Are astronauts going blind? Scientists uncover alarming eye health issues from space travel

Space travel has long been known to have profound effects on the human body. Most of these are well-documented, but one area that is increasingly coming under scrutiny is the effect of space travel on eye health. Scientists are particularly concerned about a condition called Spaceflight-Associated Neuro-ocular Syndrome, or SANS, which affects astronauts' vision. A Université de Montréal study found that 70% of astronauts experience eyesight changes while in space, which may cause serious risks, especially for long-term or deep-space missions like those to Mars.

In space, the mechanism of microgravity results in the displacement of bodily fluids, which, in Earth's gravitational environment, are more uniformly spread across the human body. This change leads the fluids to become pooled at the head, so that the internal pressure in their eyes is highly elevated. Fluid pressure in eyes is a direct contributor to seeing and vision without impairment. These researchers found considerable alterations in some aspects of their astronauts' vision:
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Ocular rigidity is the tightness of the eye. By 33%, the rigidity has reduced that the eye feels softer or a bit more malleable in nature, due to which more damage can happen to the eyes.

IOP stands for the pressure of fluid within the eye. A drop of 11% indicates a lessened pressure in the eye. This will change the way in which aqueous humor is circulated, potentially causing a disruption to the way by which nutrients reach the tissues and waste products are removed.

Ocular pulse amplitude is the variation in eye pressure with each heartbeat, related to the flow of blood through the eye. A 25% reduction would imply less variation in pressure with each heartbeat, indicating that perhaps the blood flow to the eye is reduced or not as efficient.
These caused blurring vision and, in some instances, swelling of the optic nerve. Ironically, in some astronauts' experience, a new eyeglass prescription became necessary after finishing their missions, owing to this changed vision.

While SANS symptoms are ominous, it is reassuring to know that in the vast majority of astronauts returning to Earth from space, they regained normal vision. In this group of 13 astronauts studied, about 80% exhibited some symptoms during their missions of impaired vision. The symptoms often abated spontaneously upon return to Earth. Finally, corrective lenses often helped in returning the astronaut's vision back to normal.
Nevertheless, the likelihood that these vision impairments may progress during long-duration spaceflights remains a threat. Longer space missions, for example to Mars, will put astronauts under microgravity conditions for even longer, which can make the effects of SANS more severe.

Researchers and space agencies, such as NASA, are working on ways to address and prevent these vision changes for future space missions. Some of the solutions being explored include:





In collaboration with NASA, researchers from Maisonneuve-Rosemont Hospital in Canada are focused on developing countermeasures to SANS before humanity embarks on longer space missions. If left untreated, the vision problems caused by SANS could endanger the safety of astronauts and hinder the success of critical missions, such as a crewed mission to Mars. With space exploration undergoing advanced evolution, it will definitely be crucial to understand and manage the challenges of SANS to ensure good health and safety for astronauts in future deep space missions.
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