Objective: To compare the consistency of Kappa Angle measurements in patients with age-related cataracts using four instruments of different principles in a dark room. Methods: Sixty cases (60 eyes) of age-related cataract were adapted in the darkroom for 10 minutes. The pupil size and angle Kappa were measured by iTrace, Pentacam HR, Lenstar900 and IOLMaster700. One-way ANOVA test and Kruskal-Wallis nonparametric test were used to compare the measured data among the four instruments, and Bland-Altman analysis was used for consistency comparison. Results: The measured pupil diameters of iTrace, Pentacam HR, Lenstar900 and IOLmaster700 were 4.64±0.71 mm, 2.96±0.47 mm, 4.86±0.76 mm and 4.66±0.92 mm. The Angle Kappa sizes were 0.227±0.121 mm, 0.161± 0.09 mm, 0.2±0.124 mm, 0.203±0.104 mm. The proportion of angle Kappa larger than 0.5 mm was 3.33%, 3.33%, 1.67% and 1.67%. The measurement results of angle Kappa between Pentacam and iTrace were statistically significant (P=0.001). There was no significant difference in the measurement results of angle Kappa between Pentacam and Lenstar900, Pentacam HR and IOL-Master700 (P=0.044, 0.036). There was no significant difference in the results of angle Kappa measurement among the other three instruments. The subjective score of light intensity in the process of measurement of iTrace, Pentacam HR, Lenstar900 and IOLMaster700 showed that during the process of measurement, 60 cases (100%) experienced obvious discomfort caused by the light intensity in Pentacam HR, while 40 cases (66.67%) felt comfort in IOLMaster700. The differences among the subjective score of light intensity of four instruments were statistically significant (P<0.001). Conclusion: The consistency of the measurement results of Kappa angle between Pentacam HR and iTrace, Lenstar900, IOLMaster700 in the darkroom is relatively poor, so it is necessary to be careful to replace them in clinic.