Comparison of Corneal Thickness Progression from Center to Periphery in Keratoconus, Keratoconus Suspected and Normal Corneas

To compare the corneal thickness progression (CTP) and progression index (PI) in keratoconus (KCN), keratoconus suspected (KS) and normal corneas, using Scheimpflug photography (Pentacam). Three-hundred eyes were evaluated using rotating Scheimpflug photography (Pentacam). On the basis of anterior sagital curvature, maximum posterior elevation (MPE) and thinnest point of pachimetry (TP) the eyes were divided into three equal groups. The normal group had normal anterior topography, pachimetry 500µ or more and MPE less than 20µ, KS group had a suspected topography and KCN group had definit topographic findings. The eyes were evaluated by "pachimetric map", "Corneal thickness spatial profile" and "percentage of corneal thickness" and mean of "progression Index" calculated for each eye and data analysis was performed with SPSS software. Mean MPE was 13.203.95 µ in the normal group, 19.806.75 µ in the KS group and 40.9316.21 in the KCN group. Mean TP was 541.5327.92 µ in the normal group, 504.1531 µ in the KS group and 461.0946.84 µ in the KCN group. Mean PI was 0.910.15 in the normal group, 1.110.20 in the KS group and 2.000.73 in the KCN group. This study demonstrated that, all of three parameters (MPE, TP and PI) had statistically significant difference between three groups (P<0.001). A statistically significant but week correlation was found between PI and the severity of keratoconus. In addition to topography, central corneal thickness, posterior and anterior elevation, PI and CTP can be used to distinglish normal corneas from KS and KCN ones.