Wavefront-Guided LASIK and Preoperative Higher Order Aberrations.

We read with interest the article by Kung and Manche in the April 2016 issue.1 In the first part of the article, they explained that most studies seemed to suggest that the wavefront-guided excimer laser procedures were slightly superior than wavefront-optimized approaches, particularly in patients with preoperative root mean square (RMS) of higher order aberrations (HOAs) less than 0.3 μm. However, the two cited publications by the authors (the prospective, open-label, multicenter study conducted by Stonecipher and Kezirian2 and the meta-analysis by Feng et al.3) reported exactly the opposite: if the magnitude of preoperative RMS was greater than 0.3 μm, wavefront-guided ablation had a significantly better postoperative aberration profile than wavefront-optimized ablation and, on the other hand, wavefront-guided treatments had no clear advantage over wavefront-optimized treatments in eyes with preoperative RMS lower than 0.3 μm.2,3 Kung and Manche found that the two platforms produced similar self-reported symptoms in patients with RMS aberrations greater than 0.3 μm but, in eyes with RMS aberrations less than 0.3 μm, the wavefrontguided platform resulted in higher self-reported “excellent vision” and significantly fewer adverse effects (eg, problems with daytime and nighttime clarity and visual fluctuation).1 However, the authors did not report an analysis on the postoperative aberration profile comparing the two subgroups: those with HOAs higher than 0.3 μm and those with less than that magnitude of aberrations. The findings on visual symptoms are counterintuitive because one would expect the impact of customized aberration correction to be higher in the group with higher preoperative aberrations, as shown in the other studies. We think that the numbers deserve to be rechecked to ensure that there are not any inaccuracies in the capture or analysis of the data. In addition, in Table 3 there seems to be confusion in the presentation of the information. It shows in the first column of each group, under a heading that says logMAR, data on manifest sphere, cylinder, and spherical equivalent, which units are in diopters. However, they are converted to “Snellen visual acuities.” Undoubtedly it is a mistake. The same occurs with the aberrometry data. The text referring to the Table 3 is not clear either. It says: “Postoperative measurements of visual acuity showed that manifest sphere (wavefront-guided vs wavefront-optimized: -0.32 vs -0.56; P = .0001, significant) and manifest spherical equivalent refraction (wavefront-guided vs wavefront-optimized: -0.18 vs -0.41; P = .0001, significant) were superior in the wavefront-optimized group (Table 3).” Manifest sphere and spherical equivalent are not visual acuity measurements, but refractive error determinations. If the postoperative refractive error was smaller, as is shown, in the wavefront-guided group of eyes, the statement made in the text is not correct. It is essential that the authors clarify these critical points so that we as readers can have a better understanding of the results of this interesting study.