Cullen Eye Institute, Department of Ophthalmology, Baylor College of Medicine, Houston, Texas 77030, USA.
J Cataract Refract Surg. 2012 Dec;38(12):2080-7. doi: 10.1016/j.jcrs.2012.08.036. Epub 2012 Oct 12.
To determine the contribution of posterior corneal astigmatism to total corneal astigmatism and the error in estimating total corneal astigmatism from anterior corneal measurements only using a dual-Scheimpflug analyzer.
Cullen Eye Institute, Baylor College of Medicine, Houston, Texas, USA.
Case series.
Total corneal astigmatism was calculated using ray tracing, corneal astigmatism from simulated keratometry, anterior corneal astigmatism, and posterior corneal astigmatism, and the changes with age were analyzed. Vector analysis was used to assess the error produced by estimating total corneal astigmatism from anterior corneal measurements only.
The study analyzed 715 corneas of 435 consecutive patients. The mean magnitude of posterior corneal astigmatism was -0.30 diopter (D). The steep corneal meridian was aligned vertically (60 to 120 degrees) in 51.9% of eyes for the anterior surface and in 86.6% for the posterior surface. With increasing age, the steep anterior corneal meridian tended to change from vertical to horizontal, while the steep posterior corneal meridian did not change. The magnitudes of anterior and posterior corneal astigmatism were correlated when the steeper anterior meridian was aligned vertically but not when it was aligned horizontally. Anterior corneal measurements underestimated total corneal astigmatism by 0.22 @ 180 and exceeded 0.50 D in 5% of eyes.
Ignoring posterior corneal astigmatism may yield incorrect estimation of total corneal astigmatism. Selecting toric intraocular lenses based on anterior corneal measurements could lead to overcorrection in eyes that have with-the-rule astigmatism and undercorrection in eyes that have against-the-rule astigmatism.
The authors received research support from Ziemer Group. In addition, Dr. Koch has a financial interest with Alcon Laboratories, Inc., Abbott Medical Optics, Inc., Calhoun Vision, Inc., NuLens, and Optimedica Corp.
确定后角膜散光对总角膜散光的贡献，以及仅使用双 Scheimpflug 分析仪从前角膜测量值估计总角膜散光的误差。
美国得克萨斯州休斯顿贝勒医学院 Cullen 眼科研究所。
病例系列。
使用光线追踪法计算总角膜散光、模拟角膜曲率计的角膜散光、前角膜散光和后角膜散光，并分析其随年龄的变化。使用向量分析评估仅从前角膜测量值估计总角膜散光产生的误差。
本研究共分析了 435 例连续患者的 715 只眼。后角膜散光的平均大小为 -0.30 屈光度（D）。前表面 51.9%的眼和后表面 86.6%的眼陡峭角膜子午线垂直（60 至 120 度）排列。随着年龄的增长，前角膜陡峭子午线倾向于从垂直变为水平，而后角膜陡峭子午线则没有变化。当较陡的前子午线垂直排列时，前、后角膜散光的大小具有相关性，但当它水平排列时则没有相关性。忽略后角膜散光可能会导致总角膜散光的估计不准确。根据前角膜测量值选择 toric 人工晶状体可能会导致规则性散光眼过度矫正，而逆规性散光眼矫正不足。
忽略后角膜散光可能会导致总角膜散光的估计不准确。根据前角膜测量值选择 toric 人工晶状体可能会导致规则性散光眼过度矫正，而逆规性散光眼矫正不足。
作者得到了 Ziemer 集团的研究支持。此外，Koch 博士与 Alcon Laboratories, Inc.、Abbott Medical Optics, Inc.、Calhoun Vision, Inc.、NuLens 和 Optimedica Corp. 有财务利益关系。
