Pediatric Ophthalmology

150 8 Congenital Abnormalities of the Optic Nerve

OPTIC DISC COLOBOMA

Signs ● White, bowl-shaped excavation that occurs in an enlarged optic disc. The excavation is decentered inferiorly and the superior neu roretinal rim is relatively spared. In case of complete excavation of the entire disc, the excavation is deeper inferiorly. ● Chorioretinal coloboma can be associ ated—if so, microphthalmia is frequently present. ● Iris and ciliary body colobomas often coexist. ● Rhegmatogenous or serous RD may de velop in some patients—rhegmatogenous detachment is often associated with chorio retinal coloboma, whereas serous detachment is more common in case of isolated optic nerve coloboma. ● Associated conditions may include the following: ■ CHARGE association: coloboma, cho anal atresia, congenital heart disease, and multiple other abnormalities ■ Walker-Warburg syndrome ■ Goltz focal dermal hypoplasia ■ Aicardi syndrome ■ Goldenhar sequence ■ Linear sebaceous nevus syndrome ■ Dandy-Walker malformation ■ Renal coloboma syndrome—with a mu tation of PAX2 transcription ■ Microphthalmia—in case of chorioreti nal involvement Differential Diagnosis ● MGDA ● Peripapillary staphyloma

● Clearly demarcated bowl-shaped excava tion of the optic disc, which is typically de centered and deeper inferiorly ● Unlike the morning glory disc, it has no central glial tuft and the disc vasculature is usually normal. ● Unilateral and bilateral optic disc coloboma occurs with similar frequencies. ● Occasionally, involvement of the entire disc occurs. ● Other types of uveal coloboma can coexist. ● They may be isolated or part of a systemic ● Thought to result from incomplete or ab normal fusion of the two sides of the proximal end of the embryonic fissure ● Most cases are sporadic but may be au tosomal dominant, autosomal recessive, or X-linked recessive. ● A wide variety of mutations have been doc umented in patients with coloboma— CHD7 mutation is associated with 60% of cases of CHARGE ( c oloboma of the eye or central nervous system anomalies, h eart defects, a tre sia of the choanae, r etardation of growth or development, g enital or urinary defects, and e ar anomalies or deafness) syndrome. Symptoms ● Visual acuity may be mildly or severely decreased in one or both eyes—the degree of foveal involvement by the coloboma is the only feature that relates to visual outcome. syndrome. Etiology

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