PURPOSE

To investigate the diagnostic capability of Fourier indices in detecting clinical or subclinical keratoconus (KC).

DESIGN

Prospective cross-sectional study.

METHODS

The study included 126 eyes with clinical KC (50 KC without any corneal scar, 50 KC with anterior corneal scar, and 26 KC with posterior scar having a history of acute corneal hydrops), 50 with topographic KC (without clinical signs), 50 with pre-topographic KC (normal topography without clinical signs), and 50 controls.

Corneal tomographic data were obtained using anterior segment optical coherence tomography (OCT). Fourier analysis decomposed dioptric data from both anterior and posterior corneal surface into spherical, regular astigmatism, asymmetry, and higher-order irregularity components. The discriminating ability of the Fourier indices of pre-topographic KC, topographic KC, and clinical KC from controls were assessed after quantitative Fourier analysis of irregular corneal astigmatism.

RESULTS

Posterior asymmetry and higher-order irregularity components were significantly greater in pre-topographic KC eyes than those in controls (P < .001 for both), with the highest area under the receiver operating characteristic curve (AUROC) of 0.778 and 0.709, respectively. The same was true for anterior asymmetry, posterior asymmetry, and posterior higher-order irregularity components in topographic KC (AUROC of 0.945, 0.941, and 0.893, respectively), whereas it was >0.948 for all Fourier components in clinical KC.

CONCLUSIONS

Fourier analysis using OCT can evaluate anterior and posterior corneal irregular astigmatism of various KC stages, from very mild to advanced, including severe cases with corneal scar. Irregular astigmatism indices from the posterior corneal surface showed the highest AUROC values in discriminating early KC stages.

中文翻译：

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光学相干断层扫描对圆锥角膜不同严重程度不规则角膜散光的傅立叶分析

目的

研究傅立叶指数在检测临床或亚临床圆锥角膜 (KC) 中的诊断能力。

设计

前瞻性横断面研究。

方法

该研究包括 126 只患有临床 KC 的眼睛（50 只 KC 没有任何角膜瘢痕，50 只 KC 有前角膜瘢痕，26 只 KC 有后部瘢痕，有急性角膜水肿病史），50 只有地形图 KC（无临床体征），50 只有预地形图 KC（无临床体征的正常地形图）和 50 个对照。

使用眼前节光学相干断层扫描 (OCT) 获得角膜断层扫描数据。傅立叶分析将前后角膜表面的屈光度数据分解为球面、规则散光、不对称和高阶不规则成分。在对不规则角膜散光进行定量傅里叶分析后，评估了前地形 KC、地形 KC 和临床 KC 的傅里叶指数与对照的鉴别能力。

结果

前地形图 KC 眼的后部不对称和高阶不规则成分明显大于对照组（两者P < .001），接受者操作特征曲线 (AUROC) 下的最高面积分别为 0.778 和 0.709。地形 KC 中的前不对称、后不对称和后高阶不规则分量也是如此（AUROC 分别为 0.945、0.941 和 0.893），而临床 KC 中的所有傅立叶分量均 > 0.948。

结论

使用 OCT 的傅立叶分析可以评估各种 KC 阶段的前后角膜不规则散光，从非常轻微到晚期，包括角膜瘢痕的严重病例。来自角膜后表面的不规则散光指数在区分早期 KC 阶段时显示出最高的 AUROC 值。