The Doctor Is In: Optic Nerve Hypoplasia by Lisa Verderber, M.D. Pediatric Ophthalmologist
Reprinted from the Sept./Oct. 1996, issue of VIPS, the newsletter of the Visually Impaired Preschool Services of Louisville, Kentucky.
Optic nerve hypoplasia is a congenital condition in which the optic nerve has not developed properly; it is too small. 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. Depending on the size and abnormality of the hypoplastic nerve, the vision can range from 20/20 to complete blindness, or no light perception. 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. In children with one hypoplastic nerve, the problem is usually manifest by esotropia, or turning in of the affected eye. Especially if the one eye is affected, it is very important to see that all refractive errors are corrected. Optic nerve hypoplasia has been associated with astigmatism. Amblyopia can further reduce vision if one eye has better acuity than the other. In other words, the eye with the poorer vision may be poor in part due to amblyopia. The "stronger" eye becomes the dominant eye, and vision does not develop in the weaker eye because of this dominance. Amblyopia can be treated, and thus a trial of this type of treatment may be considered. Optic nerve hypoplasia is often associated with other brain abnormalities which range from subtle to severe. One common association is with the pituitary gland. The pituitary gland secretes many hormones important for growth. Pituitary dwarfism has been associated with optic nerve hypoplasia. Your pediatrician will follow your child's growth and development carefully in order to determine if there is a problem with the growth hormone or any other hormones. Almost half of all patients with optic nerve hypoplasia have a problem with the cerebral hemispheres. Again, this may result in a very subtle problem, or it may be a severe problem which may further interfere with vision. Like most congenital malformations, there is no clear hereditary pattern to optic nerve hypoplasia, but it is commonly associated with some conditions such as maternal diabetes, and also with other eye conditions such as albinism and aniridia.
Dr. Verderber recently joined the practice of Mahl and Associates Eye Care Centers, in Louisville. She completed her residency in Pediatric Ophthalmology at the Children's National Medical Center in Washington, D.C.