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 µm, 554 ± 34 µm, and 546 ± 34 µm, 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 µm (15.28/-35.28) between SD-OCT and USP, -8.1 ± 7.7 µm (7/-23.2) between SD-OCT and NSM, and 1.8 ± 12.3 µm (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.