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Findings from a retrospective analysis including 81,715 consecutive LASIK-treated eyes provide no evidence after 12 to 24 months of follow-up that a "thin cornea" increases the risk for postoperative ectasia.
The study includes patients who underwent LASIK at Optical Express from April 2008 through March 2009. All patients treated had normal preoperative corneal topography based on assessment using a Scheimpflug system.
About 2.5% of the total population, 2,181 eyes (1,479 patients), were categorized as having a thin cornea (<500 µm) based on ultrasound pachymetry of central cornea thickness (CCT). To date, no eyes have developed ectasia, and the overall rate of postoperative complications is low in both the thin cornea group and thick cornea cohort of 79,534 eyes (41,230 patients) with a CCT ±500 µm, 1.19% versus 1.08%, respectively.
"The literature is mixed on the question of whether a thin cornea is an independent risk factor for ectasia," he said. "Several case-control studies [Tabbara KF, et al. Ophthalmology. 2006;113:1618-1622. Randleman JB, et al. Ophthalmology. 2008;115:37-50] have shown an association.
"However, the results from our analysis are consistent with several longitudinal studies [Caster AI, et al. J Refract Surg. 2007;23:782–788. Binder PS. J Cataract Refract Surg. 2007;33:1530–1538] that did not find a relationship between CCT and the development of ectasia in corneas with normal topography," he said. "It is important to note that ectasia can develop several years after LASIK. Because the follow-up is relatively short (12 to 24 months), our analysis is ongoing. We will continue to monitor these patients for many years to come."