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Corneal Ectasia Risk Score: Statistical Validity and Clinical Relevance

2010; Slack Incorporated (United States); Volume: 26; Issue: 4 Linguagem: Inglês

10.3928/1081597x-20100318-01

1938-2391

Michael W. Belin, Renato Ambrósio,

Ocular Surface and Contact Lens

Guest Editorial freeCorneal Ectasia Risk Score: Statistical Validity and Clinical Relevance Michael W. Belin, MD, ; , MD Renato Ambrósio Jr, MD, PhD, , MD, PhD Michael W. Belin, MD Correspondence: Michael W. Belin, MD, 4232 W Summer Ranch Pl, Marana, AZ 85658-4741. Tel: 518.527.1933; E-mail: E-mail Address: [email protected] and Renato Ambrósio Jr, MD, PhD Published Online:March 18, 2010https://doi.org/10.3928/1081597X-20100318-01Cited by:23PDF ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinkedInRedditEmail SectionsMoreIntroductionIn this issue of the Journal of Refractive Surgery, Binder and Trattler1 retrospectively evaluated the clinical utility of the Ectasia Risk Score System (ERSS) proposed by Randleman et al.2,3 We compliment the authors for tackling a controversial and contentious subject. Since its publication in 2008, the ERSS has been discussed, debated, derided, and disputed at various refractive surgery meetings. Many refractive surgeons believe a disservice was done when these articles,2,3 with such obvious medicolegal implications, were published without accompanying discussions or editorials. Binder and Trattler have intended to correct that omission and put the ERSS into proper clinical perspective.The initial Randleman study2 was well performed, with convincing conclusions based on their preoperative analysis. In their follow-up article with the validation study,3 the ERSS had 8% false negatives and 6% false positives. Many surgeons would consider saying "no" to 6% of their potential LASIK candidates acceptable; this would be a conservative and reasonable approach for preventing the severe complication of iatrogenic ectasia. Of issue, however, are 1) the 8% of cases that developed ectasia despite low ERSS score, and 2) a false positive rate as high as 35% if a relatively young population is evaluated.4The original ERSS study3 has been touted as being a statistically validated study. Statistical validity and clinical applicability, however, are not always interchangeable.Practitioners need to carefully evaluate every study to determine whether the parameters utilized are representative of their practice patterns. If not, conclusions drawn from that particular study, regardless of its statistical validity, may not be correctly applied to their patients. Most readers are not statisticians and cannot explain the difference between a Chi-square analysis and Student t test or know when to apply a logistic regression analysis or use odds ratio estimates.2,3 Readers, however, should appreciate that statistics alone cannot legitimize the clinical utility of a study.Much of the criticisms lodged against the ERSS relate to the high risk score assigned to patient age. If the screening techniques used are incomplete (eg, anterior curvature), other parameters (eg, age) may have an exaggerated significance that would lessen with more sensitive screening (eg, posterior elevation and pachymetric progression).5,6 Keratoconus is a disease that typically presents in the late teens and/or twenties. A truly new case of keratoconus (excluding iatrogenic) presenting past the fourth decade is rare. If we were able to identify early disease with 100% specificity and sensitivity, age would be of little concern. For example, if you use 1) three-dimensional tomographic reconstruction of the corneal surface and evaluate the posterior corneal surface, and 2) full pachymetric spatial profile as opposed to just a single central data point, this would change the risk analysis.5–7Our criticisms fall on how the Randleman study has been applied. The study was based on a single central ultrasound reading and anterior curvature analysis. We believe this represents an incomplete analysis for ectasia risk and/or susceptibility, and is not reflective of screening parameters used by many refractive surgeons. Binder and Trattler's article reveals some shortcomings of applying the ERSS to a large refractive surgery practice.At the 2009 International Society of Refractive Surgery symposium in