PUPILLOMETRIC ANALYSIS OF THE ABSENT LIGHT REFLEX

Objective: To measure che ''absent light reflex'' with an infrared pup illometer. Setting: Intensive care unit of the Moffitt-Long Hospitals at the University of California-San Francisco. Subjects: Three patient s lacking a pupillary light reflex early in the postresuscitation peri od and a consecutive sample of comatose patients in the intensive care unit in whom clinical (penlight) examination demonstrated an absent l ight reflex. Interventions: A portable infrared pupillometer was moved to the bedside of patients thought to have an absent light reflex, an d 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 postresu scitation patients whose pupillary light reflex was thought to be clin ically absent but found to be present, although small, with infrared p upillometry. All patients in the intensive care unit with known brain death had an absent light reflex, whereas four of nine of those withou t brain death but with dilated nonreactive pupils had a small light re flex detectable by the infrared pupillometer. This reflex was characte rized by a low maximum constriction velocity and low amplitude of cons triction. Conclusion: Infrared pupillometry can sometimes reveal the p resence of midbrain function that might otherwise be missed in paralyz ed patients.