Authors: Etienne Vachon-Joannette, Patricia Ann Laughrea, Marie Eve Légaré, Patrick Carrier, Jeanne d'Arc Uwamaliya, Mathieu Thériault, Stéphanie Proulx
Author Disclosure Block: E. Vachon-Joannette: None. P. Laughrea: Membership on advisory boards or speakers’ bureaus; Sanofi-Genzyme. Membership on advisory boards or speakers’ bureaus; Description of relationship(s); Speaker. M. Légaré: None. P. Carrier: None. J. Uwamaliya: None. M. Thériault: None. S. Proulx: None.

Abstract Body:

Purpose: The evaluation of corneal tissue quality before transplantation is assessed, in part, using endothelial cell density (ECD) obtained at the specular microscope. The central corneal endothelium is analyzed (a fraction of the endothelial population) and ECD is extrapolated. Ambiguity in this count is related to the indistinct cell margins, making the count somewhat imprecise. Our study aims to compare the different parameters provided by endothelial specular microscopy with those provided by alizarin red staining to determine if there is a significant difference between these two methods.
Study Design: Prospective observational study.
Methods: A sample of 78 corneas ineligible for transplantation was analyzed using both specular microscopy and alizarin red staining. Four central endothelial areas were analyzed for each method and merged in a respective average. Endothelial cell density, coefficient of variation and the % of hexagonal cells were analyzed using the KSS-EB10 software for each of the methods studied. Different variables (age, gender, laterality, time interval between death and analysis) were reviewed in order to make a descriptive analysis. After ensuring that the data followed a normal distribution, the count values were compared with each other using a paired Student t test. A regression model based on generalized estimating equations was used to study the impact of each variable on the associated count. Finally, the use of a positive control helped validate the reliability of the measures made in specular microscopy and conventional microscopy.
Results: A statistically significant lower density of 155 cells / mm (p <0.0001) was obtained for alizarin red measurements compared to those obtained using specular microscopy. Staining with alizarin red also demonstrated a higher coefficient of variation (+0.85, p = 0.0227) whereas the specular microscopy demonstrated a higher rate of hexagonality (+1.13%, p = 0.0400). ECD was correlated with age, but no significant correlation was found according to donor gender, laterality or the time interval between the death and the analysis.
Conclusions: This study demonstrates a statistical and clinical relevant difference between the specular microscope and alizarin red staining. Thus, according to the respective criteria of eye banks, endothelial count of eligible corneas for transplant might be overestimated, compromising graft survival in corneas with borderline ECDs.