According to a recently published study, the main cause of astronauts' vision impairment is the negative effect of microgravity (weightlessness) on intracranial pressure. Addressing this problem is critical in view of the start of preparations for a manned mission to Mars by 2030.
In particular, the researchers argue that the deterioration of astronauts' vision is facilitated by the constant intracranial pressure accompanying the state of weightlessness. This was established by the results of a study of eight volunteers who underwent specific treatment for brain cancer using the so-called Ommaya reservoir, which is a thin silicone catheter with a special port.
To simulate microgravity, several parabolic flights were carried out, during which the participants in the experiment received their "portion" of weightlessness for 20 seconds.
The scientists compared the readings of intracranial pressure at the moment of weightlessness with the readings when the subjects were lying face up or down in a laboratory. It was found that in zero gravity the readings were slightly lower than "earthly" ones.
It is known that the pressure in the back of the eye changes at different times of the day. When a person is standing, the pressure inside the skull is minimal, but it increases in the supine position.
Parabolic flights have shown that pressure cycles remain unchanged under zero gravity. Prolonged stay in this state, in particular on the ISS, is fraught with negative consequences for vision.
To recreate the "earth" cycles on board the spacecraft, the researchers suggested using a special negative pressure chamber that would be worn on the lower body. With its help, the outflow of blood from the head and below the heart will be ensured, just as it happens under normal gravity.