Aurora, CO: Pupil size is not predictive of acute cannabis exposure and should not be relied upon as a determinant of marijuana-induced impairment, according to data published in the journal Clinical Toxicology.
Investigators affiliated with the University of Colorado performed pupillometer assessments on 126 participants. Ninety-five participants were assessed at baseline and then again following ad libitum cannabis inhalation. Thirty-five subjects completed the same assessments but did not use cannabis.
Following cannabis inhalation, subjects “did not exhibit a substantial and consistent difference in static pupil diameter relative to controls,” researchers reported.
As a result, the study’s authors cautioned against relying on ocular measures as evidence of cannabis-induced impairment, stating that the tests lacked the accuracy and specificity necessary to be a valid evidentiary tool.
Drug Recognition Evaluators typically perform a variety of ocular measurements, including assessments of pupil size, on drivers they suspect to be under the influence of cannabis.
Full text of the study, “Pupillary dynamics as a marker of acute. Cannabis inhalation,” appears in Clinical Toxicology.