Comparison of Predicted Versus Actual Corneal Ablation Depth in Wavefront-guided LASIK and Keratorefractive Lenticule Extraction

Purpose: To compare the predicted and actual corneal ablation depth in wavefront-guided laser in situ keratomileusis (WFG LASIK) and keratorefractive lenticule extraction (KLEx). Methods: This prospective, randomized, contralateral eye study included 26 patients 22 years or older with sphere between −0.75 to −8.00 diopters and 3.00 diopters of cylinder or less undergoing WFG LASIK and KLEx performed by a single surgeon at a large academic hospital. Actual ablation depth was calculated from preoperative and postoperative central corneal thickness. The iDesign aberrometer (Johnson & Johnson Vision) and VisuMax 500 femtosecond laser (Carl Zeiss Meditec AG) were used to derive predicted ablation depth for WFG LASIK and KLEx, respectively. Analyses included t-tests and mixed-effects linear regression. Results: Actual ablation depth was greater than predicted (66.5 ± 27.0 vs 56.3 ± 22.9 µm, P < .001) for WFG LASIK and less than predicted (69.0 ± 25.0 vs 73.6 ± 24.3 µm, P = .04) for KLEx. The difference between actual and predicted ablation depth was −4.6 ± 10.6 µm in KLEx and 10.2 ± 14.8 µm in WFG LASIK ( P < .001). Postoperative spherical equivalent was not significantly different between WFG LASIK and KLEx eyes ( P = .53). LASIK was independently associated with a greater absolute difference between actual and predicted ablation depth compared to KLEx (β: 6.2; 95% CI: 1.7 to 10.7; P = .02). Conclusions: Corneal ablations were deeper than predicted after WFG LASIK and shallower than predicted after KLEx. WFG LASIK was independently associated with greater ablation depth inaccuracy, but there was no difference in postoperative spherical equivalent between WFG LASIK and KLEx.