2.3. Spectral-Domain-Optical Coherence Tomography

We acquired 6 mm-wide SD-OCT scans (Optovue RTVue-100®; Optovue Inc®, Fremont, California, USA) with the long corneal adaptor module (CAM-L) in the center of the cornea. Scans had an axial resolution of 5 μm and a transverse resolution of 15 μm. Corneal adaptor module software automatically processes the OCT scans to provide the epithelial thickness map in the central 6 mm. The proper examination centration was achieved by focusing the OCT scan on the corneal vertex detected by a hyper-reflective wide line perpendicular to the corneal surface.

For both OCT devices, corneal epithelial thickness is measured as the distance between the air-tear and the epithelium-Bowman's layer interfaces perpendicular to the anterior surface at the point of measurement. An epithelial thickness profile is generated from each meridional cross section.