Barcelona (European Society of Cataract and Refractive Surgery Annual Meeting 2009), the audience was polled, with most regularly examining the posterior corneal surface and pachymetric map as part of their refractive screening. There is no question that eyes can exhibit normal anterior curvature and central corneal thickness but have clear evidence of subclinical keratoconus when viewed with full tomo-graphic analysis (Fig 1).5 Other clinical examples demonstrate how additional parameters, when considered, can alter the risk analysis (Fig 2). Patients who have normal videokeratoscopy and a negative keratoconus screening by both Klyce/Maeda or Smolek/Klyce analysis may fall outside of two standard deviations from published norms for elevation and corneal thickness when examined by corneal tomography.8,9 The above examples reveal the potential for false negatives but, as noted, may explain the reason for age being such a significant ERSS risk factor.Figure 1. Four examples of refractive composite maps (anterior curvature, anterior elevation, posterior elevation, corneal thickness) (Pentacam; Oculus Optikgeräte GmbH, Wetzlar, Germany), each demonstrating abnormalities that would be missed using the screening parameters/examination used in the Ectasia Risk Score System. The upper left map shows a significant posterior paracentral island of elevation indicative of ectasia despite a normal curvature (low symmetric astigmatism) and a central corneal thickness of 514 µm. The upper right map reveals significant inferior posterior ectasia and an accompanying displacement of the thinnest point to the ectatic region despite normal anterior curvature and a normal central thickness. Similarly, the lower left map shows a low degree of astigmatism on anterior curvature but an ectatic region on the posterior elevation with mild displacement of the thinnest point. The lower right map demonstrates that although the anterior and posterior surfaces can appear normal (low degree of astigmatism on both elevation and curvature), the corneal thickness map may be abnormal. The thinnest point is significantly displaced.Figure 2. Corneal topography of a 30-year-old female candidate for LASIK. Spherical equivalent refraction is −5.00 D, central corneal thickness (CCT) is 513 µm in the right eye and 502 µm in the left eye. The Ectasia Risk Score System score would be zero in the right eye and 2 in the left eye (CCT = 502 µm). A) Normal anterior curvature axial map, normal keratoscope image, and no keratoconus pattern are detected based on both the Klyce/Maeda and Smolek/Klyce programs (Tomey TMS; Tomey Corp, Nagoya, Japan). B) Anterior and posterior elevation, corneal thickness and thinnest point displacement, and thickness spatial profile maps (Pentacam; Oculus Optikgeräte GmbH, Wetzlar, Germany). Regression analysis of these five parameters shows this cornea to be 2.38 standard deviations from the norm, which is suspicious for ectasia susceptibility. Enhanced posterior elevation is 11 µm (upper limit for green), and the graph for Percentage of Thickness Increase (PTI) demonstrates an escape from the norm, starting at the 4-mm diameter.Binder and Trattler1 discuss the limitations of commonly performed residual stromal bed computation. Their discussion deals with the operative parameters of flap thickness variability and the consequences of not performing intraoperative pachymetry. We previously published our results in approximately 1400 eyes comparing central thickness to thinnest point readings and showed a potential source of error in magnitude equal or greater than that seen with flap variability.6 We suggest, in addition to the intraoperative recommendations made by Binder and Trattler, that all pre- operative residual stromal bed computations be based on the thinnest preoperative reading.In addition, a more complete understanding of the physical and biomechanical properties of the cornea will allow an improved determination of an individual's predisposition or susceptibility for developing ectasia. Current corneal tomography techniques available include Scheimpflug imaging, optical coherence tomography, and high-frequency ultrasound. Although these diagnostic tests are in routine use, and screening parameters and normal values have been published, large scale, long-term studies to determine corneal tomography's