Corneal thickness measurements with the Concerto on-board pachymeter

Purpose: To assess the Concerto excimer laser on-board pachymeter (COP) measurements of the central corneal thickness (CCT), central stromal thickness (CST) and flap thickness (FT) in terms of repeatability and agreement with the Pentacam and ultrasound pachymetery. Methods: Patients undergoing photorefractive keratectomy (PRK), PRK with mitomycin-C (MMC), and laser in situ keratomileusis (LASIK) were enrolled in the study. All eyes had CCT measurement with the Pentacam, the COP, and ultrasound, preoperatively. In the LASIK group, the CST was measured intraoperatively with the COP and ultrasound, after removing the flap. Each measurement was done 3 times to study the repeatability, and we calculated the 95% limits of agreement (LoA) for paired readings. Results: The study sample comprised of 82 eyes of 41 patients. All three devices showed excellent repeatability with intraclass correlation coefficients between 0.946 and 0.993. Mean CCT was 546 ± 31 μm with the COP, and 548 ± 32 μm and 548 ± 34 μm with the ultrasound and Pentacam, respectively. COP readings demonstrated high correlations with their paired ultrasound and Pentacam readings. The 95% LoA between COP and ultrasound were −16.6 μm to 12.0 μm for CCT, −25.6 μm to 26.2 μm for CST, and −29.5 to 21.3 μm for FT. The 95% LoA between COP and Pentacam CCT readings were −15.1 μm to 10.1 μm. Conclusions: COP generated repeatable readings that were highly correlated with their pair readings by the Pentacam and ultrasound. Although the agreement between COP and ultrasound was better with CCT measurements, the inter-device agreement for CST readings was not worse than that reported in other comparative studies of pachymeters