Abstract
OBJECTIVES: To compare the accuracy of two different corneal refractive power measurements in intraocular lens (IOL) power calculation in post-myopic-LASIK eyes. METHODS: Post-myopic-LASIK patients scheduled for cataract surgery were enrolled. Corneal refractive power centred on corneal apex (K(apex)) and pupil centre (K(pupil)), decentration of ablation zone, and Kappa angle were measured by Pentacam. Predicted postoperative spherical equivalence (SE) was calculated using K(apex) and K(pupil), respectively. Prediction error was calculated as actual SE minus predicted SE. Mean error (ME), mean absolute error (MAE), and median absolute error (MedAE) were compared between K(apex) and K(pupil) groups, with subgroup analysis in terms of decentred ablation and Kappa angle. RESULTS: Totally 92 eyes were analysed. ME, MAE and MedAE with K(apex) were all lower than those with K(pupil) (-0.42 ± 1.06 vs -0.64 ± 1.21 D, 0.89 ± 0.71 vs 1.01 ± 0.92 D, 0.69 vs 0.76 D, respectively; P < 0.05 for ME and MedAE). In both subgroups of larger decentration of ablation zone and larger Kappa angle, ME with K(apex) was lower than that with K(pupil) to a higher degree (both P < 0.05). Average K(apex) was higher than average K(pupil) (P < 0.001). Multivariate analysis demonstrated that prediction error with K(pupil) was associated with decentration of ablation zone (β = -0.264, P = 0.019), while no such association was found in prediction error with K(apex). CONCLUSIONS: The K(apex) achieved better accuracy in IOL power calculation than K(pupil) in post-myopic-LASIK eyes, especially in eyes with large decentration of ablation zone or large Kappa angle.