Automated pupil size determination for evaluating fluctuations in physiological arousal

Measurement of pupil diameter and the rate of pupil diameter fluctuation have been found to be a possible determinant of measures of physiological vigilance. This paper reviews an initial study of an imaging method for pupillometric analysis. The pupil parameter determination is based on a dynamic threshold approach, which accurately segments the pupil from the retina. A video camera is used to capture the pupil while the patient is attending to a vigilance task. The accuracy of pupil radii and area measurements were found to be of the order of 5%. Examples of several images and results are given in the paper. The pupillometric imaging technique will subsequently be extended to evaluate its sensitivity to measures of fluctuating arousal amongst normal sleepy individuals and subjects suffering from a sleep disorder, narcolepsy