IOL Power Calculation after Refractive Surgery

Abstract

We read with great interest the paper by McCarthy et al1McCarthy M. Gavanski G.M. Paton K.E. Holland S.P. Intraocular lens power calculations after myopic laser refractive surgery: a comparison of methods in 173 eyes.Ophthalmology. 2011; 118: 940-944Abstract Full Text Full Text PDF PubMed Scopus (98) Google Scholar concerning intraocular lens (IOL) power calculation after refractive corneal surgery published in the May 2011 issue. They undertook significant effort to perform such a study in a large number of patients, and we congratulate them. We would like to thank them because they tested, among the others, the method we previously described (R factor). Unfortunately, we found some errors in the paper. First, they included our method among those that require information from the prior laser surgery and named these methods “historical.” Unfortunately, this is not true, as our method2Rosa N. Capasso L. Romano A. A new method for calculating intraocular lens power after photorefractive keratectomy.J Refract Surg. 2002; 18: 720-724PubMed Google Scholar does not require knowledge of the history of the patient, and to the best of our knowledge, was the first among such methods to be published, (maybe for this it could be named historical). In fact, it relies on a correcting factor (R factor) calculated with the following formula: R= 0.0276*AL + 0.3635 where AL is the axial length. This factor has to be multiplied by the patient's corneal radius, so it is clear that the history of the patient is not needed. In the methods section, they do not clarify how they calculated the R factor, and as they describe it as historical, we are afraid that they have miscalculated it leading to uncertainties in their findings and/or conclusions. According to the Table they published, it appears they utilized this correcting factor with SRKT, HofferQ, and Holladay formulas. Actually, in our first paper on this topic, we suggested using this correcting factor with either SRK T or Holladay 1 formulas, but in 2009 we published another paper,3Rosa N. Capasso L. Lanza M. Borrelli M. Clinical results of a corneal radius correcting factor in calculating intraocular lens power after corneal refractive surgery.J Refract Surg. 2009; 25: 599-603PubMed Google Scholar in which we suggested that this correcting factor should be used with SRKT in cases of eyes with an axial length (AL) <30 mm but in eyes with an AL >30 mm, it should be used with both SRKT and SRK II and the results should be averaged. In this way, we can avoid excessive hypercorrections in these long eyes. We are curious to know if the authors could comment on our clarifications, and we hope they can explain if our comments lead to any changes or clarifications in the authors very good work. Intraocular Lens Power Calculations after Myopic Laser Refractive Surgery: A Comparison of Methods in 173 EyesOphthalmologyVol. 118Issue 5PreviewTo evaluate and compare published methods of intraocular lens (IOL) power calculation after myopic laser refractive surgery in a large, multi-surgeon study. Full-Text PDF