Comparison and correlation between anterior and posterior elevation maps in normal and keratoconus patients

Abstract

Background:Keratoconus (KC) is a progressive disorder with conical deformity of the cornea. It is characterized by corneal thinning induces irregular astigmatism, myopia and protrusion resulting in mild to marked impairment in the quality of vision. Aim of work : Measuring posterior corneal elevation in normal and keratoconus corneas using pentacam to discriminate keratoconus from normal corneas and to compare and correlate anterior corneal elevation maps and posterior corneal elevation maps with severity of keratoconus. Methods: This study included 50 participants, 25 KC patients and 25 healthy subjects. All cases were submitted to evaluation in the form of: history taking, visual acuity testing (UCVA, BCVA), slit lamp examination, corneal topography. Results: The comparison of keratometric and pachymetric readings showed significant differences between the study and control groups, central astigmatism (frontal and back), Kmax, KI, ISV and IVA show statistically significant difference between normal and keratoconic eyes. Posterior surface of the cornea shows statistically significant difference between normal and keratoconic eyes, In all keratoconus stages, the Posterior corneal elevation was significantly higher than the anterior corneal elevation by increasing in the keratoconus severity. Conclusion: Our data support the hypothesis that the posterior corneal surface contributes to the early topographical manifestation of keratoconus in keratoconus eyes. Although the diagnostic sensitivity was not explicitly evaluated in our study, giving more attention to posterior surface parameters may facilitate the early detection of keratoconus corneas.