Characteristic of entire corneal topography and tomography for the detection of sub-clinical keratoconus with Zernike polynomials using Pentacam

Zhe Xu, Weibo Li, Jun Jiang, Xiran Zhuang, Wei Chen, Mei Peng, Jianhua Wang, Fan Lu, Meixiao Shen, Yuanyuan Wang, Zhe Xu, Weibo Li, Jun Jiang, Xiran Zhuang, Wei Chen, Mei Peng, Jianhua Wang, Fan Lu, Meixiao Shen, Yuanyuan Wang

Abstract

The study aimed to characterize the entire corneal topography and tomography for the detection of sub-clinical keratoconus (KC) with a Zernike application method. Normal subjects (n = 147; 147 eyes), sub-clinical KC patients (n = 77; 77 eyes), and KC patients (n = 139; 139 eyes) were imaged with the Pentacam HR system. The entire corneal data of pachymetry and elevation of both the anterior and posterior surfaces were exported from the Pentacam HR software. Zernike polynomials fitting was used to quantify the 3D distribution of the corneal thickness and surface elevation. The root mean square (RMS) values for each order and the total high-order irregularity were calculated. Multimeric discriminant functions combined with individual indices were built using linear step discriminant analysis. Receiver operating characteristic curves determined the diagnostic accuracy (area under the curve, AUC). The 3rd-order RMS of the posterior surface (AUC: 0.928) obtained the highest discriminating capability in sub-clinical KC eyes. The multimeric function, which consisted of the Zernike fitting indices of corneal posterior elevation, showed the highest discriminant ability (AUC: 0.951). Indices generated from the elevation of posterior surface and thickness measurements over the entire cornea using the Zernike method based on the Pentacam HR system were able to identify very early KC.

Conflict of interest statement

The authors declare that they have no competing interests.

Figures

Figure 1
Figure 1
Receiver operating characteristic (ROC) curves of discriminant functions for normal, sub-clinical KC, and KC groups. (A) ROC curve of the output value of discriminant functions for sub-clinical KC group versus normal group. (B) ROC curve of the output value of discriminant functions for KC group versus sub-clinical KC group.

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