Pupillometric Analysis of the 'Absent Light Reflex'
Merlin D. Larson, MD;
Isobel Muhiudeen, MD, PhD
Arch Neurol. 1995;52(4):369-372.
Abstract
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Objective
To measure the "absent light reflex" with an infrared pupillometer.
Setting
Intensive care unit of the Moffitt-Long Hospitals at the University of California—San Francisco.
Subjects
Three patients lacking a pupillary light reflex early in the postresuscitation period and a consecutive sample of comatose patients in the intensive care unit in whom clinical (penlight) examination demonstrated an absent light reflex.
Interventions
A portable infrared pupillometer was moved to the bedside of patients thought to have an absent light reflex, and a series of individual scans were averaged to detect the presence or absence of a light reflex.
Main Results
The study of patients in the intensive care unit was prompted by the observation of three postresuscitation patients whose pupillary light reflex was thought to be clinically absent but found to be present, although small, with infrared pupillometry. All patients in the intensive care unit with known brain death had an absent light reflex, whereas four of nine of those without brain death but with dilated nonreactive pupils had a small light reflex detectable by the infrared pupillometer. This reflex was characterized by a low maximum constriction velocity and low amplitude of constriction.
Conclusion
Infrared pupillometry can sometimes reveal the presence of midbrain function that might otherwise be missed in paralyzed patients.
Author Affiliations
From the Department of Anesthesia, University of California—San Francisco.
THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES
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Cranston et al.
NEJM 2001;345:616-618.
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