Endothelial cells analysis with the TOPCON specular microscope SP-2000P and IMAGEnet system

Purpose. Corneal endothelium plays an important role in the maintenance of corneal transparency and stability. The purpose of this study was to evalua te the performance of the TOPCON SP-2000P and IMAGEnet system in terms of ( a) the difference in results between automated endothelial cell analysis an d retraced cell analysis, (b) the differences in the endothelial cell analy sis when using the first image and the clearest of three images taken with the SP-2000P, (c) the repeatability and reproducibility of the IMAGEnet sys tem in the determination of corneal endothelial cell variables, and (d) the repeatability and reproducibility of the SP-2000P in capturing endothelial cell images for endothelial cell analysis. Methods. Two experiments were performed. Twenty male subjects participated in the first experiment in which endothelial images were captured by examin er SWC and endothelial cell analysis was performed by two examiners, SWC (t wice on two different days) and PC (once only). Nineteen male subjects part icipated in the second experiment in which endothelial cell images were cap tured by examiners SWC and PC on Visit 1 and by examiner SWC on Visit 2. En dothelial cell analysis was performed by examiner SWC only. The 95% limits of agreements (95% LA) and the intraclass correlation coefficient (ICC) bet ween tested parameters were determined. Results. Automated cell analysis significantly underestimated average cell size (ACS) and hexagonality, and overestimated endothelial cell density (EC D) and coefficient of variance of cell size (CV) (p < 0.05). No statistical ly significant differences were found in the endothelial cell variables bet ween the first and the clearest images (p > 0.05). There were no statistica lly significant intra- or inter-examiner differences in any of the endothel ial variables determined (p > 0.05). For a set of endothelial cell images, the reproducibility and repeatability of the endothelial cell variables det ermined with the IMAGEnet system were good, with ICC > 0.9. No significant inter-visit or inter-examiner differences were found (p > 0.05). Reliabilit y was good for the determination of ECD and ACS (ICC > 0.9) but poor or ave rage for the determination of CV and hexagonality (ICC: 0.4-0.8). Conclusions. We suggest the use of the clearest image with the retraced met hod for endothelial cell analysis with the IMAGEnet system, as the variabil ity in hexagonality results between the first and the clearest images can b e clinically significant. For the same set of images captured by one examin er, the TOPCON IMAGEnet system was reliable in determining ECD and ACS, and was fairly reliable in determining hexagonality and CV. When images were c aptured on different days or by different examiners, the TOPCON SP-2000P wi th the IMAGEnet system gives repeatable and reproducible values for ECD and ACS only. Caution should therefore be exercised when using CV and hexagona lity to monitor endothelial changes in comparative studies.