准分子激光角膜原位磨镶术后角膜曲率计算方法的研究

Calculation of corneal curvature after laser in situ keratomileusis for correction of myopia

目的探讨准分子激光原位角膜磨镶术（LASIK）后角膜曲率的计算方法，以得到LASIK术后准确的角膜曲率。方法应用临床资料进行LASIK后角膜曲率计算公式的推导，并应用临床加以验证。对临床上127例（242只眼）行LASIK的患者进行回顾性分析。通过患者手术前后的等效球镜度数和角膜曲率，计算出其角膜平面球镜度数和LASIK后角膜平面球镜度数改变量。将观察的患者随机分为两组，用第一组患者的资料推导出两个不同的角膜曲率计算公式，即回归法计算公式和屈光度数依赖法计算公式，之后用第二组患者的资料来验证公式，用推导出的公式计算所得的角膜曲率值与临床病史法所得的角膜曲率值进行对比。结果用回归法计算公式所得K回归=-5．657＋1．115Kpost，用屈光度依赖法所得K屈光度数依赣=Kpost-（0．24·ASEQco）。两种方法计算出的角膜曲率与现在临床常用的临床病史法所计算的角膜曲率有高度的相关性（r=0．955，0．928；P〈0．01），各公式计算的K值之间的差异无统计学意义（P〈0．05）。结论回归法计算公式和屈光度数依赖法计算公式均可靠。当术前相关资料无法完整提供时可用回归法计算公式和屈光度数依赖法计算公式对术后角膜曲率进行校正。

Objective To describe and evaluate a refraction-derived method and a clinical-derived method to calculate the correct corneal curvature for intraocular lens （IOL） power calculations after laser in situ keratomileusis （LASIK） and to compare the results to the commonly used history-derived method. Method Retrospective analysis of consecutive case treated with LAIK clinically. We measured pre-LASIK and post-LASIK spectacle refraction, pre-LASIK and post-LASIK K readings in each patient. We then calculated pre- and post-LASIK refraction at the corneal plane and the amount of correction obtained by the refraction surgery. Patients were divided into two groups. Group I was used to establish the two different formulas for the refraction- and clinical-derived methods. The values obtained with these two methods were compared with the K by history-derived method （Kc. hd） in group Ⅱ to validate the results. Results The K values calculated using the refraction-derived method and clinical-derived method were correlated significantly with that obtained from Kc. hd. Conclusion The calculation of corneal curvature for intraocular lens （IOL） power calculation after LASIK can use the refraction- and clinical-derived methods instead of history-derived method when some refractive parameters are not available.