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PronunciationAnisocoria_header_cell_0_1_0 Anisocoria_cell_0_1_1
SpecialtyAnisocoria_header_cell_0_2_0 Ophthalmology Q521953?uselang=en#P1995Anisocoria_cell_0_2_1

Anisocoria is a condition characterized by an unequal size of the eyes' pupils. Anisocoria_sentence_0

Affecting up to 20% of the population, anisocoria is often entirely harmless, but can be a sign of more serious medical problems. Anisocoria_sentence_1

Causes Anisocoria_section_0

Anisocoria is a common condition, defined by a difference of 0.4 mm or more between the sizes of the pupils of the eyes. Anisocoria_sentence_2

Anisocoria has various causes: Anisocoria_sentence_3


Diagnosis Anisocoria_section_1

Causes of anisocoria range from benign (normal) to life-threatening conditions. Anisocoria_sentence_4

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_sentence_5


  • 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_item_1_7
  • 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.Anisocoria_item_1_8

A relative afferent pupillary defect (RAPD) also known as a Marcus Gunn pupil does not cause anisocoria. Anisocoria_sentence_6

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). Anisocoria_sentence_7

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. Anisocoria_sentence_8

This is because Horner's syndrome and oculomotor nerve lesions both cause ptosis. Anisocoria_sentence_9

Anisocoria is usually a benign finding, unaccompanied by other symptoms (physiological anisocoria). Anisocoria_sentence_10

Old face photographs of patients often help to diagnose and establish the type of anisocoria. Anisocoria_sentence_11

It should be considered an emergency if a patient develops acute onset anisocoria. Anisocoria_sentence_12

These cases may be due to brain mass lesions which cause oculomotor nerve palsy. Anisocoria_sentence_13

Anisocoria in the presence of confusion, decreased mental status, severe headache, or other neurological symptoms can forewarn a neurosurgical emergency. Anisocoria_sentence_14

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. Anisocoria_sentence_15

Popular culture Anisocoria_section_2


  • English singer David Bowie exhibited anisocoria, owing to a teenage injury.Anisocoria_item_2_9
  • 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.Anisocoria_item_2_10
  • American actress Melissa Benoist developed this condition in 2015.Anisocoria_item_2_11

Etymology Anisocoria_section_3

Anisocoria is composed of prefix, root and suffix: Anisocoria_sentence_16


  • prefix: aniso- from the Greek language (meaning: unequal), which in turn comes from an: meaning not and iso: meaning equalAnisocoria_item_3_12
  • the root word: cor, from the Greek word "korē" meaning: pupil of the eyeAnisocoria_item_3_13
  • -ia, which is a Latin suffix meaning: disease; pathological or abnormal conditionAnisocoria_item_3_14

Thus, anisocoria means the condition of unequal pupil(s). Anisocoria_sentence_17

See also Anisocoria_section_4


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