Effect of Angle Kappa on the Refractive Prediction Accuracy in Cataract Patients After Myopic LASIK/PRK

PURPOSE: To evaluate the impact of angle kappa on prediction accuracy in patients after myopic laser-assisted in-situ keratomileusis (LASIK)/photorefractive keratectomy (PRK). DESIGN: Retrospective, consecutive interventional case-series study. METHODS: This study included 127 postmyopic-LASIK/PRK cataract patients (176 eyes). Three different keratometry (K) values measured by 2 devices were assessed, including simulated keratometry (SimK) obtained by IOLMaster 700 at 2.5 mm ring centered on corneal vertex and SimK derived from Pentacam AXL in 3 mm zone centered on corneal vertex (Pentacam CV) and pupil center (Pentacam PC). The performance of the Barrett True-K formula based on vertex-centered K values (IOLMaster 700; Pentacam CV) and pupil-centered K values (Pentacam PC) was compared. Subgroup analysis was performed using angle kappa (<0.4 mm; ≥0.4 mm). RESULT: The hyperopic prediction error (PE) of the IOLMaster 700 and Pentacam (CV) modes increased with larger angle kappa. Both in total and in eyes with angle kappa <0.4 mm, compared with other modes, the IOLMaster 700 mode showed no systematic bias and relatively lower absolute PE. For eyes with angle kappa ≥0.4 mm, IOLMaster 700 and Pentacam (CV) modes demonstrated hyperopic PE (0.43-0.46 D, P < .05), while the Pentacam (PC) mode displayed no systematic bias, relatively lower mean absolute PE (0.70 D vs 0.90-0.96 D) and the highest percentage of eyes with PE within ±0.5 D (51.22% vs 36.59%-41.46%). CONCLUSION: In postmyopic-LASIK/PRK patients, the prediction accuracy decreased with greater angle kappa when using the corneal vertex-centered K values. The pupil-centered K values were preferred for these patients with angle kappa ≥0.4 mm.