Dependability of Pachymetry Measurements after Myopic Advanced Surface Ablation Using Scanning-Slit Topography and Specular Microscopy
Investigative Ophthalmology and Visual Science
PURPOSE. To assess the repeatability, intersession and interobserver reproducibility, and agreement of central corneal thickness (CCT) measurements obtained by scanning-slit topography (SST) and noncontact specular microscopy (NCSM) after advanced surface ablation (ASA). METHODS. To analyze repeatability, one examiner measured 63 post-myopic ASA eyes five times successively using both techniques randomly. To calculate interobserver reproducibility a second examiner obtained another CCT
... nother CCT measurement in a random fashion. To study intersession reproducibility, the first operator obtained CCT measurements from another 24 eyes during two sessions 1 week apart. RESULTS. With regard to intrasession repeatability, SST and NCSM within-subject standard deviation (S w ) and intraclass correlation coefficient (ICC) were 7.35 and 3.81 lm, and 0.97 and 0.99, respectively. For interobserver reproducibility, SST measurement variability showed correlation with CCT magnitude (r s ¼À0.38; P ¼ 0.002), whereas NCSM did not. NCSM S w and ICC were 3.83 lm and 0.99, respectively. For intersession reproducibility, no difference in CCT measurements was found for any technique; S w and ICC estimates for SST and NCSM were 12.2 and 8.37 lm, and 0.94 and 0.95, respectively. We found a tendency for the difference (mean SST-NCSM ¼ 13.39 lm) to increase in thicker corneas (r s ¼ 0.45, P ¼ 0.001).