Keratectasia After LASIK
2000; Lippincott Williams & Wilkins; Volume: 26; Issue: 5 Linguagem: Inglês
10.1016/s0886-3350(00)00456-9
ISSN1873-4502
Autores Tópico(s)Glaucoma and retinal disorders
ResumoTheo Seiler has published1,2 and lectured about the occurrence of keratectasia after laser in situ keratomileusis (LASIK).1,2 In a recent guest editorial,3 Seiler reminded us that this feared iatrogenic complication is potentially present in every case of myopic LASIK, especially (but not limited to) those in the higher ranges of myopia. Considering the scarcity of reports about this complication, a question arises: Is Dr. Seiler the only refractive surgeon to whom this happens or “is the currently published number of fewer than 20 cases only the tip of an iceberg”? Yes, Dr. Seiler, they are the very tip of an iceberg. In this sense, I think Dr. Seiler should be recognized for his humility and intellectual honesty. In LASIK, 250 μm remains the gold standard when we consider the thickness of corneal tissue that must be left in place. This is the “security factor,” the paradigm. Nevertheless, biology rarely surrenders entirely to mathematics, and many paradigms of this type have fallen and will fall in the future. This is, after all, the essence of scientific progress. To cite just 1 example: In glaucoma, an intraocular pressure of 21.0 mm Hg was the security factor for many years. But then it became evident that many individuals were biologically sensitive to pressure far lower than this, and the concept of normal-tension glaucoma emerged. Similarly, 250 μm of residual corneal tissue after LASIK will probably suffice for most but not all patients. Without considering the numerous potential sources of error and/or predisposing factors at work in the reported cases of iatrogenic keratectasia (forme fruste keratoconus, inconsistencies in flap thickness, miscalculations, differences in ablation rates in dehydrated stromas, etc.), the undeniable fact is that the tensile strength of corneas will vary among individuals and reducing corneal thickness by 50% or more will weaken the mechanical properties in a way almost completely unknown to us. Finally, the words of Dr. Seiler about stopping and reflecting are a warning that seems absolutely logical and deserves the most judicious consideration. Jorge Muravchik MD Buenos Aires, Argentina
Referência(s)