From the Rothschild Foundation (Saad, Gatinel) and the Center of Expertise and Research in Optics for Clinicians (Saad, Gatinel), Paris, France; American University of Beirut (Saad), Beirut, Lebanon; Gavin Herbert Eye Institute (Binder), Department of Ophthalmology, University of California Irvine, Irvine, California, USA.
From the Rothschild Foundation (Saad, Gatinel) and the Center of Expertise and Research in Optics for Clinicians (Saad, Gatinel), Paris, France; American University of Beirut (Saad), Beirut, Lebanon; Gavin Herbert Eye Institute (Binder), Department of Ophthalmology, University of California Irvine, Irvine, California, USA.
J Cataract Refract Surg. 2017 Jul;43(7):946-951. doi: 10.1016/j.jcrs.2017.04.040.
To assess the currently recommended percentage tissue altered (PTA) metric for its ability to screen for ectasia after laser in situ keratomileusis (LASIK).
Gavin Herbert Eye Institute, University of California, Irvine, California, USA, and Rothschild Foundation, Paris, France.
Retrospective case series.
The study used a LASIK database created by 1 surgeon for LASIK cases with normal preoperative topography that had a minimum follow-up of 24 months with complete preoperative and intraoperative data to permit the calculation of PTA values to detect eyes at risk for developing ectasia.
Of the eyes, 593 eyes had complete data and met the inclusion criteria. Based on measured flap thickness, 126 eyes (21%) had a PTA value of 40% or more (mean 44) and a percentage of that flap thickness accounted for the PTA (mean 66.7%; range 34% to 92%). The mean attempted laser ablation was 79.8 μm ± 29.2 (SD), and the mean residual bed thickness was 304.4 ± 29.2 μm (range 212 to 369 μm). No eye developed ectasia over a mean follow-up of 30 months.
The current PTA calculation when applied to a LASIK population with normal preoperative topography and flap thickness measured with ultrasound did not predict the risk for ectasia. Differences between study populations and assumptions might have accounted for the different outcomes obtained in the initially published PTA study.
评估目前推荐的组织改变百分比（PTA）指标，以筛查激光原位角膜磨镶术（LASIK）后是否发生扩张。
美国加利福尼亚大学欧文分校加文赫伯特眼科研究所和法国巴黎罗斯柴尔德基金会。
回顾性病例系列。
该研究使用了一位外科医生创建的 LASIK 数据库，该数据库用于术前 topography 正常的 LASIK 病例，随访时间至少为 24 个月，并且具有完整的术前和术中数据，以计算 PTA 值来检测有发生扩张风险的眼睛。
在符合纳入标准的 593 只眼中，有 126 只眼（21%）的 PTA 值为 40%或更高（平均为 44%），且 flap thickness 的百分比占 PTA（平均为 66.7%；范围为 34%至 92%）。平均尝试的激光消融量为 79.8μm±29.2（SD），平均剩余床厚度为 304.4μm±29.2μm（范围为 212μm 至 369μm）。在平均 30 个月的随访中，没有一只眼睛发生扩张。
目前的 PTA 计算应用于术前 topography 正常且 flap thickness 用超声测量的 LASIK 人群中，并不能预测扩张的风险。研究人群和假设的差异可能导致最初发表的 PTA 研究中得出不同的结果。
