(BQ) Part 2 book “Color atlas & synopsis of clinical ophthalmology pediatric ophthalmology” has contents: Congenital abnormalities of the optic nerve, retinal anomalies, eyelid anomalies, lacrimal anomalies, strabismus disorders. | CHAPTER 7 Congenital Abnormalities of the Optic Nerve Aldo Vagge and Leonard B. Nelson ■ OPTIC NERVE HYPOPLASIA Optic nerve hypoplasia (ONH) is a congenital, 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 central nervous system (CNS) abnormalities. ONH may be unilateral or bilateral (80%) and may be asymmetric. Most common congenital optic disc anomaly Optic nerve aplasia is rare. No pupillary light reflex and absence of the optic disc, nerve fiber layer, and retinal blood vessels on examination. Etiology Not completely understood Parental drug and alcohol abuse contributes to an increasing prevalence of ONH. Drug associations include exposure to carbemazepine, 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 segmental 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-opto dysplasia 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 unilateral ONH. Signs Range of visual acuity is 20/20 to no light perception since vision is determined primarily by the integrity of the papillomacular nerve fibers more than the overall size of the disc. Amblyopia as a result of accompanying strabismus and anisometropia Nystagmus: often develops at 1 to 3 months of age in bilateral cases Strabismus may be associated with unilateral ONH. Afferent pupil defect in asymmetric or unilateral cases Visual fields (VFs) often have localized defects as well as general constriction. Abnormally .
