The variability of corneal and anterior segment parameters in keratoconus

Purpose: To analyse, describe and test diverse corneal and anterior segment parameters in normal and keratoconic eyes to better understand the geometry of the keratoconic cornea. Method: 44 eyes from 44 keratoconic patients and 44 eyes from 44 healthy patients were included in the study. The Pentacam System was used for the analysis of the anterior segment parameters. New ad-hoc parameters were defined by measuring the distances on the Scheimpflug image at the horizontal diameter, with chamber depth now comprising of two distinctive distances: corneal sagittal depth and the distance from the endpoint of this segment to the anterior surface of the lens (DL). Results: Statistically significant differences (p < 0.05) between normal and keratoconic eyes were found in all of the analysed corneal parameters. Anterior chamber depth presented statistical differences between normal and keratoconic eyes (3.06 +/- 0.43 mm versus 3.34 +/- 0.45 mm, respectively; p = 0.004). This difference was found to originate in an increase of the DL distance (0.40 +/- 0.33 mm in normal eyes against 0.61 +/- 0.45 mm in keratoconic eyes; p = 0.014), rather than in the changes in corneal sagittal depth. Conclusion: These findings indicate that keratoconus results in central and peripheral corneal manifestations, as well as changes in the shape of the scleral limbus. The DL parameter was useful in describing the forward elongation and advance of the scieral tissue in keratoconic eyes. This finding may help in the monitoring of disease progression and contact lens design and fitting. (C) 2016 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.