Marcus Gunn Pupil


Marcus Gunn Pupil: (AKA relative afferent pupillary defect or RAPD) A pupil that responds by constricting more to an indirect than to a direct light, seen with unilateral optic nerve or retinal disease,


1902 First description by Robert Marcus Gunn

It is not sufficient to find that it (the pupil) contracts well or fairly well on exposure; the eye must also be kept under direct stimulation of light and the pupil watched as to whether or not it shows that secondary dilatation under continued exposure that is found associated with the amblyopia of retro-ocular neuritis. If the vision of one eye only is affected, it is important to compare the behaviour of the two pupils when stimulated directly or consensually. Thus, in partial affection of the right optic nerve the right pupil will show this secondary dilatation during continued exposure to direct stimulation, while the left pupil will show the same behaviour on consensual stimulation. On the other hand, on stimulation of the left eye both the right and left pupil will behave normally. I need not remind you of the importance of this observation, inasmuch as it not infrequently enables us to diagnose a retro-ocular neuritis in the absence of all ophthalmoscopic evidence.

R Marcus Gunn 1902:21:275
Associated Persons
Alternative names
  • Gunn’s pupillary phenomenon
  • Marcus Gunn pupillary phenomenon
  • Relative afferent pupillary defect (RAPD)

eponymictionary CTA 2


medical etymology

BA MA (Oxon) MBChB (Edin) FACEM FFSEM. Emergency physician, Sir Charles Gairdner Hospital.  Passion for rugby; medical history; medical education; and asynchronous learning #FOAMed evangelist. Co-founder and CTO of Life in the Fast lane | Eponyms | Books | Twitter |

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