From WikiProjectMed
Jump to navigation Jump to search
A large difference in the size of the pupils following application of Tropicamide in the right eye only.

Anisocoria is a condition characterized by an unequal size of the eyes' pupils. Affecting up to 20% of the population, anisocoria is often entirely harmless, but can be a sign of more serious medical problems.

Signs and symptoms

The clinical presentation may include the following in an affected individual:[2]

  • Fever
  • Headache
  • Ptosis
  • Eye pain


Anisocoria is a common condition, defined by a difference of 0.4 mm or more between the sizes of the pupils of the eyes.[3]

Anisocoria has various causes:[4]


Causes of anisocoria range from benign (normal) to life-threatening conditions. Clinically, it is important to establish whether anisocoria is more apparent in dim or bright light to clarify if the larger pupil or smaller pupil is the abnormal one.

  • Anisocoria which is worsened (greater asymmetry between the pupils) in the dark suggests the small pupil (which should dilate in dark conditions) is the abnormal pupil and suggests Horner's syndrome or mechanical anisocoria. In Horner's syndrome sympathetic nerve fibers have a defect, therefore the pupil of the involved eye will not dilate in darkness. If the smaller pupil dilates in response to instillation of apraclonidine eye drops, this suggests Horner's syndrome is present.
  • Anisocoria which is greater in bright light suggests the larger pupil (which should constrict in bright conditions) is the abnormal pupil. This may suggest Adie tonic pupil, pharmacologic dilation, oculomotor nerve palsy, or damaged iris.

A relative afferent pupillary defect (RAPD) also known as a Marcus Gunn pupil does not cause anisocoria.

Some of the causes of anisocoria are life-threatening, including Horner's syndrome (which may be due to carotid artery dissection) and oculomotor nerve palsy (due to a brain aneurysm, uncal herniation, or head trauma).

If the examiner is unsure whether the abnormal pupil is the constricted or dilated one, and if a one-sided drooping of the eyelid is present then the abnormally sized pupil can be presumed to be the one on the side of the ptosis. This is because Horner's syndrome and oculomotor nerve lesions both cause ptosis.

Anisocoria is usually a benign finding, unaccompanied by other symptoms (physiological anisocoria). Old face photographs of patients often help to diagnose and establish the type of anisocoria.

It should be considered an emergency if a patient develops acute onset anisocoria. These cases may be due to brain mass lesions which cause oculomotor nerve palsy. Anisocoria in the presence of confusion, decreased mental status, severe headache, or other neurological symptoms can forewarn a neurosurgical emergency. This is because a hemorrhage, tumor or another intracranial mass can enlarge to a size where the third cranial nerve (CN III) is compressed, which results in uninhibited dilatation of the pupil on the same side as the lesion.[9]


In terms of management the problem which is related to the anisocoria will need to be treated (anisocoria needs no treatment).[2]

Popular culture

  • English singer David Bowie exhibited anisocoria, owing to a teenage injury.[10]
  • In the season 10 Big Bang Theory Comic-Con special, Steve Molaro told a story about how he first met actor Judd Hirsch and was taken aback by his dilated pupil. One of the other writers researched it and discovered that Judd Hirsch has anisocoria.
  • American actress Melissa Benoist developed this condition in 2015.
  • American artist Ze Frank has the condition. He was listed as second author on a paper published in The Journal of Neuroscience,[11] which was featured briefly in episode 21 of the show named a show on May 25, 2012 called My Pupils, explaining that his study of neuroscience of vision was motivated by his harmless anisocoria condition.[12][13]


Anisocoria is composed of prefix, root and suffix:

  • prefix: aniso- from the Greek language (meaning: unequal), which in turn comes from an: meaning not and iso: meaning equal
  • the root word: cor, from the Greek word "korē" meaning: pupil of the eye
  • -ia, which is a Latin suffix meaning: disease; pathological or abnormal condition

Thus, anisocoria means the condition of unequal pupil(s).

See also


  1. "anisocoria". Unabridged. Random House.
  2. 2.0 2.1 "What Is Anisocoria?". American Academy of Ophthalmology. 18 April 2022. Archived from the original on 3 March 2022. Retrieved 5 September 2022.
  3. Lam, BL; Thompson, HS; Corbett, JJ (Jul 15, 1987). "The prevalence of simple anisocoria". American Journal of Ophthalmology. 104 (1): 69–73. doi:10.1016/0002-9394(87)90296-0. PMID 3605282.
  4. John P.Whitcher; Paul Riordan-Eva (2007-10-18). Vaughan & Asbury's general ophthalmology (17th ed.). McGraw-Hill Medical. p. 293. ISBN 978-0071443142.
  5. London, Richard; Richrer Erringer, Ellen; Wyafr, Harry J. (March 1991). "Variation and Clinical Observation With Different Conditions of Illumination and Accommodation". Investigative Ophthalmology & Visual Science. 32 (3): 501–9.
  6. Anisocoria Archived 2022-08-30 at the Wayback Machine. Medscape Reference. Accessed April 15, 2012.
  7. . It is also seen in some people who consume diphenydramine (brand name "Benadryl") for an extended period of time, or if an astringent eye drop like Visine is used in one eye and not the other, often in concurrence with the presence of contact lenses.van der Donck, I.; Mulliez, E.; Blanckaert, J. (2004), "Angel's Trumpet (Brugmansia arborea) and mydriasis in a child - A case report", Bulletin de la Société Belge d'Ophtalmologie, 292: 53–56, ISSN 0081-0746, archived from the original on 2009-05-05, retrieved 2022-08-31
  8. "Anisocoria Differential Diagnoses". Archived from the original on 26 May 2017. Retrieved 3 June 2017.
  9. Medscape, online. "Anisocoria Clinical Presentation". Archived from the original on 9 September 2017. Retrieved 25 November 2012.
  10. Hunt, Kevin (January 11, 2016). "The remarkable story behind David Bowie's most iconic feature". The Conversation. Archived from the original on November 1, 2020. Retrieved January 17, 2016.
  11. Rozas C, Frank H, Heynen AJ, Morales B, Bear MF, Kirkwood A (2001). "Developmental inhibitory gate controls the relay of activity to the superficial layers of the visual cortex". J Neurosci. 21 (17): 6791–6801. doi:10.1523/JNEUROSCI.21-17-06791.2001. PMC 6763109. PMID 11517267.
  12. My Pupils Archived 2013-05-01 at the Wayback Machine, episode 21 of a show
  13. "My Pupils". YouTube. March 25, 2012. Archived from the original on 2021-12-21.

Further reading

  • "Anisocoria." "Stedman's Medical Dictionary, 27th ed." (2000). ISBN 0-683-40007-X
  • Victor, Maurice and Allan H. Ropper. "Adams and Victor's Principles of Neurology, 7th ed." (2001). ISBN 0-07-067497-3

External links

External resources