Intraobserver and interobserver repeatability of curvature and aberrometric measurements of the posterior corneal surface in normal eyes using Scheimpflug photography

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.