LASIK术后不同方法评价角膜屈光力的准确性分析

Accuracy analysis of evaluation of corneal refractive power with different methods after LASIK

目的分析LASIK术后角膜曲率计、角膜地形图及高斯光学公式评价角膜屈光力的准确性。方法以临床病史法计算所得的屈光源性K值为评价的基准,对LASIK术后44例(84只眼)角膜屈率计测得的K值、角膜地形图测得的有效屈光力值以及根据裂隙扫描角膜地形图(O rbscan)所测得的角膜前、后曲率半径,用高斯光学公式计算所得的角膜屈光力与之比较,并进行相关与回归分析。结果角膜率计测量的K值较病史法计算值低估(1.35±0.88)D(P<0.001),两者相关系数为0.885;EyeSys角膜地形图有效屈光力较病史法计算值低估(0.91±0.57)D(P<0.001),两者相关系数为0.964;差异均随角膜平面等效球镜度改变量的增加而增大;而高斯光学公式计算值所得较病史法计算值高估(0.31±0.34)D(P<0.001),与病史法计算值相关性最高(r=0.987)。结论以临床病史法计算值为基准,LASIK术后角膜屈率计和角膜地形图的测定值可通过角膜平面等效球镜度的改变量来矫正,在可获得角膜前、后曲率半径的情况下也可通过高斯公式而求得。

Objective To evaluate the accuracy of keratometry, computerized videokeratography and the gaussian optics formula for measuring corneal refractive power in patients after myopic laser in situ keratomieusis（LASIK）. Methods Eighty-four eyes of 44 patients who underwent LASIK were included in the study. Using the clinical history method as the standard（HisRP）, evaluated the accuracy of values of effective refractive power of the EyeSys corneal analysis（EffRP）, keratometry, the gaussian optics formula （GauRP） which took the radius of curvature cornea from orbscan. Results Post-operative EffRP and K values were higher than HisRP（1.35±0.88） D and （0.91±0.57） D respectively, and GauRP was lower than HisRP（0.31±0.34）D（P〈0.001 for all three comparison）. The correlation between GauRP and HisRP was the highest（r=0.987）. The differences between HisRP and both postoperative EffRP and K values increased significantly with the amount of myopic correction. Conclusion Using the clinical history method as the standard can raise the accuracy of computerized videokeratography and keratometry for measuring corneal refractive power in post-LASIK eyes by adjusting them according to the amount of LASIK-induced refraction change. It also can obtain the more accurate corneal refraction power in post-LASIK eyes by using the gaussian optics formula under, knowing the radius of curvature of anterior and posterior surface.