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Anisocoria
Classification and external resources

Anisocoria
ICD-10 H57.0
ICD-9 379.41
OMIM 106240
DiseasesDB 724
eMedicine emerg/29 neuro/479 oph/160
MeSH D015875

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

Contents

Causes

In the absence of any deformities of the iris or eyeball proper, anisocoria is usually the result of a defect in efferent nervous pathways controlling the pupil traveling in the oculomotor nerve (parasympathetic fibers) or the sympathetic pathways. Physical lesions and drugs causing anisocoria will do so via disruption of these pathways.

May be associated with adie syndrome.

Some examples of drugs which may affect the pupils include pilocarpine, cocaine, tropicamide, MDMA and scopolamine. Such alkaloids present in plants of the genus Brugmansia may also induce anisocoria.[1]

Additionally, dilation of the pupil is termed mydriasis and constriction of the pupil is termed miosis.

Interpretation

Clinically, it is important to establish which of the two pupils is behaving abnormally.

  • If the smaller of the two pupils is the abnormal one, dimming the ambient light will not cause it to dilate, in which case a defect in sympathetic fibers is suspected, as seen in Horner's syndrome.
  • Alternatively, if the abnormal pupil is the larger one, it will fail to contract in response to light, raising suspicion for a parasympathetic nerve defect, possibly an oculomotor nerve palsy.

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

When anisocoria occurs and the examiner is unsure whether the abnormal pupil is the constricted or dilated one, if a one-sided ptosis is present then the abnormally sized pupil can be presumed to be the one on the side of the ptosis, as a Horner's syndrome [sympathetic lesion], and an Occulomotor nerve lesion both cause ptosis.

Anisocoria in the presence of confusion, decreased mental status, severe headache, etc. can be a sign of blood, tumour or other pathology inside the brain pressing down on some critical nerves. This is a neurosurgical emergency requiring emergency treatment and possibly surgery.

See also

References

  1. ^ 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 Societe Belge d'Ophtalmologie 292: 53–56, ISSN 0081-0746, http://www.ophthalmologia.be/download.php?dof_id=223  
  • "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

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