Developmental abnormalities of the optic nerve may or may not limit vision. To maximize visual potential in a child with an optic disc (also called optic nerve head) abnormality, treatment of possible superimposed amblyopia should always be considered.
Optic Nerve Hypoplasia
Optic nerve hypoplasia (ONH), the most common developmental optic disc anomaly, is characterized by a decreased number of optic nerve axons. It can be unilateral, bilateral, or segmental and is often asymmetric if bilateral. The typical affected disc can be pale, gray, and relatively small with vascular tortuosity (Fig 26-1A). A yellow-to-white ring around the disc (corresponding to abnormal extension of retina over the lamina cribrosa), known as the double ring sign, may be present. When the double ring sign is present, the hypoplastic disc–ring complex can be mistaken for a normal-sized optic nerve with normal cup–disc ratio (Fig 26-1B, C).
Visual acuity can range from 20/20 to no light perception. The extent of papillomacular fiber involvement and any associated amblyopia determines visual acuity.
ONH is usually idiopathic and sporadic. It is more prevalent in fetal alcohol syndrome. Segmental ONH may be associated with maternal diabetes mellitus. ONH may be associated with central nervous system (CNS) abnormalities and pituitary gland dysfunction.
Septo-optic dysplasia (de Morsier syndrome) is the association of ONH with absence of the septum pellucidum and agenesis of the corpus callosum (Figs 26-2, 26-3). As isolated abnormalities, these neuroimaging findings are not associated with neurodevelopmental or endocrinologic problems. Cerebral hemisphere abnormalities such as schizencephaly, periventricular leukomalacia, and encephalomalacia occur in approximately 45% of patients with ONH and are associated with neurodevelopmental defects.
Patients with ONH can have pituitary gland abnormalities, which are important to rule out in children who present with ONH. Magnetic resonance imaging (MRI) in affected patients reveals an ectopic posterior pituitary bright spot at the upper infundibulum. This finding is associated with pituitary hormone deficiencies, including growth hormone deficiency, hypothyroidism, hyperprolactinemia, hypocortisolism, panhypopituitarism, and diabetes insipidus. A history of neonatal jaundice suggests hypothyroidism; neonatal hypoglycemia or seizures indicate possible panhypopituitarism. Patients with ONH and hypocortisolism, especially with diabetes insipidus, can have problems with thermal regulation and dehydration and must be monitored carefully during febrile illnesses.
A, Left optic nerve hypoplasia. Note the small, pale disc with vascular tortuosity. B, Left optic nerve hypoplasia with the double ring sign. When viewed quickly, the hypoplastic disc–ring complex may be mistaken for a normal-sized optic nerve. C, The normal right optic disc of the patient shown in part B.
(Courtesy of Arif O. Khan, MD.)
Children with periventricular leukomalacia can have a variant of ONH that may be mistaken for glaucomatous cupping. The optic nerve has a large cup within a normal-sized optic disc secondary to transsynaptic degeneration of optic axons, a consequence of lesions in the optic radiations. This form of ONH is not associated with endocrine deficiencies.
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.