Re: McNabb et al.: Optical coherence tomography accurately measures corneal power change from laser refractive surgery (Ophthalmology 2015;122:677-86)

Abstract

I read with interest the article by McNabb et al1McNabb R.P. Farsiu S. Stinnett S.S. et al.Optical coherence tomography accurately measures corneal power change from laser refractive surgery.Ophthalmology. 2015; 122: 677-686Abstract Full Text Full Text PDF PubMed Scopus (24) Google Scholar regarding the measurement of corneal power in eyes that have undergone refractive surgery. One of the study's limitations was that myopic and hyperopic eyes were analyzed in a single group. It is known that after refractive surgery there is an overestimation of the corneal power in the eyes that had surgery for myopia,2Rosa N. Capasso L. Lanza M. et al.Reliability of the IOL Master in measuring corneal power changes after photorefractive keratectomy.J Cataract Refract Surg. 2004; 30: 409-413Abstract Full Text Full Text PDF PubMed Scopus (26) Google Scholar, 3Rosa N. Furgiuele D. Lanza M. et al.Correlation of changes in refraction and corneal topography after photorefractive keratectomy.J Refract Surg. 2004; 20: 478-483PubMed Google Scholar and there is an underestimation of the power of the cornea in eyes that had surgery for hyperopia.4Rosa N. De Bernardo M. Borrelli M. et al.Reliability of the IOLMaster in measuring corneal power changes after hyperopic photorefractive keratectomy.J Refract Surg. 2011; 27: 293-298Crossref PubMed Scopus (17) Google Scholar Evaluating the overall differences in corneal power for both refractive defects may introduce bias in assessing the accuracy of the variations before and after surgery. In the characteristics of the patients examined listed in the article, furthermore, the description of the preoperative refractive error is lacking: statistical analysis was performed by comparing the differences between the refractive changes calculated at the corneal vertex and the variations in corneal power measured by different devices. If, from a statistical point of view, all this is correct, it must be emphasized that it is shown that the underestimation of corneal power in myopic eyes is most evident in eyes with a higher preoperative refractive defect.2Rosa N. Capasso L. Lanza M. et al.Reliability of the IOL Master in measuring corneal power changes after photorefractive keratectomy.J Cataract Refract Surg. 2004; 30: 409-413Abstract Full Text Full Text PDF PubMed Scopus (26) Google Scholar, 3Rosa N. Furgiuele D. Lanza M. et al.Correlation of changes in refraction and corneal topography after photorefractive keratectomy.J Refract Surg. 2004; 20: 478-483PubMed Google Scholar I believe the conclusions of the article could cause confusion and be of limited practical use without information about preoperative refractive errors. Optical Coherence Tomography Accurately Measures Corneal Power Change from Laser Refractive SurgeryOphthalmologyVol. 122Issue 4PreviewTo determine the ability of motion-corrected optical coherence tomography (OCT) to measure the corneal refractive power change due to LASIK. Full-Text PDF ReplyOphthalmologyVol. 123Issue 1PreviewWe thank Dr Lanza for his comments on our article in which we described the use of optical coherence tomography (OCT) to accurately measure corneal refractive power change after laser refractive surgery. As Dr Lanza notes, it has previously been shown that using automated or simulated keratometry, there is an underestimation of corneal power change using these keratometric techniques after myopic laser refractive surgery with the error increasing as the myopic correction increased.1–3 In the hyperopic population, the error was more variable depending on the amount of correction and duration of follow-up. Full-Text PDF