How does space travel affect eye health?

As space travel becomes more frequent, it is vital to consider the effects of space flight and altered gravity on human health.

Researchers at Texas A&M University, led by Dr. Ana Diaz Artiles, are focusing on the impact of microgravity conditions on human eye health. 

Space travel and eye health 

According to the scientists, fluid shifts caused by microgravity can affect the cardiovascular system, including eye vessels. 

Spaceflight-Associated Neuro-ocular Syndrome

The microgravity changes can potentially lead to vision impairment, often referred to as Spaceflight-Associated Neuro-ocular Syndrome (SANS). This condition primarily affects astronauts who spend extended periods in microgravity environments.

SANS occurs when the fluid shifts associated with space travel increase pressure inside the skull and on the eyes, leading to changes in the shape of the eye and ocular perfusion pressure (OPP). 

Symptoms of SANS

Common symptoms include swelling of the optic disc, flattening of the back of the eye (globe flattening), and changes in the retina. These changes can result in blurred vision, difficulties in focusing on near objects, and other visual distortions.

Mechanisms and countermeasures

The exact mechanisms behind SANS are still being studied, but it is clear that the prolonged exposure to microgravity plays a significant role. 

Countermeasures such as special exercises, medications, and equipment like lower body negative pressure devices are being explored to mitigate these effects and protect astronauts’ vision during long-duration space missions.

Fluid shifts during space flight

“When we experience microgravity conditions, we see changes in the cardiovascular system because gravity is not pulling down all these fluids as it typically does on Earth when we are in an upright position,” said Dr. Diaz Artiles, an assistant professor in the Department of Aerospace Engineering. 

“When we’re upright, a large part of our fluids are stored in our legs, but in microgravity, we get a redistribution of fluids into the upper body.”

Mitigating headward fluid shifts 

Dr. Diaz Artiles’ team is exploring countermeasures like lower body negative pressure (LBNP) to mitigate headward fluid shifts. 

The recent study found that while lower body negative pressure effectively moves fluids to the lower body, it does not reduce ocular perfusion pressure, suggesting it may not be an effective countermeasure for Spaceflight Associated Neuro-ocular Syndrome. 

Further research is needed to fully understand the relationship between ocular perfusion pressure and SANS.

“This research is just one experiment of a three-part study to better understand the effects of fluid shift in the body and its relationship to SANS,” said Dr. Diaz Artiles.  

“Previous experiments in this study included the use of a tilt table for researchers to understand the cardiovascular effects of fluid shifts at different altered gravity levels, recreated by using different tilt angles.”

Future research on space travel

Upcoming research will also aim to conduct experiments in true microgravity conditions, such as parabolic flights, to better understand the impact of space travel on the human body. This comprehensive approach aims to develop effective countermeasures for the health challenges posed by altered gravity environments in space.

“Concern over the accuracy of terrestrial LBNP experiments should be considered, as the combination of reduced central venous pressure while still experiencing G_x (front-to-back) gravity conditions may produce results not necessarily comparable to physiological responses during spaceflight conditions. Thus, future studies should investigate LBNP responses in true microgravity conditions,” noted the researchers.

Space travel and human health

Space travel significantly impacts the human body in various ways. The microgravity environment leads to muscle atrophy and bone density loss because the body doesn’t have to support its weight. 

Astronauts often experience fluid redistribution, causing puffy faces and thinner legs, as well as changes in cardiovascular function due to the shift of fluids toward the upper body. Vision can be affected, sometimes resulting in long-term impairment. 

Additionally, space radiation poses a risk for increased cancer rates and potential damage to the nervous system. The psychological effects of isolation and confinement in space also present challenges, potentially leading to stress, sleep disorders, and other mental health issues. 

Overall, the human body undergoes significant physiological and psychological stress during space travel, requiring extensive countermeasures and research to mitigate these effects.

The study is published in the journal NPJ Microgravity.

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