Repeatability of Pupil Size Measurements in Refractive Surgery Candidates

Abstract

Purpose: : To assess the individual variety of of the dark-adapted pupil diameter in refractive surgery candidates with a digital infrared pupillometer over 2 testing sessions.

Methods: : Retrospective study of 292 eyes of 146 consecutive refractive surgery candidates (mean age 36.3 years ± 10.2 [SD]). Pupil size was measured at three different illumination levels (scotopic at 0.03 lux, mesopic low at 0.82 lux, and mesopic high at 6.4 lux) with a digital infrared pupillometer (Procyon P2000 SA pupillometer, Procyon Instruments Ltd.). Prior to measurement a 5 minute standardized dark-adaptation protocol was followed. Mean time between both mesurements was 53 days ± 62.8 [SD].

Results: : The difference of 2 consecutive measurements was statistically significant under low mesopic conditions (p<0.01) and high mesopic conditions (p<0.01), but not under scotopic conditions (p=0.362). A considerable difference (>0.5 mm) between both testing sessions was found in 19% of all measurements under scotopic conditions, 41% under low mesopic and 37% under high mesopic conditions.

Conclusions: : Pupil size under low illumination levels might be underestimated if the pupil diameter is only assessed once in refractive surgery candidates.

Keywords: refractive surgery • refractive surgery: LASIK • refractive surgery: PRK