When astronauts return to the Earth after a long duration space missions they suffer from several physical issues.Over the last decade,  scientists and flight surgeons at NASA have noticed a pattern of vision impairments among Astronauts on long-duration space missions.

According to recent studies, this problem occurs because of the drastic volume changes in clear fluid which are found around the spinal cord and brain. This syndrome is called Visual Impairment Intracranial Pressure (VIIP), reports say that among two thirds of space explorers experience this medical condition after landing back to Earth from a long-term space journey.

 A human body evolved to stay fit for Earth's gravity (9.81m/s^2) but during the space mission, it becomes Zero. On Earth, Cerebrospinal Fluid (CSF) of a human body can accommodate sudden changes of pressure, such as changing postures like rising up from sleeping or sitting position. But in outer space where there is no gravity that pulls the body to ground, the body system becomes confused by the lack of posture-related pressure changes.

A research team from University of Miami Miller School of Medicine found that microgravity triggers the Cerebrospinal Fluid (CSF) towards the brain and causes Astronauts' eyeballs to flatten, which leads to Myopia or nearsightedness. Building up of CSF also causes Optic nerves to sticks out. The optic nerve carries visual information from retina to brain ,which is also not good. Optical nerve failure can cause permanent eye damages.

"People initially did not know what to make of it, and by 2010 there was growing concern as it became apparent that some of the astronauts had severe structural changes that were not fully reversible upon return to Earth," said by the lead author of this study Dr.Noam Alperin.

Pointing at those issues Scientists are now focused in finding better ways to prevent this from happening again. Researchers are assuming that generating Artificial Gravity during the mission will become the primary solution but it still needs further research. The truth is, it's a problem with no clear solution till now. In the meantime, space will continue to be a discouragingly inhospitable place for humans.