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SYMPTOMS
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Usually a decrease in vision (vision can range from normal to no light perception), Scotomas, Visual field defect, Decreased color vision
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SIGNS
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Typically unilateral | Signs at onset of trauma: If trauma involves the posterior aspect of the optic nerve, the optic nerve typically appears normal. If trauma involves the area anterior to the entry site of the central retinal vein and artery, the optic nerve typically appears edematous with retinal hemorrhages
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Signs about 3-6 weeks later: Optic nerve pallor
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Other ocular signs of trauma may be present as well including a subconjunctival hemorrhage, hyphema, torn iris, choroidal rupture, etc.
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WORK-UP
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Cranial Nerve Testing | EOMs | Pupils: Decrease in direct light response, APD in the eye with traumatic optic neuropathy | Color vision: Typically abnormal | Visual field: Variable field loss | Red Cap Test: Reduced color brightness on side of traumatic optic neuropathy
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Slit lamp |Dilated fundus exam | Visual field threshold | OCT of optic nerve | OCT of macula | Visual Evoked Potential (VEP)
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TREATMENT
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If an acute traumatic optic neuropathy, refer to neuro-ophthalmology for further evaluation and possible treatment
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If traumatic optic neuropathy is longstanding, treatment will likely not be beneficial
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Treatment is still controversial | High dose corticosteroids were thought to help but the CRASH study showed the increased risk of mortality in patients taking high dose corticosteroids with a head injury. The International Optic Nerve Study showed no difference in visual outcomes in patients being observed and patients taking high dose corticosteroids.
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Surgery has shown to be somewhat effective in patients with direct trauma especially if bony fragments of the orbit were compressing the optic nerve but not with indirect trauma to the optic nerve.
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FOLLOW-UP
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If traumatic optic neuropathy is longstanding, monitor in 6-12 months
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If patient was referred to neuro-ophthalmology for additional testing or treatment, monitor in 6 months once patient is determined to be stable
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ADDITIONAL LAB | TESTS
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CT or MRI of the orbit and brain (CT scan is typically done before an MRI to check for a metallic foreign body. Also, the CT scan is better in determining orbital and optic canal fractures)
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ETIOLOGY
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Optic nerve damage from ocular or head trauma due to the following reasons: · Mechanical damage to the retinal nerve fiber layer · Ischemia due to damage to the radial peripapillary plexus · Neuron apoptosis
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Trauma to the optic nerve can be direct or indirect (most common)
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Optic nerve head, intraorbital, intracanalicular, or intracranial damage can lead to a traumatic optic neuropathy
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DIFFERENTIAL DX
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Posterior ischemic optic neuropathy, Optic neuritis, Toxic optic neuropathy, Previous CRAO
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NOTES
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Indirect trauma: 40-60% of patients experience visual recovery
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Direct trauma: Poor prognosis. Vision loss is severe and irreversible
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Based on the International Optic Nerve Trauma Study, visual acuity improvement was best seen in patients who were only observed
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