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Abstract Keratoconus is a non-inflammatory progressive bilateral ectatic corneal disorder. clinically manifestations are characterized by decreased visual acuity due to irregular astigmatism secondary to progressive anterior protrusion, apical thinning, and corneal scarring in advanced cases. Its incidence is estimated to be approximately 1 per 2000 in the general population. Detection of this disease is particularly important among candidates prepared for refractive surgery, in whom the prevalence of keratoconus and subclinical keratoconus has been reported to be greater than in the normal population.There was a dramatic change in the diagnosis and early identification of keratoconus and other ectatic disorders. Imaging techniques have played a large part in this change. Scheimpflug imaging is considered among the most prevalent modalities in the diagnosis, staging, and follow-up of patients with Keratoconus. Pentacam allows for measuring local elevation points by fitting the corneal shape to a best-fit sphere (BFS) reference surface with variable diameters or to a best-fit toric ellipsoid surface (BFTE), which simulates more the corneal shape than the BFS. This study was performed with aim of detecting the changes in corneal elevation values for both anterior and posterior corneal surfaces using different acquisition diameters (8, 9 mm) with reference surfaces BFS and BFTE in both normal population and keratoconus patients. Statistical analyses revealed that sensitivity and specificity of the analyzed topographic parameters were higher in keratoconus corneas (group B) than in normal corneas (group A) (p<0.001). The AUROC analyses showed high overall predictive accuracy of anterior elevation and posterior elevation for KC (AUROC 0.99 for 8mm BFS with sensitivity and specificity 96%). |