Abstract
This study aims to assess the agreement between the Pentacam AXL and IOL Master 500 in measuring biometric components and intraocular lens (IOL) power in patients with keratoconus (KCN). In this cross-sectional study, individuals aged over 60 years were randomly selected from 22 districts in Tehran. Inclusion criteria were individuals over 60 years of age, the absence of ocular pathologies aside from KCN and cataracts, no prior ocular surgeries, and no systemic diseases. Optical biometry was conducted for each eye utilizing both the Pentacam AXL and IOL Master 500 devices, with IOL power determined through six formulas: Kane keratoconus, Barret universal 2, Holladay 1, Haigis, Hoffer Q, and SRK/T, based on the biometric data acquired from each device. The agreement between the biometric measurements from the two devices and the calculated IOL powers was analyzed using the Bland-Altman method. A total of 121 eyes from 121 patients with keratoconus were examined in this study. Among these participants, 76 (62.8%) were female. The average age of the individuals was 67.66 ± 6.47 years. The 95% limits of agreement for axial length measurements, as well as K1, K2, ACD, and WTW, between the IOL Master 500 and the Pentacam AXL were recorded as -0.08 to 0.02, -1.28 to 0.79, -1.83 to 1.06, -0.16 to 0.34, and - 0.96 to 0.13, respectively. Among the six formulas utilized for calculating IOL power, a significant difference was observed between the two devices, with the Pentacam AXL consistently yielding higher power values. The most pronounced difference was noted with the Hoffer Q formula, which showed a variation of + 0.55 ± 0.92, whereas the Holladay 1 formula exhibited the least difference at + 0.34 ± 1.98. The 95% limits of agreement for IOL power calculations between the two devices, based on the Kane keratoconus, SRK/T, Hoffer Q, Barrett Universal 2, Holladay 1, and Haigis formulas, were recorded as -1.14 to 2.00, -1.16 to 2.00, -1.25 to 2.37, -1.06 to 2.12, -1.20 to 2.21, and -1.01 to 2.23 respectively. The Pentacam AXL and IOL Master 500 demonstrate a good agreement in their axial length measurements. Nonetheless, discrepancies in keratometry, anterior chamber depth, and white-to-white measurements between the two devices result in variations in IOL power calculations. Additionally, the choice of formula utilized for these calculations further influences the determined power, with values obtained from the Pentacam AXL in conjunction with the Kane keratoconus formula yielding higher power estimates.