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

الملخص EN

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.