Late increase in corneal thickness after DMEK: A localized phenomenon?

Abstract

Purpose : In a previous study, we observed a statistically significant increase in central corneal thickness (CCT) between one and two years as well as between two and three years after Descemet membrane endothelial keratoplasty (DMEK). Since corneal endothelial cell density (ECD) remained stable during this period, the reason for this finding was unclear. Therefore, the aim of this study was to investigate whether corneal thickness increases only in the center or throughout the entire cornea.

Methods : We performed a retrospective single-center study including 46 eyes of 39 patients who underwent DMEK surgery. ECD was assessed using specular microscopy (SeaEagle, HAI Laboratories, Lexington, MA, USA) and CCT as well as corneal thickness on a 4 mm- and 8 mm-diameter ring around the corneal apex were analyzed by Scheimpflug imaging (Pentacam, Oculus, Wetzlar, Germany). In total, corneal thickness was measured at 33 spots. These were used to calculate mean corneal thickness (MCT₃₃) and the coefficient of variation (CV₃₃) of corneal thickness. Data were collected for the 1^st, 2^nd, 3^rd and 4^th year after DMEK. Wilcoxon rank sum test was used to compare different periods.

Results : ECD was stable throughout all periods analyzed in this study. Between year one and year two, CCT (p=0.004) as well as MCT₃₃ (p=0.011) increased significantly while CV₃₃ decreased significantly (p=0.016). During the following year there was a further significant increase of both CCT (p=0.002) and MCT₃₃ (p=0.012) while CV₃₃ remained stable. Between years three and four no significant changes of CCT, MCT₃₃ and the CV₃₃ of corneal thickness were observed.

Conclusions : Increase in corneal thickness after DMEK is not confined to the center but rather affects the entire cornea as increase in CCT is associated with an increase in MCT₃₃. Furthermore, CV₃₃ decreases between year one and year two showing that the distribution of corneal thickness becomes more homogenous. Accordingly, it appears unlikely that a localized dysfunction of the corneal endothelium would account for the increased thickness observed.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.