Comparison of central corneal thickness using optical low-coherence reflectometry and spectral-domain optical coherence tomography

PURPOSE: To assess intraobserver and interobserver reliability of central corneal thickness (CCT) measurements using optical low-coherence reflectometry (OLCR) technology and its agreement with spectral-domain optical coherence tomography (SD-OCT). SETTING: Rio Hortega University Hospital, Valladolid, Spain. DESIGN: Evaluation of diagnostic technology. METHODS: To analyze OLCR intraobserver repeatability, 1 examiner obtained 4 successive measurements. To study interobserver reproducibility, a different examiner obtained another CCT measurement. To determine agreement with SD-OCT, the first examiner also obtained CCTs. Intraobserver and interobserver within-subject standard deviation (S-w), coefficient of variation (CVw), and limits of agreement (LoA) were obtained for OLCR reliability analysis; for study agreement, data were analyzed using the paired-sample t test and the LoA were calculated. RESULTS: For OLCR intraobserver repeatability, the S, and precision (1.96 x S-w) were 2.33 and 4.56 mu m, respectively. The intraobserver CVw was 0.42%. For interobserver reproducibility, the S and precision were 11.59 and 22.71 mu m, respectively; the CVw was 2.10%. The mean difference between observers was -1.35 mu m (95% confidence interval [CI], -3.97 to 1.26). The width of the LoA was 45.27 mu m. The mean CCT difference between OLCR and SD-OCT was 5.68 +/- 11.46 mu m (95% CI, 8.29-3.08 mu m; P=.0001), and the width of the LoA was 44.93 mu m. CONCLUSIONS: Optical low-coherence reflectometry technology provided reliable intraobserver and interobserver CCT measurements. Although OLCR underestimated the pachymetry by less than 6 pin compared with SD-OCT, its interchangeability fell within the range of interobserver reproducibility. Both noncontact pachymetry measurements seem to be clinically useful and may be used interchangeably with minimum calibration adjustment.