A bunch of us are working on the fluid shifts experiment to see how our eye and brain-pressure changes in weightlessness. For scientists, the more data the better! We need to be careful about how fluids shift when we return to Earth, as our bodies have been living in weightlessness for six months our heart is not used to pumping blood to the brain against gravity! That is one of the reasons we exercise so much up here. Much progress has been made and generally astronauts who land back on Earth feel fine! https://www.nasa.gov/mission_pages/station/research/experiments/1257.html