Comparison of corneal parameters in keratoconic subjects obtained from the pentacam and visante omni

Purpose: To compare corneal measurements including elevation, curvature and thickness values obtained using two imaging systems, a Scheimpflug camera (Pentacam) and an optical coherence tomography device (Visante OMNI) in keratoconic subjects. Methods: Corneal measurements from 35 eyes (22 subjects) were obtained using both devices and compared. Agreement was determined using the Bland- Altman analysis 95% limits of agreement (LoA). Results: The Pentacam measured significantly greater simulated keratometry readings in the flattest meridian (K1) (45.29 ± 3.48 diopters (D) versus 44.92 ± 2.97 D, p = 0.04) and in the steepest meridian (K2) (48.29 ± 3.83D versus 47.88 ± 3.49 D, p = 0.01). The Bland Altman 95% LoA between the devices were from −1.59 to 2.33 D for K1 and from −1.35 to 2.17 D for K2. Pentacam anterior corneal elevations were significantly higher (p = 0.03) as were posterior corneal elevations (p < 0.0001). The 95% LoA were from −15.59 to 24.51 μ and from −22.92 to 48.78 μ for anterior and posterior corneal elevations respectively. Compared to Visante OMNI, Pentacam recorded greater central corneal thickness (CCT) and minimum corneal pachymetry (MCP) values by 19.41 ± 18.25 μ and 13.03 ± 12.22 μ respectively (both p < 0.0001). The 95% LoA were from −16.37 to 55.19 μ for CCT and from −10.92 to 36.98 μ for MCP values. Conclusions: The Pentacam measured significantly greater corneal curvature, elevation and thickness values compared to Visante OMNI. In clinical practice, these devices are not interchangeable for corneal measurements in keratoconic subjects.