Scotopic measurement of normal pupils: Colvard versus Video Vision Analyzer infrared pupillometer

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Abstract
Purpose: To prospectively measure the scotopic pupil diameter in a normal population and to compare 2 infrared pupillometers for these measurements. Setting: Johann Wolfgang Goethe-University, Department of Ophthalmology, Frankfurt am Main, Germany. Methods: The Colvard infrared pupillometer was compared to the Video Vision Analyzer (VIVA) infrared pupillometer under scotopic light conditions in 33 participants (aged 19 to 55 years). Reliability was assessed by 2 independent examiners (E1, E2). Statistical analysis was performed using a comparison method by Bland and Altman. Results: Mean pupil diameter was 6.16 mm ± 1.20 (SD) (range 3.20 to 9.00 mm) with all measurements taken under scotopic illumination. The mean scotopic pupil diameter was 6.08 ± 1.16 mm (range 3.2 to 8.4 mm) with the Colvard pupillometer and 6.24 ± 1.28 mm (3.5 to 9.0 mm) with the VIVA pupillometer. The mean differences between the Colvard and VIVA were −0.27 mm (E1) and −0.05 mm (E2). Limits of agreement ranged from 1.4 (Colvard) to 2.4 (VIVA). The coefficients of repeatability ranged from 0.7 (Colvard) to 1.1 (VIVA). Conclusions: A mean scotopic pupil diameter of 6.15 mm with a maximal pupil size of 9.00 mm can be expected in a normal population; this should be considered in refractive corneal and refractive lens surgery. Measurements with the Colvard pupillometer were more reliable and precise than those with the VIVA pupillometer.