Common vision problems in children include strabismus, amblyopia, refractive error and visual deprivation. Strabismus refer to children's sight are inconsistent when they see things, eyeballs are unable to rotate in the same direction, common strabismus are esotropia and exotropia. Amblyopia refers to one or both eyes have poor vision, even after correction, it can not amount to the vision which should be achieved at this age. Refractive error refers to uncorrected visual acuity can not reach to the normal standard. It includes myopia, hyperopia and astigmatism. Visual deprivation refers to congenital cataract, congenital ptosis, etc, thus the visual function is not well developed.