Figure 1.

Experimental Setup and image. (A) The experimental setup. The EpiCam M is a hand-held digital retinal fundus camera, which is aimed directly at the pupil, from where the vessels can be visualized. This figure shows a schematic setup of the experimental setup. The video capturing occurs during infusion test through a needle in the lumbar region. (B) The optic disc and vessels. To distinguish arterioles and venules it is important to know two things: 1. Arterioles never cross arterioles and venules never cross venules and 2. Venules are generally larger and darker than arterioles. If the images are of high enough quality one can observe pulsation through the arteriole and thereby making proper vessel identification easy.