Pediatric Ophthalmology

OPTIC NERVE HYPOPLASIA 145

Signs ● Range of visual acuity is 20/20 to no light perception since vision is determined pri marily by the integrity of the papillomacular nerve fibers more than the overall size of the disc. Visual acuity in affected subjects does not necessarily correlate with the size of the optic nerve head. ● Amblyopia as a result of accompanying stra bismus and anisometropia ● Nystagmus: often develops at 1 to 3 months of age in bilateral cases ● Strabismus may be associated with unilat eral ONH. ● Afferent pupil defect in asymmetric or uni lateral cases ● Visual fields (VFs) often have localized de fects as well as general constriction. ● Abnormally small optic nerve head, often gray or pale in color with “double-ring sign” (scleral canal surrounds a small optic nerve; Fig. 8-1 ) ● Superior segmental hypoplasia of the optic nerve is a segmental form of ONH occur ring in some children of insulin-dependent mothers. ● Retinal vascular tortuosity and a failure of the normal arcade pattern are important but inconsistent signs. ● Associated conditions may include the following: ■ ONH may be associated with other ocular disorders such as microphthalmia, aniridia, and albinism; systemic association especially with neurologic and endocrine anomalies and many syndromes. ■ Endocrine dysfunction: Approxi mately half of patients with ONH have hypopituitarism. Patients are at risk for hypothalamic and pituitary dysfunction such as growth hormone deficiency (most

common), hypothyroidism, hyperprolac tinemia, panhypopituitarism, and diabetes insipidus. ■ Neurologic anomalies are detected by neuroimaging in 60% of bilaterally affected patients and ~30% of unilateral ONH. Hy poplastic optic nerves and chiasm, cortical heterotopia, hydrocephalus, and absent or hypoplastic corpus callosum and absent septum pellucidum are the more common associated anomalies. ■ SOD is a less common finding, diag nosed with two or more of the following features: ONH, midline brain defects (such as agenesis of the corpus callosum and absence of the septum pellucidum) and pituitary hypoplasia. ■ Developmental delay more common in patients with bilateral ONH, highly cor related with corpus callosum hypoplasia and hypothyroidism Differential Diagnosis ● Optic nerve atrophy ● Optic nerve coloboma ● Tilted disc syndrome (TDS) ● Glaucoma Diagnostic Evaluation ● Optical coherence tomography (OCT) useful to evaluate thin nerve fiber and gan glion cell layers ● Ocular electrophysiology: Electroretino gram (ERG) finding is normal in ONH, visually evoked potentials (VEP) may be de layed in amplitude and implicit times. ● Magnetic resonance imaging (MRI) to rule out CNS malformations ● Pediatric endocrinologist referral is rec ommended. Pediatrician should follow up growth chart for endocrine changes. Undiag nosed endocrine deficiencies lead to risk of

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