Intradevice Repeatability and Interdevice Comparison of Two Specular Microscopy Devices in a Real-Life Setting: Tomey EM-4000 and Nidek CEM-530.

Background and Objectives : The purpose of this study was to compare two commercially available specular microscopes (Tomey EM-4000 and Nidek CEM-530) in a real-life clinical setting in terms of intra- and interdevice variability. The study was conducted on all patients seen in a clinical practice specializing in anterior segment pathologies, regardless of the purpose of their visit. Materials and Methods : In total, 112 eyes of 56 patients (age 23-85 years old) were included in the study. Each eye was measured three times with each device (for a total of six measurements), and results for central corneal thickness (CCT) and corneal endothelial cell density (ECD) were recorded. The results were then evaluated with the D'Agostino-Pearson normality test and compared with a Wilcoxon signed-rank test, t -test, ANOVA or Mann-Whitney test for intra- and interdevice variability. Results : Both specular microscopes produced very reliable reproducible intradevice results: The Tomey EM-4000 measured an ECD of 2390 ± 49.57 cells/mm 2 (mean ± standard error of mean); the range was 799-3010 cells/mm 2 . The determined CCT was 546 ± 5.104 µm (mean ± standard error of mean [SEM]); the range was 425-615 µm. The measurements with the Nidek CEM-530 revealed an ECD of 2417 ± 0.09 cells/mm 2 (mean ± SEM); the range was 505-3461 cells/mm 2 (mean ± SEM). The mean CCT detected was 546.3 ± 4.937 µm (mean ± SEM); the range was 431-621 µm. The interdevice differences were statistically significant for both parameters, ECD ( p = 0.0175) and CCT ( p = 0.0125) ( p < 0.05). Conclusions : The Nidek CEM-530 and the Tomey EM-4000 both produced reliable and reproducible results in terms of ECD and CCT. The absolute measurements were statistically significantly different for CCT and ECD for both devices; the Nidek produces slightly higher values.