Comparison of corneal curvature parameters obtained from two different instruments-Pentacam and VX120

To explore whether the same corneal curvature parameters and anterior chamber depth measured by Pentacam and VX120 have a good consistency and can replace each other.

This study enrolled 140 eyes of 70 patients ranging in age from 19 to 53y. All eyes underwent a comprehensive ophthalmologic examination including an anterior segment analysis with the VX120 system (Visionix-Luneau Technologies, Chartres, France) and Pentacam (Oculus Optikgerate GmbH) respectively. The comparison on corneal curvature parameters was done between Pentacam and VX120 using clustered signed rank test; the interclass correlation coefficients (ICC) with 95% confidence intervals (CI) was calculated for each parameter between Pentacam and VX120; the Bland-Altman plot of each parameter was supplemented.

The anterior corneal curvature measured by VX120 was Ks: 44.00±1.78 D, KsAt: 89.45±22.18, Kf: 42.84±1.58 D, KfAt: 93.91±79.34; which measured by Pentacam was Ks: 43.80±1.82 D, KsAt: 91.17±21.40, Kf: 42.61±1.64 D, KfAt: 91.16±78.69. There was statistical difference between Pentacam and VX120 for anterior corneal curvature parameter (P<0.001). The posterior corneal curvature measured by VX120 was Ks: -6.42±1.23 D, KsAt: 91.00±23.45, Kf: -5.85±1.24 D, KfAt: 95.93±79.11; which measured by Pentacam was Ks: -6.44±0.32 D, KsAt: 92.24±11.75, Kf: -6.01±1.05 D, KfAt: 74.43±80.64. There was statistical difference between Pentacam and VX120 for posterior corneal curvature parameters (P<0.001). Anterior chamber depth (ACD) measured by Pentacam and VX120 was statistically different. Pentacam and VX120 achieved high consistency only on corneal anterior surface, including Ks and Kf. The ICCs were 0.96 (95%CI: 0.95, 0.97) and 0.95 (95%CI: 0.94, 0.97) respectively. For other corneal surface curvature parameters, all ICCs of between Pentacam and VX120 were below 0.87. Bland-Altman plots indicated of low consistency of corneal surface curvature parameters measured by Pentacam and VX120.

The corneal curvature parameters and anterior chamber depth measured by Pentacam and VX120 were statistically different. Data measured by Pentacam and VX120 is not suggested to replace each other, mixing data measured by Pentacam and VX120 together is not suggested either.