Shajari Mehdi, Friderich Stefan, Pour Sadeghian Miad, Schmack Ingo, Kohnen Thomas
Department of Ophthalmology, Goethe-University, Frankfurt am Main, Germany.
Cornea. 2017 Apr;36(4):457-462. doi: 10.1097/ICO.0000000000001143.
To evaluate and compare power and axis orientation of anterior and posterior astigmatism in eyes with keratoconus with healthy eyes.
In this retrospective cohort study, we examined 861 eyes of 494 patients diagnosed with keratoconus at the Department of Ophthalmology, University Hospital Frankfurt, and 256 eyes of 256 healthy individuals. Using a Scheimpflug device (Pentacam HR), we measured the magnitude and axis orientation of anterior and posterior corneal astigmatism, corneal thickness, and conus location. The results were compared between different stages of the disease according to the Amsler-Krumeich classification and the control group.
Magnitude of corneal astigmatism was 3.47 ± 2.10 diopters (D) on the anterior surface and 0.69 ± 0.40 D on the posterior surface in eyes across all keratoconus stages. We found a significant increase of anterior and posterior corneal astigmatism with progression of disease (P < 0.01, 1-way analysis of variance) and a significant correlation between anterior and posterior corneal astigmatism (r = 0.77, P < 0.01). In contrast to eyes of healthy individuals, in which posterior corneal axis alignment is vertical in most cases independent of anterior alignment, we found in eyes with keratoconus a match between anterior and posterior alignment when alignment was vertical in 97% of eyes, 46% when oblique and 61% when horizontal (Cohen kappa coefficient κ = 0.55, P < 0.01). With progression of disease, alignment of anterior and posterior corneal astigmatism became increasingly vertical.
In eyes with keratoconus, posterior axis alignment of corneal astigmatism is in line with alignment of the anterior surface in the majority of cases. Posterior astigmatism axis alignment could potentially be used in algorithms to support diagnosis and staging of keratoconus.
评估并比较圆锥角膜患者与健康人眼前后表面散光的度数及轴位方向。
在这项回顾性队列研究中，我们检查了法兰克福大学医院眼科诊断为圆锥角膜的494例患者的861只眼，以及256名健康个体的256只眼。使用眼前节分析系统（Pentacam HR）测量角膜前、后表面散光的度数和轴位方向、角膜厚度及圆锥位置。根据Amsler-Krumeich分类将疾病不同阶段的结果与对照组进行比较。
在所有圆锥角膜阶段的眼中，角膜前表面散光度数为3.47±2.10屈光度（D），后表面为0.69±0.40 D。我们发现随着疾病进展，角膜前、后表面散光显著增加（P<0.01，单因素方差分析），且角膜前、后表面散光之间存在显著相关性（r = 0.77，P<0.01）。与健康人眼不同，健康人眼大多数情况下角膜后表面轴位垂直，与前表面轴位无关，而在圆锥角膜患者中，当轴位垂直时，97%的眼前后表面轴位匹配；斜轴位时为46%；水平轴位时为61%（Cohen卡方系数κ = 0.55，P<0.01）。随着疾病进展，角膜前、后表面散光轴位越来越垂直。
在圆锥角膜患者中，大多数情况下角膜后表面散光轴位与前表面轴位一致。角膜后表面散光轴位有可能用于支持圆锥角膜诊断和分期的算法中。
