Central corneal thickness measurement with the Pentacam Scheimpflug system, optical low-coherence reflectometry pachymeter, and ultrasound pachymetry

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Abstract
To assess the intraoperator repeatability and interoperator reproducibility of central corneal thickness measurements by the Pentacam Scheimpflug imaging system (Oculus) and the optical low-coherence reflectometer (OLCR) pachymeter (Haag-Streit) and to compare them with those of ultrasound (US) pachymetry. Assaf Harofe Medical Center Ophthalmology Outpatient Clinic, Zerifin, Israel. Repeatability was determined from 10 successive measurements in each of 4 healthy patients. Reproducibility for the Pentacam Scheimpflug system was determined from measurements by 2 operators in each of 24 patients; in these 24 patients, central corneal thickness measurements were compared between the Pentacam and US pachymetry. For the OLCR pachymeter, reproducibility was determined from measurements by 2 operators in each of 16 patients, in whom central corneal thickness was also measured with the Pentacam. Mean coefficient of repeatability was 0.84% for the Pentacam Scheimpflug system and 0.33% for the OLCR pachymeter. For the Pentacam, the coefficient of interoperator reproducibility was 1.10% and the 95% limits of agreement were -10.2 microm to +11.9 microm. Mean difference between Pentacam and US was 6.09 microm. For the OLCR pachymeter, the coefficient of interoperator reproducibility was 0.59% and the 95% limits of agreement were -5.4 microm to +7.0 microm. Mean difference between central corneal thickness values obtained with the OLCR pachymeter and Pentacam Scheimpflug system was 1.7 microm. Objective, noncontact measurement of central corneal thickness with the Pentacam Scheimpflug system and OLCR pachymeter was convenient and yielded excellent intraoperator repeatability and interoperator reproducibility. Central corneal thickness values obtained with the Pentacam were similar to those obtained with both the OLCR pachymeter and an US pachymeter. Further research is needed to corroborate whether central corneal thickness measurements by the Pentacam and OLCR devices can be used interchangeably and are more clinically useful than US pachymetry.