Why astronauts vision deteriorates?

Why astronauts vision deteriorates?

Long space flights seem to cause confusion with the astronauts' vision under microgravity conditions. Researchers believe that the cerebrospinal fluid is to blame.

A few months later, during a semiannual flight in space in 2009, Canadian astronaut Bob Sersk ran into trouble reading the loading lists on the International Space Station, which are printed in the 8th point of the font. Finding out that another crew member suffers from the same problem, they used two sets of documentation of their state of vision while they were in space.

The ultrasound device found that the back of the eyeball was swollen and the optic nerve was curved. The results were confirmed on an MRI scan made on the eighth day after landing. After that, there were also cosmonauts who reported on vision changes after being in orbit.

“We still do not know what causes this problem,” said Sersk.

Among the reasons Sersk (not only the cosmonaut, but also the doctor) cites nutrition, an increase in carbon dioxide on board, which dilates blood vessels or an increase in intracranial pressure from the Advanced Resistive Exercise Device (ARED), which helps the crew to maintain shape. The device can produce up to 600 pounds of power, which is twice the capabilities of its predecessor IRED.

According to a new study, visual changes may be caused by volume changes in the clear fluid of the brain and spinal cord. On Earth, cerebrospinal fluid (CSF) is necessary for the transportation of nutrients and the removal of waste, despite the position of a person (lying, sitting, standing). But in space, you do not change. So says lead author Noam Alperin, a professor of radiology and biomedical engineering at Miller Medical School at the University of Miami.

Why astronauts vision deteriorates?

This 2012 image shows a change in the astronaut's right eye. You can see a fracture of the optic nerve, as well as flattening on the back of the eyeball (Radiological Society of North America).

“On Earth, CSF (cerebrospinal fluid) takes into account pressure changes, but the system is confused in space because of a lack of change in posture,” Alperin said in a statement.

Although research and innovative, but it refers to a small group of people (not so much flying into space). Astronauts on the ISS conducted 7 long missions, but the short-term (on the spacecraft) recites 9.

MRI was done to all astronauts before and after the flight. They also did an in-orbit scan. It was found that long flights cause large flattening in the eyeballs and more bulging of the optic nerve.

In addition, they found changes in the volume of CSF, both at the place of production in the brain and in the optic nerve inside the part of the skull that holds the eye. The research team says that countermeasures should be taken at the beginning of the mission to avoid irreparable damage.

Why astronauts vision deteriorates?

Canadian astronaut Bob Serk is one of the first astronauts to look at an eye problem during his last space flight in 2012. (NASA)

In early October, NASA issued a press release regarding intracranial pressure. When Scott Kelly and Mikhail Kornienko completed the one-year mission (2015-2016), their intracranial pressure was evaluated with devices for testing fluid pressure and sound waves produced in the inner ear. While the mission data is being analyzed, NASA says they have not found “pathologically significant increases” in intracranial pressure, but this can still be the cause of the visual impairment. The agency plans to address this issue in more detail on the space station using other methods (for example, ultrasound).

“There is an accumulation of cerebrospinal fluid in the space behind the eyes. But we still can not find the cause, ”- said Michael Stenger, responsible for visual impairment and intracranial pressure of the company KBRwyle. “Increased venous pressure or altered lymphatic drainage can isolate fluid behind the eye, thereby causing compartment syndrome.”

For his part, Sersk (he is retired) said that the issue must be resolved before sending a mission to Mars in the 2030s. Considering modern technologies, it will take months to travel in two directions. And the crew should feel comfortable. “If a journey of 6 months affects your eyesight, then what will happen in 2.5 years?”

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