1. Answer: C (Optic nerve)
The patient’s history is typical of optic neuritis. Although there are other causes of pain on ocular movement (eg. scleritis), these are not associated with reduced colour vision.
- The other options (chiasm, cortex, radiation & tract) would cause bilateral visual deficits
2. Answer: B (R-sided RAPD)
Pupillary light reflex: When light is shone into one eye, the signal is transmitted down the afferent limb of the reflex (optic nerve) and back along the efferent limb (oculomotor nerve) on both sides. This causes bilateral miosis (pupillary constriction).
- In this patient, if light is shone in the unaffected eye then both pupils will constrict. If light is then shone in the affected R eye, in which the signal is attenuated due to optic nerve inflammation, both pupils will appear to dilate as they are ‘constricting to a lesser extent’.