Optic Nerve Hypoplasia (ONH)
Optic Nerve Hypoplasia refers to the underdevelopment of the optic nerve during pregnancy. The dying back of optic nerve fibers as the child develops in utero is a natural process, and ONH may be an exaggeration of that process. ONH may occur infrequently in one eye (unilateral) but more commonly in both eyes (bilateral). ONH is not progressive, is not inherited, and cannot be cured. ONH is one of the three most common causes of visual impairment in children.
In most cases there is no known cause of ONH. Infrequently ONH has been associated with maternal diabetes, maternal alcohol abuse, maternal use of anti-epileptic drugs, and young maternal age (20 years of age or less), but these factors account for very few of the total number of cases. All races and socio-economic groups seem to be affected by ONH.
ONH may occur by itself or along with neurological or hormonal abnormalities. Hormonal problems not apparent in early life may appear later.
Children with ONH demonstrate a wide spectrum of visual function ranging from normal visual acuity to no light perception. The effect on the visual field may range from generalized loss of detailed vision in both central and peripheral fields (depressed visual fields) to subtle peripheral field loss.
A high percentage of children with ONH have associated involuntary rhythmic movements of the eye (nystagmus). In most cases, the nystagmus is associated with significant bilateral reduced visual acuity.
ONH is a stable condition. Visual function does not deteriorate with time. A mild improvement in visual function may occur as the result of maturation processes of the brain. In some cases, reduced nystagmus may also occur.
Depth perception may be more severe is vision loss is great. Mild light sensitivity (photophobia) may occur.
More information is available from our publication A Unique Way of Learning: Teaching young children with Optic Nerve Hypoplasia.
Additional information is available in the Blind Children’s Center Pediatric Visual Diagnosis Fact Sheets.