In an infant with subnormal vision for age, consider several general categories: a structural basis for visual impairment (eg, optic nerve hypoplasia, congenital cataracts), an inherited retinal dystrophy/degenerative process, cortical visual impairment, or delayed visual maturation. Features that support a diagnosis of septo-optic dysplasia include absent septum pellucidum, dysgenesis/agenesis of the corpus callosum, and pituitary abnormalities.