Comparison of corneal thickness measurements using ultrasound pachymetry, noncontact tonopachy, Pentacam HR, and Fourier-domain OCT

We retrospectively compared the central corneal thickness (CCT) obtained by ultrasound pachymetry (USP; SP-3000, Tomey Corp., Nagoya, Japan), non-contact tonopachy (TP) (NT-530P, Nidek Co., Ltd., Gamagori, Japan), Pentacam HR (OCULUS Inc., Wetzlar, Germany), and RTVue optical coherence tomography (OCT) (Optovue Inc., Fremont, CA, USA) in 78 eyes of 78 healthy subjects with myopia. Agreement between the measurement methods was evaluated using 95% confidence intervals for the limits of agreement (LoA). The mean CCT values were 546.9 ± 34.7, 548.1 ± 33.5, 559.2 ± 34.0, and 547.2 ± 34.8 μm for USP, non-contact TP, Pentacam, and RTVue, respectively. The thickest and the thinnest mean CCT values corresponded to those obtained by Pentacam HR and USP, respectively. Plots of the differences against the means showed the best agreement between USP and RTVue (LoA, 10.14–10.70 μm), while the largest discrepancy was observed between RTVue and Pentacam systems (LoA, −25.47–1.44 μm). Our data showed that CCT measurements using these 4 instruments were well correlated. However, the results from Pentacam differed significantly from those of the other instruments.