Ablation-Guided K Measurements Improve the Accuracy of IOL Power Calculation After Clinically Decentered Myopic LASIK.

PURPOSES: Define clinical ablation decentration and construct personalized areas for K measurements to improve the accuracy of intraocular lens (IOL) power calculation after myopic laser in situ keratomileusis (LASIK).

DESIGN

Retrospective, observational case series.

METHODS

Ablation areas were delineated on smoothed corneal topographies (Pentacam AXL). Personalized areas for K measurements were constructed as the overlap between the corneal ablation area and a given apex-centered circle. K values were calculated on these personalized areas using the ring or zone method. Ablation decentration was evaluated by (1) index P: the percentage of the personalized area in the corresponding circle, and (2) index D: the distance from its maximum inscribed circle center to the corneal apex. Their absolute predictive errors (AE) were compared with those of IOLMaster-reported K in 60 cataract eyes from 48 patients with prior LASIK.

RESULTS

Ablation-guided K values derived from the 3.5 mm-diameter circle and the ring methods, namely K3.5ring, had the best predictive accuracy (Mean AE = 0.64D, Median AE = 0.47D). This method had better performance with smaller index P (ρ = -0.473, P = .006) and larger index D (ρ = 0.432, P = .014). Personalized areas with index P < 95.02% (P = .013) or index D ≥ 1.0975 mm (P = .007) showed greater accuracy improvements, and were defined as clinical ablation decentration.

CONCLUSIONS

This study developed a novel ablation-guided K measurement method for IOL calculation in eyes with clinically decentered myopic ablation. We also provide a ready-to-use tool (https://boluo-baba-ablation-guided-k-measurements.share.connect.posit.cloud) based on this method for clinical convenience.