Abstract:  Objective To compare the difference between two optical biometric instruments Pentacam AXL and IOLMaster 500 for measuring the parameters of pseudophakic eyes. Design Prospective cases series. Participants 69 cases (69 eyes) of pseudophakic eyes were selected in October 2021 in Beijing Tongren Hospital. Methods The axial length (AL), keratometry (K1, K2 and Km), anterior chamber depth ACD) and white to white  (WTW) corneal diameter were measured by Pentacam AXL and IOLMaster 500 successively. The results of two groups were tested by paired t test and reliability analysis, and MedCalc software was used to do the Bland-Altman analysis. Main Outcome Measures AL, K1, K2, Km, ACD, WTW, intraclass correlation coefficient(ICC) value, 95% consistency limit of Bland-Altman diagram and points outside the 95% consistency limit. Results AL measured by Pentacam AXL and IOLMaster 500 was (23.57±1.18) mm, (23.58±1.18) mm respectively and K1 was (43.57±2.02) D, (43.65±2.09) D respectively (all P>0.05). The K2 was (44.55±2.04) D, Km was (44.06±2.01) D and WTW was (11.25±0.37) mm measured by Pentacam AXL, which were less than (44.80±2.07) D, (44.23±2.05) D and (11.48±0.38) mm measured by IOLMaster 500 (all P<0.001). ACD (4.14±0.82) mm measured by Pentacam AXL was greater than (3.82±0.59) mm of IOLMaster 500 (t=2.274, P=0.041). The ICC values of AL, K1, K2, and Km were all close to 1 (0.999, 0.990, 0.994, and 0.996 respectively). The 95% consistency limit of Bland-Altman analysis was also close, AL (-0.1345, 0.1039) mm, K1 (-0.9013, 0.7291) D, K2 (-0.8627, 0.3622) D, Km (-0.6815, 0.3451) D, ACD (-0.7055, 1.3397) mm, WTW (-0.7092, 0.2499) mm. Only the points of AL 3.28% (2/61), K1 5.78% (4/69), K2 7.25% (5/69), Km 5.78% (4/69), ACD 0 (0/14) and WTW 5.56% (3/54) were outside the 95% consistency limit. Conclusion There are some differences in axial length, keratometry, anterior chamber depth and white to white of pseudophakic eyes between Pentacam AXL and IOLMaster 500. Measurement results cannot be used instead of each other. （Ophthalmol CHN, 2022, 31: 118-122）

Key words: coherent optical biometrics, pseudophakic eyes, axial length, keratometry, anterior chamber depth, white to white, agreement