Steinwender Gernot, Kollenc Alexander, Shajari Mehdi, Sommer Michael, Borenich Andrea, Horwath-Winter Jutta, Lindner Ewald, Woltsche Nora, List Wolfgang, Wedrich Andreas
Department of Ophthalmology, Medical University Graz, Graz, Austria.
Department of Ophthalmology, Medical University Frankfurt, Frankfurt, Germany.
Front Med (Lausanne). 2022 Sep 20;9:968318. doi: 10.3389/fmed.2022.968318. eCollection 2022.
There exists remarkable variation in definitions for the location of the center of a keratoconus. The objective of this study was to analyze deviations between locations obtained by different tomographic maps for that purpose. Furthermore, it was investigated whether these deviations are influenced by disease severity.
In 162 eyes with keratoconus, corneal tomographic maps derived by Scheimpflug technology were retrospectively analyzed to determine the cone location with 5 different methods: maximum axial curvature of the front surface (Kmax), maximum tangential curvature of the front surface (tKmax), minimum pachymetry (Pachymin), maximum elevation of the front surface (ELEF), and maximum elevation of the back surface (ELEB). Distances between the locations were calculated and tested for a correlation with keratoconus severity and distance between cone and corneal vertex.
Cone locations derived from the curvature maps (Kmax, tKmax) showed the lowest agreement with the locations determined by pachymetry or elevation maps. The largest distances were found between Kmax and Pachymin [Median and Interquartile range: 1.19 mm (0.87, 1.60)], Kmax and ELEB [1.12 mm (0.79, 1.41)], and Kmax and ELEF [0.97 mm (0.64, 1.27)]. Low distances (<0.5 mm) were calculated between ELEB and ELEF, and ELEB and Pachymin. All of the calculated distances between the locations showed a significant negative correlation with keratoconus severity and most of them increased significantly with a more peripheral position of the cone ( < 0.05).
There was low consistency between different methods for describing the location of a keratoconus. Curvature-based determinations of the cone center (Kmax, tKmax) showed the highest deviations and should not be used for that purpose. However, the discrepancies between different cone location methods diminished with increasing disease severity and more central position of the cone.
圆锥角膜中心位置的定义存在显著差异。本研究的目的是分析为此目的通过不同断层图像获得的位置之间的偏差。此外，还研究了这些偏差是否受疾病严重程度的影响。
回顾性分析162例圆锥角膜患者的角膜断层图像，采用5种不同方法确定圆锥位置：前表面最大轴向曲率（Kmax）、前表面最大切向曲率（tKmax）、最小角膜厚度（Pachymin）、前表面最大高度（ELEF）和后表面最大高度（ELEB）。计算各位置之间的距离，并测试其与圆锥角膜严重程度以及圆锥与角膜顶点之间距离的相关性。
从曲率图（Kmax、tKmax）得出的圆锥位置与通过角膜厚度测量图或高度图确定的位置一致性最低。Kmax与Pachymin之间的距离最大[中位数和四分位间距：1.19 mm（0.87，1.60）]，Kmax与ELEB之间的距离为1.12 mm（0.79，1.41），Kmax与ELEF之间的距离为0.97 mm（0.64，1.27）。ELEB与ELEF之间以及ELEB与Pachymin之间的计算距离较短（<0.5 mm）。各位置之间计算出的所有距离均与圆锥角膜严重程度呈显著负相关，且其中大多数随着圆锥位置更偏向周边而显著增加（<0.05）。
描述圆锥角膜位置的不同方法之间一致性较低。基于曲率确定圆锥中心（Kmax、tKmax）显示出最大偏差，不应为此目的使用。然而，随着疾病严重程度增加和圆锥位置更靠近中心，不同圆锥位置方法之间的差异会减小。
