Predictability of Keratorefractive Lenticule Extraction Is Equal to Variance of Preoperative Manifest Refraction Measurement.

Purpose: To compare variance of manifest refraction (MR) measurement and variance of refractive outcomes after keratorefractive lenticule extraction (KLEx) in the same cohort.

Methods: This was a retrospective study of consecutive patients attending at least three preoperative refractions before undergoing KLEx. All manifest refractions were performed according to a standard protocol. Additionally, automated refraction, spectacles prescription, wavefront refraction, and tomography/topography were also considered when determining the treatment refraction. Variance of postoperative outcomes was compared to variance of MR measurement.

Results: The difference in MR of 153 eyes between the first and last preoperative visit showed a mean pairwise absolute difference of 0.22 ± 0.22 diopters (D) (range: 0.00 to 1.25 D) in spherical equivalent (SE). The 95% limit of agreement (LoA) was within 0.73 D for sphere, 0.60 D for cylinder, and 0.61 D for SE. Standard deviation (SD) for corrected distance visual acuity (CDVA) was 0.06 logarithm of the minimum angle of resolution (logMAR) and the 95% LoA was within 1.3 Snellen lines. The differences between reproducibility of the two last preoperative MR and the variance of postoperative outcomes after KLEx (ie, the isolated repeatability of corneal lenticule extraction) was SD of 0.13 D for sphere, cylinder, and SE, and 11 degrees in axis, respectively.

Conclusions: Predictability of KLEx was equal to variance of refraction measurement. Isolated repeatability of the laser treatment was better than the reproducibility of MR. Thus, the authors have shown for the first time that precision of KLEx has reached such a level today that further improvement is limited by MR measurements. [J Refract Surg. 2024;40(11):e814-e823.].