Neuro-Ophthalmology and Strabismus
Core concepts
Understand the afferent and efferent visual pathways. Know that optic neuritis causes painful visual loss with a relative afferent pupillary defect and dyschromatopsia; papilloedema is bilateral disc swelling from raised intracranial pressure. Recognise cranial nerve palsies: CN III (ptosis, down-and-out eye, dilated pupil), CN IV (vertical diplopia, head tilt), CN VI (horizontal diplopia, failure to abduct).
Strabismus: know esotropia versus exotropia, comitant versus incomitant, and the cover test. Understand amblyopia and its treatment (patching, refractive correction). Know that a new-onset strabismus in an adult needs neuroimaging.
Traps
- Assuming all disc swelling is papilloedema (it can be optic neuritis, AION, etc.).
- Forgetting that a relative afferent pupillary defect indicates optic nerve disease.
- Missing that CN III palsy with a dilated pupil suggests compression (e.g., aneurysm).
- Confusing comitant (non-paralytic) with incomitant (paralytic) strabismus.
Rule of thumb
Painful visual loss with an RAPD = optic neuritis; painless disc swelling with headache = papilloedema.
Worked example
A patient has sudden vertical diplopia and tilts the head to the opposite shoulder. Diagnose CN IV palsy; perform cover test and consider neuroimaging if new.