Comparison of central corneal thickness with ultrasound pachymetry, noncontact specular microscopy and spectral domain optical coherence tomography

Background: To determine the agreement of central corneal thickness (CCT) measurements taken with ultrasonic pachymetry (USP), spectral domain optical coherence tomography (SD-OCT) and noncontact specular microscopy (NSM). Methods: A prospective, observational, cross-sectional study was performed in the outpatient ophthalmology clinic. CCT was measured in a total of 147 eyes of 147 consecutive healthy patients with USP, NSM, and SD-OCT. Same examiner performed all examinations. Bland-Altman plots were used to evaluate the agreement between instruments. Results: The average CCT values obtained by USP, NSM, and SD-OCT were 555 +/- 37 mu m, 554 +/- 34 mu m, and 546 +/- 34 mu m, respectively. There was a strong correlation between instruments: USP with SD-OCT (r = 0.937, p <0.01), USP with NSM (r = 0.943, p <0.01) SD-OCT with NSM (r = 0.975, p <0.01) for CCT. The mean differences (lower/upper limit of agreement) for CCT measurements were -10 +/- 12.9 pm (15.28/-35.28) between SD-OCT and USP-8.1 +/- 7.7 pm (7/-23.2) between SD-OCT and NSM, and 1.8 +/- 12.3 pm (25.9/-22.3) between USP and NSM. Conclusions: USP and NSM were found to have comparable CCT measurements and these two methods can be used correspondingly. However, CCT measurements by SD-OCT were lower when compared to other methods.