Optic nerve (CN II)
Focused guidance for emergency assessment and initial management of optic nerve pathology relevant to maxillofacial and dental practice. Emphasises rapid, objective assessment, recognition of red flags, timely imaging, and urgent referral pathways.
Anatomy and localisation
The optic nerve transmits retinal signals to the visual cortex. Fibres leave the globe at the optic disc, pass posteriorly through the orbit and optic canal to the chiasm; nasal retinal fibres decussate at the chiasm, temporal fibres remain ipsilateral. Lesion location produces characteristic field defects:
- Pre‑chiasmal (optic nerve): monocular visual loss.
- Chiasmal: bitemporal hemianopia.
- Post‑chiasmal (optic tract/radiations/occipital): homonymous hemianopia (contralateral).
Why this matters in maxillofacial practice
Facial and orbital trauma, orbital infections, expanding masses, iatrogenic injuries and certain drugs/toxins can rapidly threaten vision. Emergency clinicians must identify sight‑threatening presentations, document baseline function, expedite imaging, start empiric treatment where appropriate, and arrange urgent ophthalmology/neurology/neurosurgery input.
Typical presentations and red flags Common ED presentations:
- Acute monocular vision loss (painless or painful).
- Subacute progressive visual loss over days-weeks.
- Reported visual field loss or “missing” areas.
- Eye pain on movement (suggests optic neuritis).