Effect of gravity and microgravity on intracranial pressure

Astronauts have recently been discovered to have impaired vision, with a presentation that resembles syndromes of elevated intracranial pressure on Earth. Gravity has a profound effect on fluid distribution and pressure within the human circulation. In contrast to prevailing theory, we observed that microgravity reduces central venous and intracranial pressure. This being said, intracranial pressure is not reduced to the levels observed in the 90 deg seated upright posture on Earth. Thus, over 24 h in zero gravity, pressure in the brain is slightly above that observed on Earth, which may explain remodelling of the eye in astronauts.