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Reliability of anterior curvature measurements using the rotating Scheimpflug camera and placido-disk topography in keratoconic and post-LASIK corneas

Poster Details

First Author: R.Penna ITALY

Co Author(s):    M. Catalano   U. de Sanctis   L. Brusasco   F. Grignolo     

Abstract Details



Purpose:

To compare reproducibility and repeatability of rotating Scheimpflug camera (Pentacam HR, Oculus, Wetzlar, Germany) and Placido disk - based topography (CSO Eyetop, Costruzione Strumenti Oftalmici, Florence, Italy) in measuring anterior curvature in keratoconic and post-LASIK corneas.

Setting:

Department of Surgical Sciences. Ophthalmology Institute. University of Turin, Italy.

Methods:

Steep keratometry (Ks), flat keratometry (Kf), mean keratometry (Km) and Ks-Kf difference of the anterior cornea were measured in a single session by two examiners using both instruments, on one eye of 36 keratoconic and 20 post-LASIK patients. In the same session, all measurements were then repeated by examiner 1 (M.C.). Reproducibility and repeatability of measurements made with the two instruments were assessed by calculating the intraclass correlation coefficient (ICC) and the Bland-Altman coefficient of repeatability (CoR).

Results:

In keratoconic corneas, the rotating Scheimpflug camera measured Ks and Kf more reproducibly and more repeatably than Placido disk-based topography. CoR between examiners was respectively 0.59 vs. 0.92 diopters (D) for Ks, and 0.35 vs. 0.95 D for Kf. CoR between 1st and 2nd measurement was respectively 0.61 vs. 0.94 D for Ks, and 0.25 vs. 0.94 D for Kf. CoR of Km and Ks-Kf obtained with the two instruments were similar. In post-LASIK corneas, the rotating Scheimpflug camera provided more reliable measurements of all parameters than Placido disk-based topography. CoR between examiners were respectively 0.21 vs. 0.85 D for Ks, 0.14 vs. 0.78 D for Kf, 0.15 vs. 0.80 D for Km, and 0.17 vs. 0.34 D for Ks-Kf. CoR between 1st and 2nd measurement was 0.15 vs. 0.77 D for Ks, 0.16 vs. 0.80 D for Kf, 0.18 vs. 0.77 D for Km, and 0.19 vs. 0.30 D for Ks-Kf.

Conclusions:

In keratoconic and post-LASIK corneas, the rotating Scheimpflug camera and Placido disk-based topography both provide reliable measurements of anterior corneal curvature. However, measurements obtained using the rotating Scheimpflug camera are slightly more reproducible and repeatable. FINANCIAL INTEREST: NONE

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