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SYMPTOMS
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Decrease in vision, Visual field defects
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May experience a further decrease in vision and/or metamorphopsia in the presence of macula involvement
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SIGNS
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Typically bilateral
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Large disc that is partially or completely excavated inferiorly with a glistening white appearance (superior rim is typically intact), Peripapillary pigmentary changes (Hypopigmentation present more so than hyperpigmentation), Possible macular involvement (Sensory retinal detachment at the macula, Choroidal neovascular membrane)
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Optic nerve colobomas can be associated with Other ocular colobomas, Posterior lenticonus, Remnants of the hyaloid artery, Posterior embryotoxon
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WORK-UP
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Pupils (presence of an APD if optic nerve coloboma is unilateral or asymmetric), EOMs, Cover test (strabismus may be present), Full eye exam with dilation, Visual field, OCT of the optic nerve, OCT of the macula (may present with a sensory retinal detachment at the macula or choroidal neovascular membrane), OCT-Angiography, Fundus Autofluorescence, Fluorescein Angiography, Indocyanine Green Angiography, Fundus photos, Electrodiagnostic testing (VEP), Watzke-Allen test, Macular photostress test, Amsler grid
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TREATMENT
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Give take home Amsler grid in order to monitor for macula involvement
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Optic nerve coloboma with no macular involvement: Monitor. No treatment is needed
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Optic nerve coloboma with macular involvement (sensory retinal detachment at the macula or choroidal neovascular membrane): Refer to a retinal specialist ASAP for further evaluation and treatment (treatment is typically not successful due to the high rate of recurrence)
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Refer patient to a pediatrician and pediatric neurologist as these patients commonly have neurologic and systemic abnormalities
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If the patient has poor vision, refer to low vision
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FOLLOW-UP
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If monitoring, the patient should be seen back in 6-12 months
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After patient is evaluated and treated by a retinal specialist and the retina/macula is stable, the patient should be seen back every 6 months
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ADDITIONAL LAB | TESTS
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Genetic testing: PAX2
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Rule out the following syndromes that can be associated with optic nerve colobomas (30% of the time):CHARGE syndrome, Branchio-oculo-facial syndrome, First arch syndromes, Fraser syndrome, Amniotic band syndrome, Aicardi syndrome, Renal-coloboma syndrome
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ETIOLOGY
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Developmental optic nerve dysplasia (occurs due to incomplete closure of the embryonic fissure)
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Can be sporadic or autosomal dominant in terms of inheritance (mutation of the PAX2 gene)
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DIFFERENTIAL DX
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Morning glory disc, Optic nerve pit, Posterior staphyloma
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NOTES
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Optic nerve colobomas are usually an isolated anomaly
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Optic nerve colobomas can be associated with myopia and/or strabismus
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Optic nerve colobomas are typically located inferiorly and can also involve the retina and choroid
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