Monitoring vigilance during perimetry by using pupillography

PURPOSE. To report and present data on a method for monitoring patient vigilance during a visual field test by using pupillometry. METHODS. Pupil diameter was recorded at 60 Hz with an eye movement tracking system in 13 patients attending the glaucoma outpatient clinics at Manchester Royal Eye Hospital. The patients were instructed to fixate a central target and to press a response button when they saw a stimulus that was randomly presented 5 degrees to the left or right of fixation. A repetitive up/down bracketing strategy was used (1-dB steps, 2-second interstimulus intervals, 10-minute duration) at these two locations. Wavelet analysis was used to extract a denoised measure of the pupil diameter and the amplitude of any pupillary fatigue waves. The relationship between the probability of seeing a stimulus and these two components of the pupil response was investigated. RESULTS. Good pupil data were obtained from 12 patients. Most (8/12) showed gradual miosis and periods of pupillary fatigue waves during the recording session. Pupillary fatigue waves became more evident with test duration, and the probability of seeing a stimulus was higher when the pupil was dilated (P < 0.001) and the amplitude of the papillary fatigue waves was low (P < 0.001). CONCLUSIONS. Pupil miosis and fatigue wave amplitude are related to vigilance in patients who take a perimetric-type test. Pupillography can be used to investigate vigilance and how it contributes to perimetric variability.