Purpose: To assess the intraobserver and interobserver repeatability of curvature and aberrometric measurements of the posterior corneal surface provided by a Scheimpflug photography system in normal eyes.
Setting: Vissum-Instituto de Oftalmológico de Alicante, Alicante, Spain.
Methods: All eyes received a comprehensive ophthalmologic examination including corneal topographic analysis with a Scheimpflug photography system (Pentacam). Three repeated consecutive measurements were taken by 2 independent experienced examiners to assess intraobserver and interobserver repeatability for posterior corneal surface measurements. Keratometry, astigmatism, best-fit sphere (BFS), asphericity (Q), and aberrometry (6.0 mm pupil diameter) were analyzed. Precision, repeatability, and intraclass correlation coefficients were calculated for evaluating intraobserver repeatability. Bland-Altman analysis was used for assessing interobserver repeatability.
Results: Twenty eyes (20 patients) were included. Patients ranged in age from 21 to 50 years. The best intraobserver precision values were for BFS and Q in the central 8.0 mm (0.037 mm and 0.05, respectively). For both observers, intraobserver precision and repeatability achieved an acceptable level for keratometric readings (precision <0.09 diopter). The most limited intraobserver precision was for Q in the central 6.0 mm (0.117 observer 1; 0.099 observer 2). Interobserver ranges of agreement were not clinically relevant for any parameter except Q in the central 6.0 mm (0.116). Regarding aberrometry, intraobserver repeatability and interobserver repeatability were acceptable only for primary and secondary spherical aberration.
Conclusion: The Pentacam system provided reliable measurements of corneal posterior keratometry, astigmatism, and asphericity for large diameters of analysis. However, poor repeatability was observed for aberrometric measurements.