The optic nerve carries visual information from the eye to the brain. If the optic nerve is underdeveloped, adequate visual information does not reach the brain for processing. Optical nerve hypoplasia was once considered a rare condition, but now it is thought to be the most common congenital defect of the optic nerve. Affected eyes also show visual field defects. In other words, part of the visual space, such as the upper or lower half of the normal visual field, may be missing.
Color vision is usually normal in an eye with optic nerve hypoplasia.
This is in contrast to optic nerve injuries that occur later in life. These acquired optic nerve problems often lead to a loss of color vision. Optic nerve hypoplasia may affect either one or both eyes. If both eyes are affected, they may be affected to different degrees. Children with bilateral optic nerve hypoplasia usually present in infancy with poor vision and nystagmus, or shaking of the eyes.