Clinical validation of point-source corneal topography in keratoplasty

Comparison of Color Light-Emitting Diode Corneal Topographer and Dual Rotating Scheimpflug-Placido Topographer

Purpose

To compare measurements of anterior and posterior keratometric values, using a color light-emitting diode corneal topographer and a dual rotating Scheimpflug-Placido topographer.

Methods

Anterior and posterior corneal index measurements were performed using a color light-emitting diode corneal topographer (Cassini) and a dual rotating Scheimpflug-Placido topographer (Galilei G4) and then compared. The paired t-test, intraclass correlation coefficients (ICCs), and Bland-Altman plots were used to evaluate the agreement between measurements.

Results

Sixty postrefractive surgery eyes and 60 normal eyes were evaluated. Both the color light-emitting diode corneal topographer and the dual rotating Scheimpflug-Placido topographer provided highly repeatable corneal measurements (ICC > 0.969). The agreement levels between the 2 devices for anterior corneal power, astigmatism magnitude, and J0 and J45 values were ICC > 0.906 for the total group. However, the ICC values for posterior corneal power, astigmatism magnitude, and J0 and J45 values were lower than 0.681 for the total group.

Conclusions

The anterior keratometric values obtained by the color light-emitting diode corneal topographer and the dual rotating Scheimpflug-Placido topographer showed high agreement levels, but the posterior keratometric values showed lower agreement levels.

Evaluation of keratometry with a novel Color-LED corneal topographer

PURPOSE

To assess the performance of a novel keratometer based on reflections of colored light-emitting diodes (LEDs) and compare it with devices based on Placido rings, monochromatic LEDs, and Scheimpflug images.

METHODS

Sixty-three eyes of 63 patients with virgin corneas underwent keratometry with color-LED corneal topography (Cassini; i-Optics, The Hague, The Netherlands) and with devices based on Placido ring reflections (Keratron; Optikon, Rome, Italy), monochromatic LED reflections (Lenstar; Haag-Streit, Koeniz, Switzerland), and Scheimpflug imaging (Pentacam; Oculus Optikgeräte, Wetzlar, Germany). Three repeated measurements were performed with each device. Comparability and repeatability of corneal power and cylinder measurements were assessed. The Bonferroni-corrected α-threshold for statistical significance was 0.016.

RESULTS

Corneal power measurements with the Cassini topographer were not statistically significantly different from those with the Pentacam (P = .64). They were statistically significantly lower than those with the Keratron and Lenstar (P < .01), but the differences were of negligible clinical relevance. Cylinder measurements with the Cassini topographer were not statistically significantly different from those with any other device (P = .46). Repeatability of Cassini corneal power measurements was not statistically significantly different from that of the Keratron (P = .02), but was statistically significantly lower than that of the Lenstar and Pentacam (P < .001). Repeatability of Cassini cylinder measurements was statistically significantly higher than that of the Pentacam and Keratron (P < .001), but was not statistically significantly different from that of the Lenstar (P > .05).

CONCLUSIONS

Corneal power and cylinder measurements with color-LED corneal topography yielded values that were comparable to those of other commonly used devices. Repeatability of corneal power measurements was lower compared to some devices, but repeatability of cylinder measurements was relatively high. This may be of particular interest when using toric intraocular lenses.