Intrasubject repeatability in keratoconus-eye measurements obtained with a new Scheimpflug photography-based system.

PURPOSE

To evaluate in keratoconus eyes the intrasubject repeatability of anterior and posterior corneal curvature and of other anterior segment anatomic measurements obtained with a new topography system combining Scheimpflug-photography and Placido-disk technology.

SETTING

Vissum Corporation, Alicante, Spain.

DESIGN

Evaluation of technology.

METHODS

All keratoconus eyes had a comprehensive ophthalmologic examination including analysis with the Sirius system. Three consecutive measurements were obtained to assess the intrasubject repeatability of the following parameters: anterior and posterior corneal curvature and shape factor, white-to-white (WTW) corneal diameter, central and minimum corneal thickness, and anterior chamber depth (ACD). The within-subject standard deviation (S(w)) and intraclass correlation coefficient (ICC) were calculated.

RESULTS

This study comprised 61 eyes of 61 patients ranging in age from 14 to 64 years. For anterior and posterior corneal curvatures and power vector components, the S(w) was 0.29 mm or less in all cases. The ICC was above 0.990 in all cases except the flattest curvature of the posterior corneal surface at 3.0 mm, which was 0.840 (moderate agreement), and the posterior power vector J0, which was 0.665 (poor agreement), 0.752, and 0.758 (moderate agreement) for 3.0 mm, 5.0 mm, and 7.0 mm, respectively. In shape factor measurements, the S(w) was 0.12 or less in all cases and the ICC ranged between 0.989 and 0.999. Pachymetry, ACD, and WTW had ICC values very close to 1.

CONCLUSION

The new topography system provided repeatable measurements of corneal shape and other anatomic parameters in eyes with keratoconus.

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned.