Comparison of Fourier-Domain and Time-Domain Optical Coherence Tomography in the Measurement of Thinnest Corneal Thickness in Keratoconus

Objective. to compare fourier-domain optical coherence tomography (fd-oct) and time-domain oct (td-oct) in the determination of thinnest corneal thickness (tct). methods. this study included 55 keratoconus patients and 50 healthy volunteers. the rtvue-oct (fd-oct) and visante-oct (td-oct) were used for the measurement of the tct. three consecutive scans were performed. the comparison and agreement between the two modalities were analyzed by paired t-test,the pearson correlation,intraclass correlation coefficient (icc),and bland-altman plots. intraobserver repeatability was analyzed by the intraobserver within-subject standard deviation (s (w)),coefficient of variation (cv (w)),and icc. results. the tct value of normal corneas was higher by rtvue-oct (530.4 ± 19.7 μm) than visante-oct (521.5 ± 18.3 μm) (p < 0.001). for keratoconus eyes,the tct was 425.0 ± 58.2 μm and 424.4 ± 55.7 μm (difference being 0.6 ± 10.2 μm,p = 0.604). strong correlation (r = 0.938∼0.985) (icc = 0.915-0.984) was observed between the two octs,and each oct exhibited excellent repeatability in determining the tct in all subjects (icc = 0.984-0.994). conclusions. the values of tct obtained from rtvue-oct and visante-oct were highly correlated; however,the two values were different. both oct instruments exhibited good intraobserver reliability. the existence of systematic differences suggested that the two instruments cannot be used interchangeably. © 2015 chunxiao wang et al.