Myopic Laser Corneal Refractive Surgery Reduces Interdevice Agreement in the Measurement of Anterior Corneal Curvature

Objectives: To investigate interdevice differences and agreement in the measurement of anterior corneal curvature obtained by different technologies after laser corneal refractive surgery. Methods: The prospective study comprised 109 eyes of 109 consecutive patients who had undergone laser-assisted in situ keratomileusis (LASIK). Preoperative and postoperative corneal parameters were measured by Scheimpflug imaging (Pentacam), Placido-slit-scanning (Orbscan) and auto-keratometry (IOLMaster). Preoperative and postoperative anterior corneal curvatures (K readings) were compared between devices. Inter-device agreement was evaluated by Bland-Altman analysis. Results: Preoperatively, the difference of K reading for Pentacam-IOLMaster (0.04 +/- 0.20 D) was not statistically significant (P=0.059). The differences between Pentacam-Orbscan and Orbscan-IOLMaster were 0.20 +/- 0.34 D (P<0.001)and -0.17 +/- 0.29 D (P<0.001), respectively. After surgery, no difference was found for Pentacam-Orbscan (0.05 +/- 0.38, P=0.136). The differences between Pentacam-IOLMaster and Orbscan-IOLMaster were 0.13 +/- 0.29 D (P<0.001) and 0.19 +/- 0.34 D (P<0.001). Preoperative interdevice agreement (95% limit of agreement [LOA]) between Pentacam and Orbscan, Pentacam and IOLMaster, and Orbscan and IOLMaster were 1.31 D, 0.79 D and 1.14 D, respectively. The 95% LOAs decreased to 1.47 D, 1.14 D, and 1.34 D after refractive surgery. Conclusion: Corneal refractive surgery changed the preoperative and postoperative interdevice differences in corneal curvature measurements and reduced interdevice agreement, indicating that the devices are not interchangeable.