To assess the Corvis ST (CST: Corneal Visualization Scheimpflug Technology) parameters change by progression of keratoconus and their ability for staging the disease.

84 keratoconic and 50 normal eyes were included. To assess the change of parameters by keratoconus severity, the keratoconus group were divided into two subgroups according to their TKC displayed by Pentacam and their corneal biomechanical parameters were measured by CST. The means of biomechanical parameters of two keratoconus subgroups and normal group were compared by ANOVA test.

The results showed that means of first applanation time (A1T), first applanation length (A1L), A1V (first applanation velocity), second applanation time (A2T), second applanation velocity (A2V), deformation amplitude (DA), and highest concavity radius (HCR) were significantly different among groups. There were no significant difference among groups for second applanation length (A2L), peak distance (PD), and highest concavity time (HCT). The results of Post hoc test revealed that the means of above mentioned parameters in normal group was different from two stages of keratoconus, but there were not significant mean differences between two keratoconus subgroups.

Values of most CST parameters were different between normal and keratoconus groups but none of the CST parameters were reliable index for keratoconus staging.