What is Optic Nerve Hypoplasia?
Optic nerve hypoplasia (ONH) is a congenital abnormality where the optic nerve is small and underdeveloped. Since the optic nerves function to carry the visual signal to the brain, their underdevelopment can result in vision impairment.
What causes ONH?
In most cases, a definite cause for ONH is never found. In some cases the underdevelopment may be associated with maternal diabetes, maternal alchohol or drug use during pregnancy, maternal use of some epilepsy drugs during pregnancy, or young maternal age. Some times ONH can be associated with other mid-line brain developmental disorders, such as septo-optic dysplasia. Because of this, further investigation may be needed including an MRI of the brain or evaluation of pituitary function with a pediatric endocrinologist.
How is ONH diagnosed?
ONH is diagnosed by the appearance of the optic nerve during a dilated eye exam. Children may have been referred to the pediatric ophthalmologist to get an exam due to poor vision or another abnormal eye finding. The diagnosis may be confirmed with an MRI scan in some cases.
How does ONH affect vision?
The appearance of the optic nerve does not necessarily predict the severity of associated vision loss. Vision can range from nearly normal all the way to completely blind in an affected eye. The vision loss is typically stable and sometimes may even improve a little with age. Nystagmus (eye shaking) is common in optic nerve hypoplasia, especially if bilateral, and may also limit best vision to some degree. Strabismus (eye misalignment) is also more common.
Is there treatment for ONH?
At this point there is no known effective treatment for ONH itself. If there is a component of vision loss from another cause, such as amblyopia, than part time patching of the better seeing eye may gain some improvement. Full time wear of protective safety glasses is imperative for protection of the better seeing eye if there is significant vision loss in the other. A low vision evaluation would be beneficial for patients with poor vision in both eyes. Stem cell treatments for ONH, as are done in some foreign countries, have not been proven effective and have significant cost and safety concerns.