Pediatric Ophthalmology

CHAPTER

Congenital Abnormalities of the Optic Nerve 8 ■ Aldo Vagge and Leonard B. Nelson

OPTIC NERVE HYPOPLASIA

carbamazepine, isotretinoin, phenytoin, quinine, and valproic acid. Young maternal age and maternal insulin-dependent diabetes have also been implicated in some cases (associated with subtype—superior segmen tal optic hypoplasia). Genetics ● Most cases are sporadic. ● Bilateral ONH is inherited in an autosomal dominant pattern based on the few families reported. Mutation in the PAX6 (11q13) gene is responsible. ● Mutation in the HESX1 gene has been identified in sporadic septo-optic dysplasia (SOD) and pituitary disease. ● Mutation in the TUBA8 gene is associated with polymicrogyria and ONH. Symptoms ● Decreased vision in one or both eyes ● Strabismus may be associated with unilat eral ONH. ● Color vision and other visual functions may remain unaffected.

● Optic nerve hypoplasia (ONH) is a congeni tal, nonprogressive developmental abnormality in which the optic nerve is smaller than usual because of reduced numbers of retinal ganglion cells. It is frequently associated with other cen tral nervous system (CNS) abnormalities. ● ONH may be unilateral or bilateral (80%) and may be asymmetric. ● Most common congenital optic disc anom aly. Accounts for up to 25% of children with significant congenital visual loss. The estimate prevalence is 1.5 per 10,000. ● Optic nerve aplasia is rare. No pupillary light reflex and absence of the optic disc, retinal nerve fiber layer (RNFL), and retinal blood vessels on examination Etiology ● Not completely understood ● Parental drug and alcohol abuse contrib utes to an increasing prevalence of ONH. Drug associations include exposure to

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