ability to better identify the possible risk of developing ectasia are lacking. Such studies are required to clinically validate our views.It is difficult at times to read the scientific literature and determine whether a well performed study has clinical applicability. Most physicians do not have the time, proclivity, or database to carefully analyze each study to determine its clinical relevance.10 Binder and Trattler are commended for performing such an exhaustive review. Statistics, probabilities, means, modes, and standard deviations are all wonderful tools, but should not be a substitute for careful analysis for clinical relevance.1.Binder PS, Trattler WB. Evaluation of a risk factor scoring system for corneal ectasia after LASIK in normal eyes. J Refract Surg. 2010; 26(4):241–250. LinkGoogle Scholar2.Randleman JB, Woodward M, Lynn MJ, Stulting RD. Risk assessment for ectasia after corneal refractive surgery. Ophthalmology. 2008; 115(1):37–50. Crossref MedlineGoogle Scholar3.Randleman JB, Trattler WB, Stulting RD. Validation of the Ectasia Risk Score System for preoperative laser in situ keratomileusis screening. Am J Ophthalmol. 2008; 145(5):813–818. Crossref MedlineGoogle Scholar4.Duffey RJ, Hardten DR, Lindstrom RL, Probst LE, Schanzlin DJ, Tate GW, Wexler SA. Ectasia after refractive surgery. Ophthalmology. 2008; 115(10):1849; author reply 1015–1016. Crossref MedlineGoogle Scholar5.Belin MW, Khachikian SS. An introduction to understanding elevation-based topography: how elevation data are displayed—a review. Clin Experiment Ophthalmol. 2009; 37(1):14–29. Crossref MedlineGoogle Scholar6.Belin MW, Khachikian SS. New devices and clinical implications for measuring corneal thickness. Clin Experiment Ophthalmol. 2006; 34(8):729–731. Crossref MedlineGoogle Scholar7.Khachikian SS, Belin MW, Ciolino JB. Intrasubject corneal thickness asymmetry. J Refract Surg. 2008; 24(6):606–609. LinkGoogle Scholar8.Khachikian SS, Belin MW. Posterior elevation in keratoconus. Ophthalmology. 2009; 116(4):816, 816.e1; author reply 816–817. Crossref MedlineGoogle Scholar9.Ambrósio R, Alonso RS, Luz A, Coca Velarde LG. Corneal-thickness spatial profile and corneal-volume distribution: tomographic indices to detect keratoconus. J Cataract Refract Surg. 2006; 32(11):1851–1859. Crossref MedlineGoogle Scholar10.Liesegang TJ. Peer review should continue after publication. Am J Ophthalmol. 2010; 149(3):359–360. Crossref MedlineGoogle Scholar Previous article Next article FiguresReferencesRelatedDetailsCited by Mohammadpour M, Heidari Z, Hashemi H, Yaseri M and Fotouhi A (2022) Comparison of Artificial Intelligence-Based Machine Learning Classifiers for Early Detection of Keratoconus, European Journal of Ophthalmology, 10.1177/11206721211073442, 32:3, (1352-1360), Online publication date: 1-May-2022. Brar S, Sriganesh S, Sute S, Ganesh S and Meduri A (2022) Comparison of Long-Term Outcomes and Refractive Stability following SMILE versus SMILE Combined with Accelerated Cross-Linking (SMILE XTRA), Journal of Ophthalmology, 10.1155/2022/4319785, 2022, (1-9), Online publication date: 28-Feb-2022. Brar S, Roopashree C and Ganesh S (2021) Incidence of Ectasia After SMILE From a High-Volume Refractive Surgery Center in India, Journal of Refractive Surgery, 37:12, (800-808), Online publication date: 1-Dec-2021. Formisano N, Putten C, Grant R, Sahin G, Truckenmüller R, Bouten C, Kurniawan N and Giselbrecht S (2021) Mechanical Properties of Bioengineered Corneal Stroma, Advanced Healthcare Materials, 10.1002/adhm.202100972, 10:20, (2100972), Online publication date: 1-Oct-2021. Xie Y, Zhao L, Yang X, Wu X, Yang Y, Huang X, Liu F, Xu J, Lin L, Lin H, Feng Q, Lin H and Liu Q (2020) Screening Candidates for Refractive Surgery With Corneal Tomographic–Based Deep Learning, JAMA Ophthalmology, 10.1001/jamaophthalmol.2020.0507, 138:5, (519), Online publication date: 1-May-2020. Faria-Correia F, Ambrosio Jr R, Esporcatte L, Salomão M, Sena Jr. N, Haddad J and Dawson D (2020) Multimodal Imaging in Refractive Surgery, Highlights of Ophthalmology, 10.5005/hooe-48-4-4, 48:4ENG, (4-24), Online publication date: 1-Aug-2020. Esporcatte D, Salomão D, Sena Jr. D, Haddad D, Dawson D, Faria-Correia D and Ambrósio Jr D (2020) Imágenes Multimodales en la Cirugía Refractiva, Highlights of Ophthalmology, 10.5005/hoos-48-4-4, 