Optic Nerve Hypoplasia (ONH)

The optic nerve is the nerve that carries electrical signals from the back of the eye to the brain for image processing. Optic nerve hypoplasia is when the optic nerve does not develop properly during development of the baby in pregnancy. It commonly occurs in both eyes but may affect just one eye. It is one of the most common causes of visual impairment in children.

The exact cause of optic nerve hypoplasia has still not been identified. It has been strongly suggested that there is an increased risk of optic nerve hypoplasia occurring in maternal diabetes, maternal alcohol and drug abuse, maternal use of anti-epileptics and an early maternal age (20 years or younger). It may occur by itself or in conjunction with other hormonal or neurological conditions.

The diagnosis of optic nerve hypoplasia is made by an ophthalmological examination of the back of the eye. Typically, the optic nerve will look smaller and paler than expected.

How it affects vision

Children with ONH may have:

• Nystagmus (involuntary eye movements) and reduced vision in both eyes
• Reduced depth perception
• Mild sensitivity to light
• Abnormal visual fields

Prognosis

Optic nerve hypoplasia is a stable condition and vision does not deteriorate over time. Visual impairment ranges from completely normal visual acuity to the inability to see light. Vision may improve in the first few years of life as the brain develops but final visual acuity is difficult to predict. 

Treatments that may be available

There are currently no medical or surgical treatments available for ONH. Children with severe visual impairment should be referred to a low vision aid specialist early on.