Reply

Abstract

We thank Wallerstein and Gauvin for the interest in our study.1Ang M. Farook M. Htoon H.M. Mehta J.S. Randomized clinical trial comparing femtosecond LASIK and small-incision lenticule extraction.Ophthalmology. 2020; 127: 724-730Abstract Full Text Full Text PDF PubMed Scopus (37) Google Scholar We reported the refractive predictability at 3 months comparing Small-Incision Lenticule Extraction (SMILE) and femtosecond LASIK in terms of percentage of eyes achieving spherical equivalent within ±0.5 diopter (D) of attempted correction, which was 87% and 92% respectively with a proportional difference of 6%, 95% confidence interval of –5% to 17% (P = 0.26). We had recognized that our prespecified noninferiority margin had been too wide, and thus we elected not to report the noninferiority result, while also acknowledging that a narrower noninferiority margin would have required a far larger trial.1Ang M. Farook M. Htoon H.M. Mehta J.S. Randomized clinical trial comparing femtosecond LASIK and small-incision lenticule extraction.Ophthalmology. 2020; 127: 724-730Abstract Full Text Full Text PDF PubMed Scopus (37) Google Scholar Although sample size estimations for a prespecified hypothesis are important for planning a study, a post hoc analysis as suggested by Wallerstein and Gauvin to analyze a negative result may be problematic.2Gaskill B.N. Garner J.P. Power to the people: power, negative results and sample size.J Am Assoc Lab Anim Sci. 2020; 59: 9-16Crossref PubMed Scopus (24) Google Scholar To estimate the sample size for this study, we used the refractive predictability from a previous publication based on our 10-year audit results (ref 28 in original article). As correctly noted by Wallerstein et al, the trial results were better than the previous published audit, but that is the benefit of hindsight. We also recognized that the numbers required to conduct a superiority trial would have been impractical given our paired-eye study design, a decision further supported by the sparse number of trials using a superiority methodology in refractive surgery over the past 20 years.3Musch D.C. Gillespie B.W. The state of being noninferior.Ophthalmology. 2006; 113: 1-2Abstract Full Text Full Text PDF PubMed Scopus (12) Google Scholar Nonetheless, we did acknowledge that “future studies with a larger sample size and longer follow-up may be useful to establish the superiority of SMILE over LASIK.”1Ang M. Farook M. Htoon H.M. Mehta J.S. Randomized clinical trial comparing femtosecond LASIK and small-incision lenticule extraction.Ophthalmology. 2020; 127: 724-730Abstract Full Text Full Text PDF PubMed Scopus (37) Google Scholar We agree that an optimized nomogram would have benefited both LASIK and SMILE treatments in terms of correcting astigmatism in our study population, as our trial was initiated in 2014 and further improvements have been made in the recommended nomograms from the manufacturer since then (ref 10 in original article). Nonetheless, we found that SMILE and LASIK eyes in our study achieved a 3-month efficacy index of 0.97 ± 0.20 and 0.99 ± 0.20 (P = 0.56), respectively. We thank the authors for pointing out that, since 2014, reported LASIK outcomes from other studies may have further improved with wavefront optimization or topography-guided treatments, making it even more difficult to demonstrate that SMILE is superior or “equivalent.” We had already cautioned against generalizing our study results to other surgeons and populations, which was conducted when SMILE was a relatively newer technique and more surgeon dependent compared with LASIK.1Ang M. Farook M. Htoon H.M. Mehta J.S. Randomized clinical trial comparing femtosecond LASIK and small-incision lenticule extraction.Ophthalmology. 2020; 127: 724-730Abstract Full Text Full Text PDF PubMed Scopus (37) Google Scholar Most surgeons, as we do now, incorporate some form of nomogram while performing SMILE, hence the improvements noted in more recent publications compared to those when the procedure was first started. In summary, we recognize the limitations of our clinical trial while discussing its unique study design and robust follow-up. Although it could not statistically confirm or reject the predefined hypothesis, this fellow-eye trial has provided useful insights into SMILE and LASIK, such as intraoperative experience,4Damgaard I.B. Ang M. Farook M. et al.Intraoperative patient experience and postoperative visual quality after SMILE and LASIK in a randomized, paired-eye, controlled study.J Refract Surg. 2018; 34: 92-99Crossref PubMed Scopus (23) Google Scholar and surgical considerations,5Damgaard I.B. Ang M. Mahmoud A.M. et al.Functional optical zone and centration following SMILE and LASIK: a prospective, randomized, contralateral eye study.J Refract Surg. 2019; 35: 230-237Crossref PubMed Scopus (35) Google Scholar within the context of this study. Re: Ang et al.: Randomized clinical trial comparing femtosecond LASIK and small-incision lenticule extraction (Ophthalmology. 2020;127:724–730)OphthalmologyVol. 127Issue 11PreviewWe commend the authors for undertaking a much needed prospective, paired-eye clinical trial in their article.1 Full-Text PDF