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.