Risk factors for ectasia after LASIK

There are some important issues in Binder's recent article1 about risk factors for keratectasia after laser in situ keratomileusis (LASIK) that should be addressed. Binder mentions that “all patients had similar preoperative screenings with new technology testing performed as the equipment became available,” a vague method for screening and excluding patients for refractive surgery. He has performed LASIK in a significant number of patients who had residual stromal beds thinner than 250 μm, central corneal pachymetry less than 500 μm, mean K reading greater than 47 diopters (D), and oblique cylinder greater than 2 D; LASIK surgeons usually avoid doing refractive surgery under these conditions. Keratectasia is a late-onset complication and has been reported even many years after surgery.2–4 What were the author's exclusion criteria for performing LASIK? It is obvious that to evaluate the risk factors for a disease or pathologic condition, you have to examine the involved cases and not just the healthy ones. Even in historical cohort studies, the overall population should be considered; however, in this study, Binder included only the LASIK candidates who were eligible for refractive surgery according to the surgeon's own criteria, which were not mentioned in detail in the article. All eyes that developed keratectasia had abnormal topography, and the author mentions that “if one used those days criteria for abnormal topography, these eyes would have been excluded from having LASIK.” What were “today's criteria for abnormal topography” that the author did not exclude these eyes? Binder concluded, “Individual preoperative and operative factors did not in and of themselves increase the risk for ectasia,” a concept that may encourage other surgeons to perform LASIK in high-risk patients and refer to this article. In conclusion, I think the best way to analyze the risk factors for ectasia is an exact survey of the patients with post-refractive–surgery keratectasia. The abnormal topography seems to be an important risk factor; however, one should also pay attention to other risk factors since LASIK is an elective surgery in healthy eyes.