Evaluation of the percentage tissue altered as a risk factor for developing post-laser in situ keratomileusis ectasia.

摘要: Purpose To assess the currently recommended percentage tissue altered (PTA) metric for its ability to screen ectasia after laser in situ keratomileusis (LASIK). Setting Gavin Herbert Eye Institute, University of California, Irvine, USA, and Rothschild Foundation, Paris, France. Design Retrospective case series. Methods The study used a LASIK database created by 1 surgeon cases with normal preoperative topography that had a minimum follow-up 24 months complete intraoperative data permit calculation PTA values detect eyes at risk developing ectasia. Results Of eyes, 593 met the inclusion criteria. Based on measured flap thickness, 126 (21%) value 40% or more (mean 44) thickness accounted 66.7%; range 34% 92%). mean attempted laser ablation was 79.8 μm ± 29.2 (SD), residual bed 304.4 ± 29.2 μm (range 212 369 μm). No eye developed over of 30 months. Conclusions current when applied LASIK population ultrasound did not predict ectasia. Differences between populations assumptions might have different outcomes obtained the initially published study.