Effects of error in radius of curvature on the corneal power measurement before and after laser refractive surgery for myopia
Effects of error in radius of curvature on the corneal power measurement before and after laser refractive surgery for myopia
复制标题
近视激光屈光手术前后曲率半径误差对角膜屈光力测量的影响
DOI：
10.1111/j.1475-1313.2012.00921.x
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发表时间：
2012-07-01
影响因子：
2.9
通讯作者：
Zuo, Tong
中科院分区：
文献类型：
--
作者：
Liu, Yongji;Wang, Yan;Zuo, Tong
引文信息：刘毅，王毅，王正，左涛。近视眼激光屈光手术前后角膜曲率半径误差对角膜屈光力测量的影响。眼科生理学Opt 2012，32，355361。土井：10.1111/j.1475-1313.2012.00921.x摘要目的：探讨近视眼角膜屈光手术前后角膜屈光力测量的误差来源。方法：该研究包括28只眼睛，6名男性和8名女性，平均年龄为26岁（范围1839岁）。采用Pentacam旋转式Scheimpflug成像仪测量角膜前、后表面曲率半径、角膜前、后表面Q值和角膜中央厚度。分别计算3 mm环上顶点和旁中心区域的真实净屈光力Fg、后顶屈光力Fv和角膜曲率屈光力SimK。结果如下：对于处女眼，使用角膜曲率指数1.3375对角膜屈光力的高估（0.53 +/- 0.11 D）与曲率半径误差对角膜屈光力的低估（-0.21 +/- 0.09 D）相平衡，导致角膜屈光力误差相对较小，平均值为0.33 +/- 0.11 D。随着Q值从-0.09变化到-0.41，曲率半径误差平衡的百分比从16%增加到73%。然而，对于激光屈光手术后的眼睛，曲率半径误差导致高估（0.54 +/- 0.16 D）角膜屈光力，角膜曲率指数1.3375再次高估（1.59 +/- 0.26 D）角膜屈光力，导致平均值为2.12 +/- 0.40 D的较大测量误差。随着Q值从0.35变化到1.89，曲率半径误差增加的百分比从14%增加到32%。结论：对于处女眼，通过使用角膜曲率指数1.3375对角膜屈光力的高估被曲率半径误差对角膜屈光力的低估所平衡，导致相对较小的角膜屈光力误差。然而，对于激光屈光手术后的眼睛，更平坦的前角膜表面意味着使用1.3375的角膜曲率指数显著高估了角膜屈光力，并且曲率半径误差现在增加了这种高估并导致大的测量误差。
Citation information: Liu Y, Wang Y, Wang Z & Zuo T. Effects of error in radius of curvature on the corneal power measurement before and after laser refractive surgery for myopia. Ophthalmic Physiol Opt 2012, 32, 355361. doi: 10.1111/j.1475-1313.2012.00921.x Abstract Purpose: To investigate the sources of error in corneal power measurement before and after corneal refractive surgery for myopia. Methods: The study comprised 28 eyes of six males and eight females with a mean age of 26 (range 1839 years). The radius of curvature of anterior and posterior corneal surface, Q-Values of anterior and posterior corneal surface and corneal central thickness were measured by rotating Scheimpflug imaging (Pentacam). The true net power Fg, back vertex power Fv, and keratometric power SimK, were calculated respectively at the apex and at a paracentral area on the 3 mm ring. Results: For virgin eyes, the overestimation (0.53 +/- 0.11 D) of the corneal power by using a keratometric index of 1.3375 was balanced by the underestimation (-0.21 +/- 0.09 D) of the corneal power by the error in the radius of curvature, resulting in a relatively small corneal power error with a mean value of 0.33 +/- 0.11 D. With the Q-value changing from -0.09 to -0.41, the percentage balanced by the error in radius of curvature increased from 16% to 73%. However, for eyes after laser refractive surgery, the radius of curvature error lead to an overestimation (0.54 +/- 0.16 D) of the corneal power and the keratometric index of 1.3375 again overestimated (1.59 +/- 0.26 D) the corneal power, resulting in a large measurement error with a mean value of 2.12 +/- 0.40 D. With the Q-value changing from 0.35 to 1.89, the percentage added by the error in radius of curvature increased from 14% to 32%. Conclusions: For virgin eyes, the overestimation of the corneal power by using a keratometric index of 1.3375 is balanced by the underestimation of the corneal power by the error in the radius of curvature, resulting in a relatively small corneal power error. However, for eyes after laser refractive surgery, the flatter anterior corneal surface means that the use of a keratometric index of 1.3375 significantly overestimates the corneal power and the radius of curvature error now adds to this overestimation and results in a large measurement error.