The optic nerve serves as a connector, carrying visual information from the eye to the brain. Those that have optic nerve hypoplasia (ONH) have an underdeveloped optic nerve in one or both eyes. Typically each optic nerve has about 1 million connections. However, those with optic nerve hypoplasia have far fewer connections. Optic nerve hypoplasia is one of the three most frequently diagnosed visual impairments in children in the United States.
Often associated with optic nerve hypoplasia are hormonal deficiencies. Therefore, it is critical for a child to be seen by an endocrinologist at the time of diagnosis and then followed up regularly as hormonal deficiencies can develop at any time. The ophthalmologist may also recommend an MRI and/or CT to check for any brain abnormalities, which are also associated with ONH. In some cases children have a poorly formed or missing septum pellucidum (area in the brain that divides the ventricles). This is referred to as septo-optic dysplasia (SOD) or DeMorsier’s syndrome. Other areas of the brain may also be affected.
Optic nerve hypoplasia is a congenital defect. It is thought that there may be an exaggeration of the natural dying of nerve fibers as the child develops in utero. For the majority of cases there is no known cause for why this condition occurs. A few cases have been associated with young maternal age (under 20 years of age), maternal diabetes, maternal alcohol use, and maternal anti-epileptic drug use. ONH affects all races and socio-economic groups.