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Marcus Gunn pupil (afferent pupillary defect)

Afferent pupillary defect. Etiology: 1) iridocyclitis - corneal or lens opacity; light does not reach retina 2) extensive retinal lesion; retinal degeneration 3) optic nerve lesion* - optic nerve degeneration - optic neuritis - multiple sclerosis - ischemic optic neuropathy [8] - optic atrophy - brain tumor - optic nerve meningioma - optic nerve glioma - angle-closure glaucoma * afferent pupillary response uses subcortical pathway, thus occipital lobe lesion not an etiology Physical examination: - detected during the swinging-flashlight test* - normal response is equal constriction of both pupils, regardless of which eye the light is directed at - this indicates an intact direct & consensual pupillary light reflex - light directed in the affected eye will cause only mild constriction of both pupils* - light in the unaffected eye will cause a normal constriction of both pupils * paradoxical dilation of the pupils when the swinging light is shifted from the unaffected eye to the affected eye [3] Clinical manifestations: - failure of pupil to constrict appropriately with increasing light Special laboratory: - ophthalmoscopy may show optic nerve pallor Radiology: - MRI neuroimaging brain & orbits [8] Differential diagnosis: - defect in parasympathetic fibers that innervate sphincter pupillae* * degeneration of afferent of efferent midbrain synapses may yield a similar picture

Related

pupil (P)

General

eye disease (ophthalmopathy) sign/symptom

References

  1. Stedman's Medical Dictionary 27th ed, Williams & Wilkins, Baltimore, 1999
  2. Ferri's Clinical Advisor, Instant Diagnosis and Treatment, Ferri FF (ed), Mosby, Philadelphia, 2003, pg 1215
  3. Medical Knowledge Self Assessment Program (MKSAP) 11, American College of Physicians, Philadelphia 1998 - Medical Knowledge Self Assessment Program (MKSAP) 19 Board Basics. An Enhancement to MKSAP19. American College of Physicians, Philadelphia 2022
  4. Wikipedia: Marcus Gunn pupil http://en.wikipedia.org/wiki/Marcus_Gunn_pupil
  5. Ichhpujani P, Rome JE, Jindal A et al Comparative study of 3 techniques to detect a relative afferent pupillary defect. J Glaucoma. 2011 Dec;20(9):535-9. PMID: 20852433
  6. Volpe NJ, Dadvand L, Kim SK et al Computerized binocular pupillography of the swinging flashlight test detects afferent pupillary defects. Curr Eye Res. 2009 Jul;34(7):606-13. PMID: 19899974
  7. Younis AA, Eggenberger ER. Correlation of relative afferent pupillary defect and retinal nerve fiber layer loss in unilateral or asymmetric demyelinating optic neuropathy. Invest Ophthalmol Vis Sci. 2010 Aug;51(8):4013-6 PMID: 20207978
  8. Geriatric Review Syllabus, 8th edition (GRS8) Durso SC and Sullivan GN (eds) American Geriatrics Society, 2013
  9. Lee AG, Chau FY, Golnik KC, Kardon RH, Wall M The diagnostic yield of the evaluation for isolated unexplained optic atrophy. Ophthalmology 2005 May 10; 112:757 PMID: 15878053
  10. Lawlor M, Quartilho A, Bunce C et al. Patients with normal tension glaucoma have relative sparing of the relative afferent pupillary defect compared to those with open angle glaucoma and elevated intraocular pressure. Invest Ophthalmol Vis Sci. 2017;58(12):5237-5241 PMID: 29049724 Free article https://iovs.arvojournals.org/article.aspx?articleid=2657596
  11. Schmidt F, Connolly F, Maas MB et al. Objective assessment of a relative afferent pupillary defect by B-mode ultrasound. PLoS One. 2018;13(8):e0202774 PMID: 30148895 PMCID: PMC6110480 Free PMC article https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0202774