Evaluation of corneal flattening in progressive keratoconus with Scheimpflug imaging

Abstract

Purpose: To evaluate characteristics of corneal flattening after cross-linking (CXL) therapy in progressive keratoconus with Scheimpflug imaging.

Methods: In this prospective study corneal CXL was performed in 23 progressive keratoconus eyes (CXL group) and 15 non-progressive keratoconus eyes served as controls (control group). Posterior elevation values (PE) were measured at the thinnest point of the cornea, at the corneal vertex, 2 and 3 mm paracentrally (superior, inferior, temporal and nasal from the corneal vertex) by fixed sphere reference surface with Scheimpflug-camera (Pentacam: Oculus Optikgeräte GmbH) before and 1 year after CXL. Student t-test on paired samples, and multivariable regression analysis using general estimating equation model were applied for statistical comparisons of corneal changes after CXL therapy.

Results: Thinnest corneal thickness and PE values measured at the thinnest point of the cornea decreased significantly in the CXL group (from 457.78±23.81µm to 432.52±30.29 μm, P<.001 and from 55.74±25.31 µm to 46.43±23.51 µm, P=.01, respectively). There was no statistically significant change in PE at the other corneal locations (P>.05) in the CXL group. All PE values remained stable in control eyes (P>.05). Change in PE values significantly correlated with initial ThCT in the CXL group (r=0.48 P=0.02). General estimating equation model also showed that CXL treatment significantly decreased PE only at the thinnest point of the cornea (with a mean 6.2 µm, P<.001) after adjustment for initial corneal thickness.

Conclusions: By describing the effect of corneal CXL therapy with changes in posterior elevation values, flattening could be detected only locally at the apex of the cone. The flattening effect of CXL treatment was more significant in thinner corneas.

Keywords: 574 keratoconus