Erratum

(To those students who attended my bedside teaching yesterday, when we saw a woman with visual problem.)

Please accept my apology for giving some mistaken remarks on Marcus-Gunn pupil.

In short, the Marcus Gunn phenomenon (relative afferent pupillary defect) refers to the observation that the patient's pupils appear to dilate when a torch is swung from the normal eye to the diseased one. In traditional case, the affected eye still senses the light and produces pupillary sphincter constriction but is delayed, typically due to a slower conduction as a result of optic nerve demyelination.

It should be observed at the diseased eye - although the same happening could be found in the other eye (as stated in our discussion yesterday), but is more difficult to be seen.

PS. I try not to talk about medicine here, but I find no better place to show this correct piece of information to my students (since I do not know there whereabouts), and it is important to say I am sorry.