Feizi Sepehr, Delfazayebaher Siamak, Ownagh Vahid, Sadeghpour Fatemeh
Ophthalmic Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
Ophthalmic Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
J Optom. 2018 Apr-Jun;11(2):113-120. doi: 10.1016/j.optom.2017.05.003. Epub 2017 Aug 4.
To evaluate the agreement between total corneal astigmatism calculated by vector summation of anterior and posterior corneal astigmatism (TCA) and total corneal astigmatism measured by ray tracing (TCA).
This study enrolled a total of 204 right eyes of 204 normal subjects. The eyes were measured using a Galilei double Scheimpflug analyzer. The measured parameters included simulated keratometric astigmatism using the keratometric index, anterior corneal astigmatism using the corneal refractive index, posterior corneal astigmatism, and TCA. TCA was derived by vector summation of the astigmatism on the anterior and posterior corneal surfaces. The magnitudes and axes of TCA and TCA were compared. The Pearson correlation coefficient and Bland-Altman plots were used to assess the relationship and agreement between TCA and TCA, respectively.
The mean TCA and TCA magnitudes were 0.76±0.57D and 1.00±0.78D, respectively (P<0.001). The mean axis orientations were 85.12±30.26° and 89.67±36.76°, respectively (P=0.02). Strong correlations were found between the TCA and TCA magnitudes (r=0.96, P<0.001). Moderate associations were observed between the TCA and TCA axes (r=0.75, P<0.001). Bland-Altman plots produced the 95% limits of agreement for the TCA and TCA magnitudes from -0.33 to 0.82D. The 95% limits of agreement between the TCA and TCA axes was -43.0 to 52.1°.
The magnitudes and axes of astigmatisms measured by the vector summation and ray tracing methods cannot be used interchangeably. There was a systematic error between the TCA and TCA magnitudes.
评估通过前后角膜散光矢量求和计算得到的总角膜散光（TCA）与通过光线追踪测量得到的总角膜散光（TCA）之间的一致性。
本研究纳入了204名正常受试者的204只右眼。使用Galilei双Scheimpflug分析仪对眼睛进行测量。测量参数包括使用角膜计指数的模拟角膜散光、使用角膜屈光指数的前角膜散光、后角膜散光和TCA。TCA通过前后角膜表面散光的矢量求和得出。比较TCA和TCA的大小和轴位。分别使用Pearson相关系数和Bland-Altman图来评估TCA和TCA之间的关系和一致性。
TCA和TCA的平均大小分别为0.76±0.57D和1.00±0.78D（P<0.001）。平均轴位方向分别为85.12±30.26°和89.67±36.76°（P=0.02）。TCA和TCA大小之间存在强相关性（r=0.96，P<0.001）。TCA和TCA轴位之间观察到中度相关性（r=0.75，P<0.001）。Bland-Altman图得出TCA和TCA大小的95%一致性界限为-0.33至0.82D。TCA和TCA轴位之间的95%一致性界限为-43.0至52.1°。
通过矢量求和和光线追踪方法测量的散光大小和轴位不能互换使用。TCA和TCA大小之间存在系统误差。
