Exophoria's a form of heterophoria in which there's a tendency of the eyes to deviate outward. Prevalence Exophoria's particularly common in infancy and childhood, and increases with age. Cause Exophoria can be caused by several factors, which include: Refractive errors - distance and near deviation approximately equal. Divergence excess - exodeviation's more than 15 dioptres greater for distance than near deviation. Convergence insufficiency - near exodeviation greater than distance deviatio… (More on Exophoria)