角膜后表面散光的测量及临床意义

角膜散光由角膜前表面散光（anterior astigmatism，AA）和角膜后表面散光（posterior astigmatism，PA）组成。据文献统计，PA在-0.01~-1.10 D范围内，85.0%~96.1%为逆规散光。随着年龄的增长，PA总体呈现由逆规向顺规漂移的趋势，AA的趋势则与之相反。因此，对于青年人，PA使总角膜散光（total astigmatism，TA）减小；对于老年人，PA使TA增大。在临床上，忽略PA会错误估计TA，影响屈光性白内障手术后的视觉质量。本文旨在介绍PA的测量方法及临床意义，以供眼科医生在临床工作中参考。

Measurement and clinical significant of posterior corneal astigmatism

Corneal astigmatism includes anterior astigmatism (AA) and posterior astigmatism (PA).According to the literature，85.0%-96.1% PA ranging from -0.01 to -1.10 D refers to astigmatism against the rule.With the age increasing，PA shows a significant trend from astigmatism against the rule to with the rule，while AA shows toward against-the-rule astigmatism.Therefore，PA often leads to partially decrease of total astigmatism (TA) in young adults，but the increase of TA in aged elderly.Clinically，ignorance of PA will lead to a false estimate of TA，thereby affecting visual quality after refractive cataract surgery.And this article aims to introduce the measurement of PA and its clinical significance for providing the reference in clinical practices.