Purpose: To compare four scotopic pupil measuring techniques to determine whether a statistically significant difference exists among the techniques for each observer or between the observers for each technique.
Methods: Cross-sectional study performed on 200 eyes of 100 healthy individuals. Two observers performed pupillometry four times per pupil using the Rosenbaum card with red light, Rosenbaum card with blue light, Iowa pupillometer, and Colvard pupillometer. All measurements were recorded in scotopic conditions with each examiner masked to the other's results.
Results: Both examiners measured mean pupil diameters > 6.0 mm for all modalities except the Colvard device whose mean measurements were the smallest. The Iowa pupillometer and Rosenbaum card with red light produced the largest pupil measurements and were the most similar for both observers. The mean pupil diameter obtained by observer 1 was smaller compared with observer 2 while using the Rosenbaum card with blue light, but this was not significant (P = .2574). The mean pupil diameter obtained by observer 1 was larger compared with observer 2 while using the Colvard pupillometer and this was statistically different after adjusting for eye color (P = .0370). The mean pupil diameters of blue irides and brown irides are significantly higher than the measurements obtained for hazel irides (P = .0271 and P = .0445, respectively).
Conclusions: Due to the complex interaction among observer, pupillometry technique, and iris color, one cannot compare the four techniques to each other with the same observer, nor can one compare the two observers irrespective of the technique.