Fig. 2.

A practical application of the selfretinal vascular imaging technique in microgravity research. a The same image as in figure 1b was compared with the selffundus photograph obtained during bedrest, after 45 min of supine bedrest with 6° of head-down tilt. Caliber of the superior temporal retinal artery (stra) and superior temporal retinal vein (strv) in the same anatomic location (arrows) was measured with NIH image J 1.39t image analysis software in pixels. The measurement reveals a wall diameter of 25,554 and 29,120 pixels for stra and strv, respectively, in standing position. b Following 45 min of supine bedrest with 6° of head-down tilt (HDT) a reduction of vascular caliber to 24,498 and 27,893 pixels was noted for stra and strv, respectively.