Normally the axes of the two eyes remain parallel to each other in all directions of gaze. Disturbances of this parallelism may occur, resulting in squints. Manifest squints are termed heterotropias. Heterophorias are mal-alignments of the visual axes which are kept latent by fusion mechanisms. The effort to maintain the paralellism in the presence of latent squints causes a strain on the extraocular muscles leading to aesthenopic symptoms such as heaviness of eyes, frontal or occipital headaches, diplopia, and, pain in and around eyes. Visual problems occur during the critical period of visual development. Heterophorias can have long term effects on visual acuity, scholastic performance and quality of life of the child. Various studies have reported a prevalence of heterophorias in children to be between 2.8% to 14.6%. Of these children, the incidence of poor scholastic performance has been reported to be approximately. Timely detection and treatment of heterophorias and associated refractive errors has been shown to ameliorate symptoms of aesthenopia.