EyeWorld India December 2013 Issue

42 EWAP CORNEA December 2013 central corneal thickness and residual stromal bed are not absolute and should be analyzed on a case-by- case basis along with other factors. There are, however, “other factors that may play a role in ectasia risk,” such as posterior float/ elevation or pachymetric profile analysis as seen in the Pentacam (Oculus, Wetzlar, Germany) software, said Colin Chan, MBBS(Hons), FRANZO , conjoint associate professor, UNSW and Vision Eye Institute, Australia. In a recent study, 3 Dr. Chan and colleagues found some eyes still had apparently normal topography, even after considering the additional topographic measures. “Other factors, genetic and environmental, must be considered. Family history we believe is important and the ideal refractive screening for a young adult would include topography of both parents. Eye rubbing may also be important as it causes chronic biomechanical stress,” he said, especially when a patient has a borderline risk factor score. Surgeons “must be aware of the risk assessment tools for prediction of ectasia when choosing the procedures they recommend their patients undergo,” said Elad Moisseiev, MD , Department of Ophthalmology, Tel Aviv Sourasky Medical Center, Israel. “A potentially high risk for ectasia should outweigh any benefits of LASIK.” And surgeons should remember that even without any risk factors, a patient may develop ectasia. Shifting surgical preferences Dr. Moisseiev and colleagues found that the increased awareness of ectasia has also shifted the bulk of laser vision correction from LASIK to surface ablation, 4 particularly in cases where the ectasia risk is at a risk score of 2 or more. A younger age, increased myopia, and lower residual stromal bed and corneal thickness measurements were all found to be significantly associated with the preference for surface ablation over LASIK, he said. “I do not think central corneal thickness is the most important factor driving the decision, and I personally have no specific cutoff value for it,” he said. “It should be noted that corneal topography is actually the most important factor to consider for risk of ectasia.” Prof. Chan also agrees with the ERSS—“abnormal topography is the most important risk factor for post-LASIK ectasia despite the fact that ectasia can occur even with normal topography. A family history of keratoconus is also an important exclusion factor for LASIK,” he said. In his practice, patients with inferior steepening of more than 1.5 D are usually offered surface ablation instead of LASIK, “but if there are more suspicious signs of forme fruste keratoconus such as irregular astigmatism, elevated and decentered posterior float and thin pachymetry, then we recommend against even a surface ablation.” Prof. Chan believes that “ultimately, other biomolecular markers for ectasia screening need to be developed.” Drs. Ambrosio and Randleman said aspects such as “regional and relational corneal thickness metrics” may be able to provide more information than central corneal thickness readings alone. They wrote, “well-established Placido-based criteria” will remain an integral part of the screening process until technology render those criteria outdated. EWAP References 1. Randleman JB, Woodward M, Lynn MJ, Stulting RD. Risk assessment for ectasia after corneal refractive surgery. Ophthalmol . 2008;115:37-50. 2. Ambrosio R, Randleman JB. Screening for ectasia risk: What are we screening for and when should we screen for it? J Refract Surg . 2013;29(4):230-2. 3. Chan CC, Hodge C, Sutton G. External analysis of the Randleman Ectasia Risk Factor Score System: a review of 36 cases of post-LASIK ectasia. Clin Experiment Ophthalmol. 2010;38:335-40. 4. Moisseiev E, Sela T, Minkev L, Varssano D. Increased preference of surface ablation over laser in situ keratomileusis between 2008-2011 is correlated to risk of ectasia. Clin Ophthalmol . 2013:793-8. Contact information Chan: colin.chan@vgaustralia.com Moisseiev: elad_moi@netvision.net.il Ectasia - from page 40 The 27 th APACRS annual meeting will showcase the latest exciting developments and research in cataract and refractive surgery from the four corners of the globe. It will be held at the thematically designed, fortress-like Fairmont Hotel, Jaipur.