Neuro-ophthalmology
This domain tests optic nerve disease, pupil abnormalities, cranial nerve palsies, visual field defects, and giant cell arteritis. The exam emphasizes urgent recognition and correct imaging.
Core neuro-ophthalmology
- Optic neuritis: painful unilateral vision loss, reduced color vision, RAPD, and disc swelling; associated with MS. NMO is bilateral and severe with AQP4 antibodies.
- Papilledema: bilateral disc swelling from raised ICP; IIH occurs in young obese women and is treated with weight loss and acetazolamide.
- Pupils: Horner syndrome causes ptosis, miosis, and anhidrosis; Adie pupil is tonic; RAPD indicates optic nerve dysfunction; Argyll Robertson pupils suggest neurosyphilis.
- Cranial nerve palsies: pupil-involving CN III palsy suggests aneurysm until proven; pupil-sparing palsy is often diabetic microvascular. CN VI palsy is a false-localizing sign.
- Visual fields: chiasmal lesion gives bitemporal hemianopia; optic tract gives homonymous defect; occipital lesion gives homonymous hemianopia with macular sparing.
- GCA: age over 50, headache, jaw claudication, elevated ESR/CRP. Give steroids immediately and biopsy within 2 weeks.
Worked example
A 74-year-old has sudden vision loss and jaw claudication. Reasoning: GCA. Give IV methylprednisolone before biopsy; the biopsy can remain positive for up to 2 weeks after steroids.
Traps
Do not wait for biopsy to treat GCA. A pupil-sparing third nerve palsy is usually ischemic but must be followed.