Effects of Ocular Residual Astigmatism on Refractive Outcomes for Myopia Correction After Keratorefractive Lenticule Extraction Surgery.

Purpose: To evaluate the effects of ocular residual astigmatism (ORA) on refractive outcomes for patients with astigmatism after keratorefractive lenticule extraction (KLEx) and to identify the ratio of the ORA/manifest refractive cylinder at the corneal plane (MRC) resulting in a greater index of success (IOS).

Methods: In total, 892 right eyes that underwent KLEx surgery were included. Astigmatic changes were evaluated using Alpins' vector analysis. Surgical outcomes grouped by ORA/MRC and ORA were compared. In stage 1, eyes were divided into two groups with an ORA/MRC cutoff value of 1. In stage 2, patients with an ORA/MRC ratio of greater than 1 were divided into two groups: those with an ORA of 1.25 diopters (D) or greater and those with an ORA of less than 0.50 D. ORA/MRC thresholds leading to a high IOS were analyzed using receiver operating characteristic (ROC) curves.

Results: In stage 1, the mean IOS was 0.13 and 0.21 for the low and high ORA/MRC groups, respectively (P < .001). In stage 2, for high ORA/MRC, the IOS was significantly greater when the ORA was greater than 1.25 D than when the ORA was less than 0.50 D (0.27 versus 0.13, P < .001). ROC curves revealed that participants with an ORA/MRC ratio of greater than 1.8 were more likely to have a higher IOS (P < .001).

Conclusions: Patients with a smaller ORA can obtain better correction results. An ORA/MRC ratio of greater than 1.8 may increase the risk of poor astigmatism correction with KLEx. The application of vector planning may improve the refractive outcomes of KLEx. [J Refract Surg. 2024;40(12):e966-e973.].