97th DOG Annual Meeting 1999



C. Wirbelauer, H. Hoerauf, C. Scholz*, G. O. Bastian, R. Birngruber*, H. Laqua

Introduction: The representation of the cornea is an important part of the ophthalmologic examination and particularly in refractive surgery. The purpose of this study was to investigate the accuracy of two-dimensional corneal thickness representation using optical coherence tomography (OCT).

Patients and Methods: In a controlled clinical study 39 patients without corneal pathologies were consecutively studied. Non-contact pachymetry of the central cornea was performed with a slitlamp-adapted OCT system (Schwind, Kleinostheim). Controls were determined at 1640 m/s with two different ultrasound pachymetric systems (US). Since our reference methods have no absolute precision structural regressions, equivalence tests, and the Bland-Altmann method were used for statistical analysis.

Results: The mean corneal thickness values were 546±41 µm (US) and 539±37 µm (OCT) with a mean coefficient of variation of 0.8% (US) and 1.2% (OCT). The method comparison revealed equivalence (±2SD) in the 5% range for the bivariate calibration line (y=0.6+0.99x) of the structural regression. The mean bias indicated a slight underestimation with OCT pachymetry of 6.6 µm (1.2%). The precision (±SD) was 11 µm, which corresponded to an error (±2SD) of 4.1%.

Conclusions: The representation of the corneal thickness with OCT revealed a good agreement with ultrasound pachymetry. Thus, two-dimensional corneal OCT is a useful additional parameter, which can be rapidly measured in a convenient non-contact mode using the slitlamp.

Augenklinik der Medizinischen Universität zu Lübeck
*Medizinisches Laserzentrum Lübeck GmbH