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

Abstract

To evaluate the reliability and efficiency of sterile pachymetric measurements of donor corneas based on tomographic data using two different methods: a “manual” and a “(semi-)automated” method. Twenty-five (25) donor corneas (50%) stored in MI and 25 (50%) in MII were imaged 5 times consecutively using an anterior segment OCT (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 is more efficient and should be preferred.

In situ donor keratometry in deceased patients as a novel screening technique for eye banking

“…Independent of its clinical relevance, in situ keratometry seems to represent a highly repeatable measurement method with regard to the calculated Cronbach's alpha [24]. Sterile donor tomography has also been proven to be highly reliable for the assessment of the corneal thickness with both a manual and the (routinely used) semiautomated method [25]. The repeatabilty of the curvature measurement with sterile donor tomography is currently being investigated in our eye bank.…”

Culturing Limbal Epithelial Cells of Long-term Stored Corneal Donors (Organ Culture) In Vitro – A Stepwise Linear Regression Algorithm

“…Thereafter, as a second step, before corneal transplantation and before initiation of the LEC cultures, corneoscleral buttons were stored up to 4 days in medium II (with the same ingredients as medium I but with the addition of dextran T500 6%). With dextran T500 6%, the osmolarity of the organ culture medium changed from 307 to 353 mOsmol/kg, turning the medium to a hyperosmotic solution that allows deswelling of the donor corneal tissue 35 , 36 , 37 , 38 , 39 . Along our results, the number of culture medium changes during organ culture should be as low as possible for a successful in vitro limbal stem cell culture.…”

Review for special issue: Corneal lamellar surgery: Present outcomes and future perspectives

“…A more recent concept, known as “sterile donor tomography,” sterilely measures the organ-cultured cornea stored in a cell culture flask using the swept-source anterior segment-optical coherence tomography (AS-OCT) [ Figure 7 ]. [ 43 44 ] A raster scan is generated from the back surface of the donor cornea, creating a 3D volume dataset with a depth resolution of 5.621 μm/voxel in aqueous medium and a lateral resolution of 6 μm/voxel. [ 45 ] Thereafter, the measured raw data are loaded into MATLAB (MathWorks Inc., Natick, Massachusetts, USA) and pretreated to remove artifacts induced by the culture flask wall and the tissue holder, extract background noise, adjust the contrast size, minimize the brightness of the central reflection, and identify the edge of the front and back surfaces of the donor cornea.…”