Introduction: Corneal thinning and changes in the corneal thickness profile are major symptoms of corneal ectasia. The anterior seg-ment optical coherence tomography is currently widely used, and the development of additional indices may lead to improvements in the diagnostics of keratoconus. Aim: To determine the diagnostic value of newly developed custom anterior segment OCT indices in diagnosing corneal ectasia. Patients and methods: Two sets of patients were included in the current study - healthy controls in the first and patients with corneal ectasia in the second, 80 eyes per group of 43 patients each. The groups were age- and sex-matched. Each patient underwent a standard ophthalmological examination (visual acuity, tonometry, slit lamp examination, fundus biomicroscopy), a corneal topography with OCULUS Keratograph 5M, and an anterior segment optical coherence tomography with RTVue-100. Besides the indices automatically generated by the software of the device, we measured the following custom parameters: partial corneal area (PCA), partial chamber area (PCA), and an index that reflects the relation between the two (CpC). All measurements were performed in two axial pachymetric scans, one vertical and one horizontal using the built-in software.&nbsp; Results: A statistically significant difference was found between the two groups (p<0.001, confidence Interval 95%) for all the proposed indices in both the vertical and the horizontal scans. The ROC analysis showed promising results for differentiation between the groups with the area under the curve (AUC) in the range from 0.892 for the vertical partial anterior chamber area to 0.984 for the vertical CpC index. Conclusions: The proposed indices can be used to differentiate between normal and ectatic corneas.

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