Monocular versus binocular pupillometry

Purpose: To quantify differences between monocular and binocular pupil size measurement under scotopic and mesopic conditions. Setting: Department of Ophthalmology, Johannes Gutenberg-University, and Department of Medical Biometry, Epidemiology and Informatics, University of Mainz, Mainz, Germany. Methods: Computerized dynamic pupillometry (P2000 SA, Procyon Instruments Ltd.) was used at 3 illumination levels: scotopic at 0.03 lux, mesopic low at 0.82 lux, and mesopic high at 6.4 lux. One hundred forty eyes of 70 healthy volunteers without ocular pathology were examined. The subjects were divided into 2 groups. In the first group, the pupil diameter was measured binocularly first. In the second group, monocular measurement was performed first. For statistical analysis, data description was based on medians and quartiles of the respective pupil diameter measurements. Intraindividual significance was based on sign tests, and interindividual comparison were based on 2-sample Wilcoxon tests. Results: In all eyes, statistically significant differences were found in pupil size, with higher values for the monocular measurement under low and high mesopic conditions (P = .000). For scotopic conditions, a trend toward higher values in monocular measurement was observed that approached statistical significance. Conclusions: Results indicate that binocular measurement may imitate the patient's life conditions more realistically. Therefore, in eyes with a large pupil diameter with the risk for postoperative scotopic phenomena, binocular measurement should be considered before refractive surgery.