[Concept for 3D measurement of corneal donor tissue using a clinical OCT]

We present a concept for non-contact tomographic measurement and characterization of corneal donor tissue within the cell culture medium. The purpose is to screen corneal tissue for pathologies or alterations after refractive surgery.

Image acquisition is performed with the clinical anterior segment optical coherence tomography (OCT) Casia 2 (Tomey Corp., Nagoya, Japan). An edge detection of the anterior and posterior surfaces of the donor cornea is performed after preprocessing and noise reduction of the data. A sphero-cylindrical surface model is then fitted to the detected surfaces in order to determine the radius of curvature, the surface refractive values, the keratometer readings and central thickness of the cornea. A cornea phantom with defined geometry was used to validate the algorithm and finally 74 donor corneas were measured in the cell culture flask.

The large axial measurement range of the OCT enables measurement of the phantom and tissue samples within the culture flask with a diameter of approximately 7 mm. The developed program reliably removes artifacts caused by the wall of the flask and those originating from the tissue holder and facilitates calculation of the sphero-cylindrical model for the anterior and posterior surfaces. The measurement results for the phantom show minimal deviations from the manufacturer's data. The measured radius of curvature of the corneas was within normal limits.

The anterior OCT Casia 2 enables rapid 3‑dimensional measurement of corneal donor tissue in the culture medium. The measurable range covers approximately 7 mm of the graft diameter, which is mainly limited by the holder used for the donor tissue. Topographical and pachymetric parameters could be derived from the volume data.