Repeatability of aberrometric measurements in normal and keratoconus eyes using a new Scheimpflug-Placido topographer.

PURPOSE

To evaluate the repeatability of the anterior and posterior corneal wavefront aberrations using the Sirius Scheimpflug-Placido topographer in normal eyes and keratoconus eyes.

SETTING

Bozok University Faculty of Medicine, Yozgat, Turkey.

DESIGN

Evaluation of diagnostic test.

METHODS

In eyes of healthy subjects and eyes of keratoconus patients, 3 repeated measurements were obtained using the Scheimpflug-Placido topographer. Repeatability of the corneal aberrometric data using a 7th-order Zernike expansion (6.0 mm pupil) and central corneal power (3.0 mm zone) in the anterior and posterior corneal surfaces were analyzed. The within-subject standard deviation (Sw) and the intraclass correlation coefficient (ICC) were calculated.

RESULTS

For all modal pairs, the Sw was 0.08 μm or less for anterior and posterior corneal aberrations in both groups. The ICC of the anterior corneal surface ranged from 0.607 (pentafoil) to 0.988 (primary coma) in keratoconus eyes (n = 41) and from 0.568 (quadrifoil) to 0.856 (primary coma) in normal eyes (n = 30). The ICCs for posterior corneal surface aberrometry were 0.656 to 0.873 and 0.592 to 0.824, respectively. For anterior and posterior corneal curvatures, the Sw was 0.12 or lower and the ICC values were more than 0.93 in all cases except the posterior corneal surface reading at the 3.0 mm corneal area in keratoconus eyes (ICC 0.875).

CONCLUSIONS

The intraexaminer repeatability of most anterior corneal aberrations with the Scheimpflug-Placido system was moderate to high in normal eyes and keratoconus eyes. The system showed moderate repeatability for the posterior corneal surface.

FINANCIAL DISCLOSURE

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