Comparison of a digital and a handheld infrared pupillometer for determining scotopic pupil diameter

Purpose: To compare a digital infrared pupillometer with a handheld infrared pupillometer for determining scotopic pupil size. Setting: Department of Ophthalmology, Johann Wolfgang Goethe-University, Frankfurt am Main, Germany. Methods: In 100 eyes of 50 healthy individuals (mean age 38.8 years ± 10.7 [SD]), the scotopic pupil size was measured with a digital (Procyon) and a handheld (Colvard) infrared pupillometer. After dark adaptation of 1 minute, measurements were performed with both devices by 2 examiners (E1 and E2). Agreement and repeatability were analyzed using a comparison method described by Bland and Altman. Results: The mean scotopic pupil diameter was 5.90 ± 0.97 mm (range 3.24 to 7.91 mm) with the Procyon and 5.78 ± 0.98 mm (range 3.00 to 7.30 mm) with the Colvard pupillometer. The mean difference between the 2 devices was −0.01 mm (E1) and −0.24 mm (E2). The limits of agreement ranged from 2.84 (E1) to 3.24 (E2). The coefficients of repeatability were 0.64 (Procyon) and 1.16 (Colvard). The mean difference between E1 and E2 was −0.10 for the Procyon and 0.13 for the Colvard pupillometer. The limits of agreement ranged from 1.28 (Procyon) to 2.32 (Colvard). Conclusions: The digital infrared pupillometer (Procyon) demonstrated better repeatability and agreement in measuring scotopic pupil size than a handheld device (Colvard).