Produced by: Mohsin Shaikh
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Astronauts aboard the ISS have reported unexpected visual shifts, with optic nerves swelling and eye shapes flattening. The changes, attributed to fluid shifts in microgravity, have left space agencies scrambling for solutions to preserve astronaut sight.
SANS causes increased pressure in the brain and eyes, leading to optic nerve swelling. This condition, first noticed in Russian cosmonauts, remained a mystery until NASA formally classified it in 2011 as a distinct neuro-ocular syndrome.
A critical symptom of SANS is the eye’s structural change, where the back of the eyeball flattens. This distorts vision and may pose severe risks on deep-space missions, such as those to Mars, where astronauts won’t have quick access to medical care.
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Ocular pressure fluctuates in microgravity, compressing the eye and affecting vision. A study by Santiago Costantino at Université de Montréal found a 33% drop in ocular rigidity and an 11% decline in intraocular pressure among ISS astronauts.
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Some astronauts experience shrinking visual fields, making it harder to focus on distant objects. This change is linked to altered blood flow in the eye, reducing its ability to maintain shape and function normally in prolonged microgravity.
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Many astronauts return to Earth with worsened vision, often developing farsightedness. Although some regain normal sight, others require corrective lenses, raising concerns about whether future missions could lead to permanent ocular damage.
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No one knows how long the human eye can endure microgravity before permanent damage occurs. Scientists fear that Mars-bound astronauts, who will spend years in space, could experience vision loss that may never fully recover.
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Current countermeasures are limited to temporary solutions, such as wearing specialized glasses. Researchers are testing negative pressure devices to pull fluids away from the head, but no definitive cure for SANS has been found.
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Without a breakthrough treatment, long-duration space travel remains at risk. If vision impairment worsens over time, Mars astronauts could arrive with critically reduced sight, making it dangerous to operate spacecraft or explore the surface.