PURPOSE: The purpose of this study was to determine the accuracy, the reproducibility, and the limits of agreement of noncontact central corneal thickness measurement with slit lamp-adapted optical coherence tomography (OCT).

DESIGN: Nonrandomized comparative clinical trial.

METHODS: In a prospective comparative observational study, a total of 108 consecutive patients (108 eyes) with normal corneas (92 eyes) and different corneal alterations (16 eyes) participated. Six sequential measurements of the central corneal thickness with slit lamp-adapted OCT and with ultrasound (US) pachymetry at 1640 ms⁻¹ were performed. The main outcome measures were accuracy, reproducibility assessed with precision and coefficient of variation (CV), and limits of agreement of central corneal thickness measurement.

RESULTS: The mean central corneal thickness values were 541 ± 43 μm (OCT) and 549 ± 44 μm (US) with a mean precision of ± 5.8 μm (CV 1.08%) and of ± 4.0 μm (CV 0.73%), respectively. The method comparison revealed equivalence (± 2SD) in the 5% range with a mean difference between both methods of 7.9 μm (1.45%). The relative error was 8.7 μm (1.6%), which corresponded to limits of agreement (± 2SD) ranging from −9.5 μm to 25.3 μm.

CONCLUSIONS: Central corneal pachymetry with slit lamp-adapted OCT revealed, for clinical purposes, an excellent accuracy and reproducibility with a high degree of agreement compared with US pachymetry. Thus, the presented OCT system seems to be a promising diagnostic modality to objectively measure corneal thickness in a convenient noncontact mode.