الفهرس 
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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%).