Marcus Gunn pupil

Marcus Gunn pupil
Classification and external resources
The left optic nerve and the optic tracts. A Marcus Gunn pupil indicates an afferent defect, usually at the level of the retina or optic nerve. Moving a bright light from the unaffected eye to the affected eye would cause both eyes to dilate, because the ability to perceive the bright light is diminished.
DiseasesDB	29599

For the jaw-winking syndrome, see Marcus Gunn phenomenon.

Marcus Gunn pupil (relative afferent pupillary defect) is a medical sign observed during the swinging-flashlight test^[1] whereupon the patient's pupils constrict less (therefore appearing to dilate) when a bright light is swung from the unaffected eye to the affected eye. The affected eye still senses the light and produces pupillary sphincter constriction to some degree, albeit reduced.

The most common cause of Marcus Gunn pupil is a lesion of the optic nerve (proximal to the optic chiasm) or severe retinal disease. It is named after Scottish ophthalmologist Robert Marcus Gunn.^[2]

Examination

The Marcus Gunn pupil is a relative afferent pupillary defect indicating a decreased pupillary response to light in the affected eye.^[3]

In the swinging flashlight test, a light is alternately shone into the left and right eyes. A normal response would be equal constriction of both pupils, regardless of which eye the light is directed at. This indicates an intact direct and consensual pupillary light reflex. When the test is performed in an eye with an afferent pupillary defect, light directed in the affected eye will cause only mild constriction of both pupils (due to decreased response to light from the afferent defect), while light in the unaffected eye will cause a normal constriction of both pupils (due to an intact afferent path, and an intact consensual pupillary reflex). Thus, light shone in the affected eye will produce less pupillary constriction than light shone in the unaffected eye.

A Marcus Gunn Pupil is distinguished from a total CN II lesion, in which the affected eye perceives no light. In that case, shining the light in the affected eye produces no effect.

Anisocoria is absent. A Marcus Gunn pupil is seen, among other conditions, in optic neuritis. It is also common in retrobulbar optic neuritis due to multiple sclerosis but only for 3-4 weeks, until the visual acuity begins to improve in 1–2weeks and may return to normal. ^[4]

See also

• Adie syndrome
• Anisocoria
• Cycloplegia
• Miosis
• Parinaud's syndrome
• Syphilis

References

1. ^ "utah.edu". http://umed.med.utah.edu/neuronet/lectures/2002/Basics%20in%20Neuro-Ophthalmology.htm. Retrieved 2009-05-27. 
2. ^ doctor/2687 at Who Named It?
3. ^ Pearce J (November 1996). "The Marcus Gunn pupil". J. Neurol. Neurosurg. Psychiatr. 61 (5): 520. doi:10.1136/jnnp.61.5.520. PMC 1074053. PMID 8937350. http://jnnp.bmj.com/cgi/pmidlookup?view=long&pmid=8937350. 
4. ^ Mumenthaler Neurology 4ed, Thieme 2004, page 486 Demyelinating diseases

External links

• 1611005962 at GPnotebook

Lens

Cataract · Aphakia · Ectopia lentis

Retina

Retinitis (Chorioretinitis, Cytomegalovirus retinitis) · Retinal detachment · Retinoschisis · Ocular ischemic syndrome/Central retinal vein occlusion · Retinopathy (Bietti's crystalline dystrophy, Coats disease, Diabetic retinopathy, Hypertensive retinopathy, Retinopathy of prematurity) · Macular degeneration · Retinitis pigmentosa · Retinal haemorrhage · Central serous retinopathy · Macular edema · Epiretinal membrane · Macular pucker · Vitelliform macular dystrophy · Leber's congenital amaurosis · Birdshot chorioretinopathy

Other

Glaucoma/Ocular hypertension · Floater · Leber's hereditary optic neuropathy · Red eye · Keratomycosis · Phthisis bulbi

Pathways

Optic nerve and optic disc	Optic neuritis · Papilledema (Foster Kennedy syndrome) · Optic atrophy/Optic neuropathy (Leber's hereditary optic neuropathy, Kjer's optic neuropathy) · Optic disc drusen · Toxic and nutritional optic neuropathy · Ischemic optic neuropathy (AION, PION)
Ocular muscles, binocular movement, accommodation	Paralytic strabismus Ophthalmoparesis · Progressive external ophthalmoplegia · Palsy (III, IV, VI) · Kearns-Sayre syndrome Other strabismus Esotropia/Exotropia · Hypertropia · Heterophoria (Esophoria, Exophoria) · Brown's syndrome · Duane syndrome Other binocular Conjugate gaze palsy · Convergence insufficiency · Internuclear ophthalmoplegia · One and a half syndrome
Refraction	Refractive error: Hyperopia/Myopia · Astigmatism · Anisometropia/Aniseikonia · Presbyopia
Visual disturbances and blindness	Amblyopia · Leber's congenital amaurosis · Subjective (Asthenopia, Hemeralopia, Photophobia, Scintillating scotoma) · Diplopia · Scotoma · Anopsia (Binasal hemianopsia, Bitemporal hemianopsia, Homonymous hemianopsia, Quadrantanopia) · Color blindness (Achromatopsia, Dichromacy, Monochromacy) · Nyctalopia (Oguchi disease) · Blindness/Low vision
Pupil	Anisocoria · Argyll Robertson pupil · Marcus Gunn pupil · Adie syndrome · Miosis · Mydriasis · Cycloplegia · Parinaud's syndrome
Other	Nystagmus

Eye infections

Trachoma · Onchocerciasis

M: EYE anat(g/a/p)/phys/devp/prot noco/cong/tumr, epon proc, drug(S1A/1E/1F/1L)