Imaging Assessment of Peripapillary Vessel Diameters in Postmortem Eyes

Purpose Proof of concept of ex vivo retinal vessel diameter measurements in human postmortem eyes. Methods En face near-infrared (IR) images and optical coherence tomography (OCT) of the optic nerve head (ONH) were captured ex vivo with a Heidelberg Engineering Spectralis (Spectralis, version 7.0.4, Image Capture Module, version 1.2.4, Heidelberg Heidelberg, Germany) device, using a custom-made eye chamber holding and positioning the eyes during the image process. Thirty-two formaldehyde-fixated eyes of 16 patients were imaged. In the IR images, two independent graders measured retinal vessel diameters at the intersection of a drawn circle centered on the ONH with diameters of 2.0 mm and 3.4 mm, respectively. The anatomically corresponding measurements between both graders were statistically analyzed using a Wilcoxon signed-rank test. Results A total of 246 matched measurements of both graders were analyzed across all 32 imaged eyes. Statistically significant differences between the graders were found for arterioles at 2 mm from the ONH. The other measurements did not show statistically significant intergrader differences. The mean values for arteriole diameters were 72.2 mu m at 2.0 mm and 61.5 mu m at 3.4 mm for grader 1, and 66.4 mu m at 2.0 mm and 63.2 mu m at 3.4 mm for grader 2. The mean diameter for venules were 75.5 mu m at 2.0 mm and 79.3 mu m at 3.4 mm for grader 1, and 67.4 mu m at 2 mm and 79.1 mu m at 3.4 mm for grader 2. Conclusion To the best of our knowledge, this is the first study to present IR image-based retinal vessel diameters in ex vivo postmortem eyes. Retinal IR/OCT imaging is possible, and measurements are reproducible in formaldehyde-fixated human eyes. Fixation artefacts result in lower image quality, and this can impose challenges in correctly detecting, classifying, and measuring retinal vessels.