Physical Exam

Pupillary Light Reaction

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Video coming September 2026

How to Perform

In dim lighting, ask the patient to fixate on a distant target or your nose. Shine a bright light into one eye and watch that pupil constrict (direct response) while the opposite pupil constricts at the same time (consensual response); repeat for the other eye.

How to Interpret

Poor Neurologic Outcome

Absent pupillary light reflex in a comatose patient after cardiac arrest

Rule in

HelpfulNo CI

Rule out

Minimally helpfulNo CI

Evidence:Strong

Serious Eye Disease

Photophobia on indirect (consensual) illumination in a patient with a red eye

Rule in

Very helpful

Rule out

Minimally helpful

Evidence:Limited

Photophobia on direct illumination in a patient with a red eye

Rule in

Helpful

Rule out

Somewhat helpful

Evidence:Limited

Structural Brain Lesion

Anisocoria greater than 1 mm in a patient with impaired consciousness

Rule in

HelpfulDerived CI

Rule out

Minimally helpfulDerived CI

Evidence:Limited

Absent light reflex in at least one eye in a patient with impaired consciousness

Rule in

Somewhat helpfulDerived CI

Rule out

—

Evidence:LimitedResearch in progress

References

Research in progress on one or more findings above; ratings may change.

Cox TA, Thompson HS, Corbett JJ. Relative afferent pupillary defects in optic neuritis. Am J Ophthalmol. 1981;92(5):685-690. PMID: 7304695.
Hoffman JR, Schriger DL, Luo JS. The empiric use of naloxone in patients with altered mental status: a reappraisal. Ann Emerg Med. 1991;20(3):246-252. PMID: 1996818.
Brennan PM, Murray GD, Teasdale GM. Simplifying the use of prognostic information in traumatic brain injury. Part 1: The GCS-Pupils score: an extended index of clinical severity. J Neurosurg. 2018;128(6):1612-1620. PMID 29631516. DOI 10.3171/2017.12.JNS172780
Wang CH, Wu CY, Liu CC, Hsu TC, Liu MA, Wu MC, Tsai MS, Chang WT, Huang CH, Lee CC, Chen SC, Chen WJ. Neuroprognostic Accuracy of Quantitative Versus Standard Pupillary Light Reflex for Adult Postcardiac Arrest Patients: A Systematic Review and Meta-Analysis. Crit Care Med. 2021;49(10):1790-1799. PMID 34259437. DOI 10.1097/CCM.0000000000005045
Scotter J, Hendrickson S, Marcus HJ, Wilson MH. Prognosis of patients with bilateral fixed dilated pupils secondary to traumatic extradural or subdural haematoma who undergo surgery: a systematic review and meta-analysis. Emerg Med J. 2015;32(8):654-659. PMID: 25385844.
Narayana S, McGee S. Bedside diagnosis of the 'red eye': a systematic review. Am J Med. 2015;128(11):1220-1224.e1. doi:10.1016/j.amjmed.2015.06.026. PMID: 26169885.
Narayana S, McGee S. Bedside diagnosis of the 'red eye': a systematic review. Am J Med. 2015;128(11):1220-1224.e1. PMID: 26169885.
Tokuda Y, Nakazato N, Stein GH. Pupillary evaluation for differential diagnosis of coma. Postgrad Med J. 2003;79(927):49-51. PMID: 12566553.
Harrison MJG. Clinical distinction of cerebral haemorrhage and cerebral infarction. Postgrad Med J. 1980;56:629-632. PMID: 7465470.
Fujiwara S, Fujii K, Nishio S, Matsushima T, Fukui M. Oculomotor nerve palsy in patients with cerebral aneurysms. Neurosurg Rev. 1989;12(2):123-132. PMID: 2779790.
Yoo YJ, Hwang JM, Yang HK. Dilute pilocarpine test for diagnosis of Adie's tonic pupil. Sci Rep. 2021;11(1):10089. PMID: 33980910.
Bickley LS, Szilagyi PG, Hoffman RM, Soriano RP. Bates' Guide to Physical Examination and History Taking. 13th ed. Philadelphia, PA: Wolters Kluwer; 2021.
Swartz MH. Textbook of Physical Diagnosis: History and Examination. 9th ed. Philadelphia, PA: Elsevier; 2025.

Research last updated September 9, 2026.