16 Reliability and efficiency of corneal thickness measurements using sterile donor tomography in the eye bank

To evaluate the reliability and efficiency of sterile corneal thickness measurements of donor corneas stored in a plastic culture flask filled with organ culture medium I (MI) or II (MII) based on tomographic data using two different software: the built-in software of the anterior segment OCT (AS-OCT) and a MATLAB self-programmed software.

Twenty-five (25) donor corneas (50%) stored in MI and 25 (50%) in MII were imaged 5 times consecutively using an AS-OCT. The central corneal thickness (CCT) was measured both with the manual measurement tool of the AS-OCT (=CCTm) and with a MATLAB self-programmed software allowing (semi-)automated analysis (=CCTa). We analyzed the reliability of CCTm and CCTa using Cronbach´s alpha (α) and Wilcoxon signed-rank test.

Concerning CCTm, 68 measurements (54.4%) in MI and 46 (36.8%) in MII presented distortions in the imaged 3D-volumes and were discarded. Concerning CCTa, 5 (4%) in MI and 1 (0.8%) in MII were not analyzable. The mean (± SD) CCTm was 1129 ± 6.8 in MI and 820 ± 5.1 µm in MII. The mean CCTa was 1149 ± 2.7 and 811 ± 2.4 µm, respectively. Both methods showed a high reliability with a Cronbach´s α for CCTm of 1.0 (MI/MII) and for CCTa of 0.99 (MI) and 1.0 (MII). Nevertheless, the mean SD of the 5 measurements was significantly higher for CCTm compared to CCTa in MI (p = 0.03), but not in MII (p = 0.92).

Sterile donor tomography proves to be highly reliable for assessment of CCT with both methods. However, due to frequent distortions regarding the manual method, the (semi-)automated method seems to be more efficient and should be preferred.