Stakheev A A, Balashevich L J
Cornea. 2003 Apr;22(3):214-20. doi: 10.1097/00003226-200304000-00006.
To assess the accuracy of different corneal power determination methods in patients who had undergone myopic laser in situ keratomileusis (LASIK), photorefractive keratectomy (PRK), and radial keratotomy (RK).
The results for 208 eyes of 116 patients who had had corneal refractive surgery (LASIK, PRK, RK) for myopia were analyzed retrospectively. Keratometry measurements, i.e., autokeratometry readings (K(meas)), simulated keratotopography readings (Sim-K), and topographically measured average central corneal power in a 3-mm zone (ACP) were compared with calculated refraction-derived keratometric value. Correction factors based on the difference between measured and calculated keratometric powers were rated.
Direct power measurements with standard keratometers and planokeratotopography systems overestimate corneal power after myopic PRK and LASIK. The average K(meas) and K(topo) were significantly greater than the average calculated refraction-derived keratometric values. Corneal power overestimation correlated significantly with the spherical equivalent change after refractive surgery (p < 0.001). After RK, there is no significant correlation of the difference between all measured K values and refraction-derived power with the spherical equivalent change. In these cases, the Sim-K value seems the most accurate among measured keratometric powers. The precision of measurement significantly depends on the parameters of the autokeratometer (i.e., measurement place, number of measurement points, keratometric index of refraction).
To avoid underestimation of intraocular lens power after cataract surgery in the eyes that had previously undergone myopic corneal refractive surgery, the measured corneal power must be corrected. Although correction factors may be calculated for cases after PRK and LASIK, there are no universal and absolutely reliable methods to determine corneal power in these cases. More than one accessible method should be used, and the lowest, most reliable data should be used.
评估不同角膜屈光力测定方法在接受近视性准分子原位角膜磨镶术（LASIK）、准分子激光角膜切削术（PRK）和放射状角膜切开术（RK）患者中的准确性。
回顾性分析116例因近视接受角膜屈光手术（LASIK、PRK、RK）的208只眼的结果。将角膜曲率测量结果，即自动角膜曲率计读数（K(meas)）、模拟角膜地形图读数（Sim-K）以及3毫米区域内的地形图测量平均中央角膜屈光力（ACP）与计算得出的验光衍生角膜曲率值进行比较。根据测量的和计算的角膜屈光力之间的差异对校正因子进行评级。
使用标准角膜曲率计和平面角膜地形图系统进行的直接屈光力测量在近视PRK和LASIK术后高估了角膜屈光力。平均K(meas)和K(topo)显著大于平均计算得出的验光衍生角膜曲率值。角膜屈光力高估与屈光手术后等效球镜度变化显著相关（p < 0.001）。RK术后，所有测量的K值与验光衍生屈光力之间的差异与等效球镜度变化无显著相关性。在这些情况下，Sim-K值在测量的角膜曲率屈光力中似乎最准确。测量精度显著取决于自动角膜曲率计的参数（即测量位置、测量点数、角膜曲率测量折射率）。
为避免在先前接受近视性角膜屈光手术的眼中白内障手术后人工晶状体屈光力估计不足，必须对测量的角膜屈光力进行校正。虽然可以为PRK和LASIK术后的病例计算校正因子，但在这些情况下没有通用且绝对可靠的方法来确定角膜屈光力。应使用一种以上可行的方法，并采用最低、最可靠的数据。
