Precision of Corneal Aberrometric Measurements With a New Hybrid Device and Comparison With a Scheimpflug/Placido Topography in Different Grades of Keratoconus.

Abstract

Purpose: To assess the precision of corneal higher order aberration (HOA) measurements obtained by an anterior segment optical coherence tomographer combined with Placido-disk topography (MS-39) in different grades of keratoconus and compare them with a Scheimpflug/Placido topographer (Sirius).

Methods: Anterior, posterior, and total corneal aberrations were analyzed. Within-subject standard deviation (S_w), test-retest repeatability (TRT), and intraclass correlation coefficient (ICC) were used to assess the intraobserver repeatability and interobserver reproducibility. The differences between the two devices were evaluated using the paired t-test. Bland-Altman plots and 95% limits of agreement (95% LoA) were applied for agreement analysis.

Results: This prospective study included 99 eyes of 99 patients with keratoconus. Regarding intraobserver repeatability, all S_w values were 0.16 µm or less, TRT 0.44 µm or less, and ICCs 0.874 or greater for anterior and total corneal parameters. For posterior corneal aberrations, all S_w values for high-order Zernike terms were 0.04 µm or less and ICCs varied from 0.739 to 0.991. Regarding interobserver reproducibility, all S_w values were 0.17 µm or less and TRT 0.29 µm or less. ICCs ranged from 0.956 to 0.998, from 0.84 to 0.997, and from 0.923 to 0.997 for anterior, posterior, and total corneal aberrations, respectively. The TRT of the Zernike coefficients tended to improve with increasing keratoconus stage. All parameters showed a narrow 95% LoA and varied according to the keratoconus stages.

Conclusions: The new hybrid MS-39 device provides precise measurements for almost all corneal aberrations in different grades of keratoconus. The MS-39 and Sirius can be used interchangeably for measuring corneal aberrations. [J Refract Surg. 2025;41(5):e460-e471.].