Comparison of the corneal thickness as measured by Visante® anterior segment OCT versus ultrasound technique

Background: Pachymetry is important in relation to the intraocular pressure (IOP) and can either be contact measured or non-contact measured. Depending on the corneal thickness it is possible to get false IOP measurements up to +/-5 mmHg. Thus, it is necessary to know the exact corneal thickness. A new non-contact technique for measuring the corneal thickness is available with the Visante (R) anterior segment optical coherence tomography (OCT, Zeiss). Methods: Ultrasound as well as the OCT technique is based on beam reflection at optical interfaces. Ultrasound waves or, respectively, coherent light beams (electromagnetic waves) are used for the imaging. Twenty-six patients were examined using the OCT and ultrasound with special emphasis on the corneal thickness and the results compared. Results: The use of OCT to measure the corneal thickness is a safe method. Both techniques give comparable pachymetry results, whereas the OCT technique shows a tendency for lower values. Statistically significant differences could not be shown. Conclusion: OCT is a new, non-contact technique for measuring the corneal thickness. Furthermore, this is a method that does not interact with other measurements like keratometry or corneal topography.