48:4ESP, (4-24), Online publication date: 1-Aug-2020. Daxer A (2017) MyoRing treatment of myopia, Journal of Optometry, 10.1016/j.optom.2016.06.003, 10:3, (194-198), Online publication date: 1-Jul-2017. Vahdati A, Seven I, Mysore N, Randleman J and Dupps W (2016) Computational Biomechanical Analysis of Asymmetric Ectasia Risk in Unilateral Post-LASIK Ectasia, Journal of Refractive Surgery, 32:12, (811-820), Online publication date: 1-Dec-2016. Wolle M, Randleman J and Woodward M (2016) Complications of Refractive Surgery, International Ophthalmology Clinics, 10.1097/IIO.0000000000000102, 56:2, (127-139), . Wahba S, Roshdy M, Elkitkat R and Naguib K (2016) Rotating Scheimpflug Imaging Indices in Different Grades of Keratoconus, Journal of Ophthalmology, 10.1155/2016/6392472, 2016, (1-9), . Padmanabhan P, Rachapalle Reddi S and Sivakumar P (2016) Topographic, Tomographic, and Aberrometric Characteristics of Post-LASIK Ectasia, Optometry and Vision Science, 10.1097/OPX.0000000000000922, 93:11, (1364-1370), Online publication date: 1-Nov-2016. Correia F and Ambrósio R (2014) Queratocono subclínico: importancia de los factores morfológicos y biomecánicos en su detección precoz Biomecánica y arquitectura corneal, 10.1016/B978-84-9022-649-0.50023-5, (197-204), . Steinberg J, Kohl C, Katz T, Richard G and Linke S (2013) Differenz und Entfernung zwischen zentraler und dünnster Stelle der HornhautDifference and distance between the central and thinnest points of the cornea, Der Ophthalmologe, 10.1007/s00347-013-2892-0, 111:4, (339-347), Online publication date: 1-Apr-2014. Ambrósio R and Randleman J (2013) Screening for Ectasia Risk: What Are We Screening For and How Should We Screen For It?, Journal of Refractive Surgery, 29:4, (230-232), Online publication date: 1-Apr-2013. Gilani F, Cortese M, Ambrósio R, Lopes B, Ramos I, Harvey E and Belin M (2013) Comprehensive anterior segment normal values generated by rotating Scheimpflug tomography, Journal of Cataract and Refractive Surgery, 10.1016/j.jcrs.2013.05.042, 39:11, (1707-1712), Online publication date: 1-Nov-2013. Smadja D (2013) Topographic and Tomographic Indices for Detecting Keratoconus and Subclinical Keratoconus: A Systematic Review, International Journal of Keratoconus and Ectatic Corneal Diseases, 10.5005/jp-journals-10025-1052, 2:2, (60-64), Online publication date: 1-Aug-2013. Ambrósio R, Faria-Correia F, Ramos I, Valbon B, Lopes B, Jardim D and Luz A (2013) Enhanced Screening for Ectasia Susceptibility Among Refractive Candidates: The Role of Corneal Tomography and Biomechanics, Current Ophthalmology Reports, 10.1007/s40135-012-0003-z, 1:1, (28-38), Online publication date: 1-Mar-2013. Colin J, Smadja D and Touboul D (2012) Comparative Evaluation of Elevation, Keratometric, Pachymetric and Wavefront Parameters in Normal Eyes, Subclinical Keratoconus and Keratoconus with a Dual Scheimpflug Analyzer, International Journal of Keratoconus and Ectatic Corneal Diseases, 10.5005/jp-journals-10025-1031, 1:3, (158-166), Online publication date: 1-Dec-2012. Ramos I, Correia F, Lopes B, Salomão M and Correa R (2012) Topometric and Tomographic Indices for the Diagnosis of Keratoconus, International Journal of Keratoconus and Ectatic Corneal Diseases, 10.5005/jp-journals-10025-1018, 1:2, (92-99), Online publication date: 1-Aug-2012. Pieh S (2011) Oberflächenbehandlung Refraktive Chirurgie, 10.1007/978-3-642-05406-8_9, (121-136), . Ruberti J, Sinha Roy A and Roberts C (2011) Corneal Biomechanics and Biomaterials, Annual Review of Biomedical Engineering, 10.1146/annurev-bioeng-070909-105243, 13:1, (269-295), Online publication date: 15-Aug-2011. Elkitkat R, Badran T and Ebeid W (2021) Revisiting the Robustness of Pentacam HR Indices Against Soft Contact Lens Wear, Clinical Ophthalmology, 10.2147/OPTH.S308560, Volume 15, (1573-1581) Request Permissions InformationCopyright 2010, SLACK IncorporatedPDF downloadCorrespondence: Michael W. Belin, MD, 4232 W Summer Ranch Pl, Marana, AZ 85658-4741. Tel: 518.527.1933; E-mail: [email protected]comFrom the University of Arizona & Southern Arizona Veterans Administration Healthcare System, Tucson, Ariz (Belin); and Instituto de Olhos Renato Ambrosio, Rio de Janeiro Corneal Tomography & Biomechanics Study Group, Rio de Janeiro, Brazil (Ambrósio).The authors are consultants to Oculus Optikgeräte GmbH (Wetzlar, Germany).