AIM:To determine the agreement and repeatability of the pupil measurement obtained with VIP-200(Neuroptics),Power Ref II(Plusoptix),WAM-5500(Grand Seiko) and study the effects of instrument design on pupillometry.METHODS:Forty patients were measured twice in low,mid and high mesopic.Repeatability was analyzed with the within-subject standard deviation(Sw) and paired t-tests.Agreement was studied with Bland-Altman plots and repeated measures ANOVA.Instrument design analysis consisted on measuring pupil size with Power Ref II simulating monocular and binocular conditions as well as with proximity cues and without proximity cues.RESULTS:The mean difference(±standard deviation) between test-retest for low,mid and high mesopic conditions were,respectively:-0.09(±0.16),-0.05(±0.18) and-0.08(±0.23) mm for Neuroptics,-0.05(±0.17),-0.12(±0.23) and-0.17(±0.34) mm for WAM-5500,-0.04(±0.27),-0.13(±0.37) and-0.11(±0.28) mm for Power Ref II.Regarding agreement with Neuroptics,the mean difference for low,mid and high mesopic conditions were,respectively:-0.48(±0.35),-0.83(±0.52) and-0.38(±0.56) mm for WAM-5500,-0.28(±0.56),-0.70(±0.55) and-0.61(±0.54) mm for Power Ref II.The mean difference of binocular minus monocular pupil measurements was:-0.83(±0.87) mm;and with proximity cues minus without proximity cues was:-0.30(±0.77) mm.CONCLUSION:All the instruments show similar repeatability.In all illumination conditions,agreement of Neuroptics with WAM-5500 and Power Ref II is not good enough,which can be partially induced due to their open field design. AIM: To determine the agreement and repeatability of the pupil measurement obtained with VIP-200 (Neuroptics), Power Ref II (Plus optix), WAM-5500 (Grand Seiko) and study the effects of instrument design on pupillometry. METHODS: Forty patients were measured twice in low, mid and high mesopic. Repeatability was analyzed with the within-subject standard deviation (Sw) and paired t-tests. Agility was studied with Bland-Altman plots and repeated measures ANOVA. Instrumentation design analysis consisted on measuring pupil size with Power Ref II simulating monocular and binocular conditions as well as with proximity cues and without proximity cues .RESULTS: The mean difference (± standard deviation) between test-retest for low, mid and high mesopic conditions were, respectively: -0.09 -0.05 (± 0.17), -0.05 (± 0.18) and-0.08 (± 0.23) mm for Neuroptics, -0.05 ± 0.17, -0.12 ± 0.23 and -0.17 ± 0.34 mm for WAM-5500, -0.04 ± 0.27), -0.13 (± 0.37) and -0.11 (± 0.28) mm for Power Ref II.Regarding agreement with Neuroptics, the mean diff erence for low, mid and high mesopic conditions were respectively: -0.48 (± 0.35), -0.83 (± 0.52) and -0.38 (± 0.56) mm for WAM-5500, -0.28 0.55) and -0.61 (± 0.54) mm for Power Ref II. The mean difference of binocular minus monocular pupil measurements was: -0.83 (± 0.87) mm; and with proximity cues minus without proximity cues was: -0.30 mm.CONCLUSION: All the instruments show similar repeatability. In all illumination conditions, agreement of Neuroptics with WAM-5500 and Power Ref II is not good enough, which can be partially induced due to their open field design.