The eye including the optic nerve is an extension of the brain. It is not surprising, therefore, that abnormalities of either structure is often associated with anomalies in the other. Hypoplasia is the term applied to a body part that is not fully developed and that is the case when the optic nerve is abnormally small.
An underdeveloped optic nerve may be present in one eye or bilaterally. When found in both eyes, the pituitary gland is often abnormal as well in which case patients may have low blood sugar or abnormal levels of adrenal hormones. These may be life-threatening and such conditions require careful monitoring. Other brain abnormalities are often found on MRI images. Vision is always reduced in eyes with small optic nerves, sometimes severely. Many patients have ‘dancing eyes’ (nystagmus) and some have crossing of the eyes (strabismus).
This condition is sometimes lumped with de Morsier syndrome but the latter is caused by a different gene mutation.
This condition is caused by a mutation in a gene and is inherited in an autosomal dominant pattern. Few families have been reported and these have had a vertical pattern of transmission through successive generations.
Only an ophthalmologist can make this diagnosis but an MRI and an endocrinological evaluation should be obtained. Lifespan is normal. Low vision aids and mobility training can be helpful to patients.