Encyclopedia of Clinical Neuropsychology

2018 Edition
| Editors: Jeffrey S. Kreutzer, John DeLuca, Bruce Caplan

Pupillary Light Response, Pupillary Response

  • Samantha BackhausEmail author
Reference work entry
DOI: https://doi.org/10.1007/978-3-319-57111-9_272


Pupillary light response (PLR) is the reduction of pupil size in response to direct light. This is the most common stimulus for pupillary constriction. Reflex pupillary constriction is also involved in convergence and accommodation for nearby objects. It is often used to determine which cranial nerves are damaged in an injury. PLR is typically measured as direct and consensual responses, which are graded as PERRLA (pupils equal round reactive to light and accommodation) if they are normal. A direct pupillary reflex means that the pupil quickly constricts briskly when the light is shone in that eye. This can be graded as 1, 2, 3, or 4. Consensual pupillary reflex means the pupil constricts when light is shone in the opposite eye, a normal response.

Current Knowledge

Under normal circumstances, pupils typically constrict equally. A lack of pupillary reflex can be caused by optic nerve damage, oculomotor nerve damage, brain death, and central nervous system depressants (e.g.,...

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References and Readings

  1. Adams, R. D., Victor, M., & Ropper, A. H. (1997). Craniocerebral trauma. In R. D. Adams, M. Victor, & A. H. Ropper (Eds.), Principles of neurology (6th ed., pp. 875–901). New York: McGraw-Hill.Google Scholar

Copyright information

© Springer International Publishing AG, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Department of NeuropsychologyRehabilitation Hospital of IndianaIndianapolisUSA