Repeatability and reproducibility of a new method for centration analysis via optical zone tangent points after corneal refractive surgery

To investigate the repeatability and reproducibility of a new method for centration analysis after small incision lenticule extraction (SMILE) and femtosecond laser-assisted LASIK (FS-LASIK).

This study comprised 29 eyes treated with SMILE and 24 with FS-LASIK. Decentrations were analyzed using tangential and pachymetry difference maps respectively. Both difference maps were generated with a Scheimpflug tomographer (Pentacam) for each eye, using preoperative and 3-month postoperative scans. Repeatability and reproducibility were evaluated by calculating the intraclass correlation coefficient (ICC), within-subject standard deviation (Sw), and coefficient of repeatability (CR).

ICC, Sw, and CR showed good to excellent repeatability in locating the coordinates of the optical zone (OZ) center on both maps, with values ranging from 0.84 to 0.96, 0.03 to 0.13, and 0.08 to 0.36 respectively. The repeatability of the total decentration from the preoperative corneal vertex on the tangential curvature difference maps( \(d_{TC}\) $d_{\mathit{TC}}$ ) and the pachymetry difference maps( \(d_{PC}\) $d_{\mathit{PC}}$ ) were moderate and good, respectively. The ICC, Sw, and CR of \(d_{TC}\) $d_{\mathit{TC}}$ were 0.63, 0.09, and 0.25, respectively. The ICC, Sw, and CR of \(d_{PC}\) $d_{\mathit{PC}}$ were 0.77, 0.10, and 0.28, respectively. The reproducibility of the OZ center measurements was excellent for the tangential difference maps (ICC \(\ge 0.97\) $\ge 0.97$ ) and good for the pachymetry difference maps (ICC \(\ge\) $\ge$ 0.86). ICC, Sw, and CR showed excellent reproducibility of \(d_{TC}\) $d_{\mathit{TC}}$ , with values of 0.95, 0.03, and 0.08, respectively. ICC, Sw, and CR showed good reproducibility of \(d_{PC}\) $d_{\mathit{PC}}$ , with values of 0.89, 0.06, and 0.17, respectively.

The centration analysis method used in this study showed good to excellent repeatability and reproducibility in locating the coordinates of the center of the OZ on the tangential and pachymetry difference maps.