Dual versus single Scheimpflug camera for anterior segment analysis: Precision and agreement.

PURPOSE: To assess the repeatability, reproducibility, and agreement of the Pentacam HR single-camera and Galilei G2 dual-camera Scheimpflug devices in anterior segment analysis.

SETTING

Begitek Clínica Oftalmológica, San Sebastián, Spain.

DESIGN

Prospective randomized observational study.

METHODS

Healthy young individuals had 3 consecutive tests by 2 examiners. Analyzed parameters were anterior and posterior cornea simulated keratometry (K), K flat, K steep, astigmatism magnitude and axis, J(0) and J(45) vectors, asphericity, total corneal higher-order wavefront aberrations (root mean square [RMS], coma, trefoil, spherical aberration), central cornea and thinnest-point thicknesses, and anterior chamber depth. Repeatability and reproducibility were evaluated by calculating the within-subject standard deviation (S(w)), some derived coefficients, and the intraclass correlation coefficient. Agreement was assessed with the Bland-Altman method.

RESULTS

The single-camera device reproducibility (S(w)) was simulated K, 0.04 diopter (D); J(0), 0.03 D; J(45), 0.04 D; total power, 0.04 D; spherical aberration, 0.02 μm; higher-order aberrations (HOAs), 0.02 μm; central corneal thickness (CCT), 3.39 μm. The dual-camera device S(w) was simulated K, 0.07 D; J(0), 0.13 D; J(45), 0.04 D; total power, 0.08 D; spherical aberration, 0.02 μm; HOAs, 0.11 μm; CCT, 1.36 μm. Agreement was good for most parameters except total corneal power (mean difference 1.58 D ± 0.22 (SD) and HOA RMS (mean difference 0.48 ± 0.19 μm) (both P<.00).

CONCLUSIONS

Repeatability and reproducibility were good for all parameters. The single-camera device was more precise for curvature, astigmatism, and corneal wavefront error measurements and the dual-camera device for pachymetry measurements. Agreement was good with some relevant exceptions.

FINANCIAL DISCLOSURE: Dr. Aramberri is consultant to Costruzione Strumenti Oftalmici, Firenze, Italy. No other author has a financial or proprietary interest in any material or method mentioned.