Neuro-ophthalmology
Core concepts
Master the afferent vs. efferent pathway and the pupil light reflex. Know optic neuritis (painful, unilateral, relative afferent pupillary defect, MS association), papilledema (bilateral, raised ICP, preserved acuity until late), and ischemic optic neuropathy (NAION vs. giant cell arteritis). Understand cranial nerve palsies (III, IV, VI) and the cavernous sinus syndrome. Know Horner syndrome (ptosis, miosis, anhidrosis) and the localization (first-order central, second-order preganglionic, third-order postganglionic).
Traps
A key trap is NAION vs. optic neuritis - NAION is painless, older patient, altitudinal defect, and disc edema; optic neuritis is painful with movement, younger, and has RAPD. Another trap is giant cell arteritis - suspect in any older patient with sudden vision loss and jaw claudication; treat with high-dose steroids immediately. Also know pupil-sparing third nerve palsy can be ischemic (diabetic) vs. compressive (aneurysm).
Worked example
A 70-year-old with sudden painless vision loss, altitudinal field defect, and a swollen optic disc. Rule of thumb: painless altitudinal loss in an older patient = NAION, but always rule out GCA with ESR/CRP and ask about jaw claudication; if GCA is suspected, start steroids before biopsy.