Repeated pupil size measurements in refractive surgery candidates

Purpose: To evaluate the individual variation in pupil diameter measurements in refractive surgery candidates under standardized conditions over 2 testing sessions using a digital infrared pupillometer. Setting: Department of Ophthalmology, University Medical Center Regensburg, Regensburg, Germany. Methods: The pupil size in both eyes of consecutive refractive surgery candidates was measured under 2 illumination levels (scotopic at 0.03 lux, low mesopic at 0.82 lux) with a digital infrared pupillometer (Procyon P2000 SA). Before measurement, a standardized dark-adaptation protocol was used. Measurements were taken twice on separate occasions. Results: The study evaluated 318 eyes of 159 patients with a mean age of 36.3 years ± 10.2 (SD). The mean interval between measurements was 53 ± 62.8 days. Despite sufficient power (β < 0.05), there was no statistically significant difference between 2 consecutive measurements under scotopic and low mesopic illumination. Conclusion: Using a standardized dark-adaptation protocol, refractive surgery candidates showed no significant variation in scotopic or low mesopic pupil diameter over 2 testing sessions.