Central corneal thickness measurement with online optical coherence pachymetry and ultrasound pachymetry in 513 consecutive eyes

BACKGROUND: The aim of this study was to assess the reliability of online optical coherence pachymetry (OCP) integrated into the Technolas excimer platform by comparing the intraoperative OCP corneal thickness measurement with the preoperative standard ultrasound pachymetry (USP). PATIENTS/MATERIALS AND METHODS: The mean central corneal thickness of 513 consecutive eyes was measured using OCP and USP. Immediately before starting the LASIK procedure, three OCP measurements of the central cornea (OCPonline, Heidelberg Engineering GmbH, Germany) were done under the microscope of the Excimer laser (Technolas, Bausch and Lomb, Rochester, NY). The mean value of 10 central USP measurements (Sp-3000, Tomey, Japan) was obtained during the preoperative assessment of the patients. The comparison of the two methods was done using Pearson regression analysis and the Bland- Altman method. RESULTS: Mean central corneal thickness of the OCP and the USP were 523.1 ± 30.5 μm and 561.2 ± 32.7 μm, respectively. The correlation coefficient was r = 0.891 for the two methods. The mean difference between USP and OCP was 37.9 ± 14.8 μm. CONCLUSIONS: The intraoperative OCP gives 7 % smaller measurements compared with the preoperative USP.