.•Blind individuals and blind species share some common attributes of brain organization and sensory experiences that set them apart from the sighted.•A phylogenetic perspective on vision and vision loss provides better translation of research results from animal models to human treatments. Research on the origin of vision and vision loss in naturally “blind” animal species can reveal the tasks that vision fulfills and the brain's role in visual experience. Models that incorporate evolutionary history, natural variation in visual ability, and experimental manipulations can help disentangle visual ability at a superficial level from behaviors linked to vision but not solely reliant upon it, and could assist the translation of ophthalmological research in animal models to human treatments. To unravel the similarities between blind individuals and blind species, we review concepts of "blindness" and its behavioral correlates across a range of species. We explore the ancestral emergence of vision in vertebrates, and the loss of vision in blind species with reference to an evolution-based classification scheme. We applied phylogenetic comparative methods to a mammalian tree to explore the evolution of visual acuity using ancestral state estimations. Future research into the natural history of vision loss could help elucidate the function of vision and inspire innovations in how to address vision loss in humans.