Comparison of three different technologies for pupil diameter measurement
The pupil diameter plays an important role in the occurrence of photopic phenomena after refractive surgery. Standardized estimation can be performed using a lens system with a built-in millimeter scale (Colvard, Oasis Medical, California). A new computerized technique allows dynamic and binocular measurement of the pupil diameter by use of infrared light (P2000SA, Procyon Instruments, London, UK). An additional approach is a wavefront aberrometer based on the Hartmann-Shack principle (WASCA; Asclepion-Meditec-Zeiss, Jena, Germany). These strategies were compared.
Non-randomized comparative trial.
Participants and methods
The pupil diameter of 56 eyes of 28 probands (18 female, mean age 23 years) was measured under scotopic conditions by three independent examiners with each measurement device. The measurement devices were compared intraindividually by pairwise sign tests. Description was based on the intraindividual differences' medians and quantiles.
Median pupil diameters were 6.67 mm for the scale pupillometer (interquartile range 6.07–6.94 mm), 6.60 mm for the dynamic pupillometer (6.0–7.02 mm), and 6.37 mm for the wavefront-based aberrometer (5.9–6.7 mm). Pairwise comparison revealed statistically significant (P<0.05), although not clinically relevant median deviations. Although no clinically relevant median differences were observed (when based on intraobserver means), deviations for single pupil diameter assessments ranged up to 1 mm.
No clinically relevant median deviations were observed in the underlying repeated measurement scenario. The scale pupillometer showed greater interobserver variation than the objective tests.
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