European Study On Reliability Assessment Of Endothelial Cell Count In Eye Banks: The Eurokeratotest Study

Abstract

Purpose: : In European eye banks, 15 to 20% of corneas are discarded for endothelial cell density (ECD) below 2000 cells/mm². Given the importance of having a precise, robust and reproducible ECD counting method, we organized an international European survey of the quality of ECD determination.

Methods: : The study, named "EuroKeratoTest", reproduced two surveys driven in 2003 and 2008 by our team in the 18 French eye banks (Transplantation2004;78:1299), with substantial improvements. Test slides (Keratotests) were fabricated with technologies employed in micro-optics, from images of real human corneas (Optics Letters2011, in press). They perfectly reproduced the human corneal endothelial mosaic, with chrome deposits on quartz wafers, and could be mass-produced. Twelve different mosaics with ECDs covering the usual range observed in eye banks, were created in a 8x8 mm quartz square. Keratotests were easily observable with transmitted light or specular microscopes. They were sent simultaneously to all volunteer European eye banks (n=100). Each technician of each eye bank had to determine ECD and cell morphometry of the 12 mosaics using the standard counting method he/she employed. Data were collected thanks to a specific website. After data analysis, strategies to improve counting reliability were discussed with eye banks having the highest variability and /or error (systematic under or over estimation). Six month later a second set of keratotests were sent again to verify the stability or the improvement of the ECD counts.

Results: : Using micro-optics methods, we created a specific tool to assess the reliability of endothelial cell count in eye banks. Inter and intra bank variability was easily highlighted. Identification of errors in counting methods or in microscope calibration was possible.

Conclusions: : Participation of the eye banks to this survey that used the new "keratotests technology" improves our knowledge on the reliability of endothelial cell counting methods in European eye banks, and help standardize corneal graft quality assessment. Keratotests also appear as a perfect tool for the initial formation and continuous training of eye banks technicians, as well as for the eye banks certification.

Keywords: cornea: endothelium • cornea: storage • transplantation