Astronauts who have been in space for more than 6 months have been diagnosed with eye problems

Santiago Constantino, an ophthalmologist at the University of Montreal, has discovered that after 6-12 months aboard the International Space Station (ISS), astronauts develop eye problems. The scientist gathered a group of researchers to identify the biomechanical changes responsible for this.

According to a study published in the IEEE Journal of Engineering in Medicine and Biology, at least 70% of astronauts on the ISS suffered from spaceflight-related neuroocular syndrome, or SANS. This is due to the low level of gravity (microgravity) in space, Phys Org writes.

During the study, the researchers analyzed data collected by the Canadian NASA team on 13 astronauts who spent 157 to 186 days on the ISS.

The researchers compared three ocular parameters before and after astronaut space missions: corneal stiffness, intraocular pressure, and eye pulse amplitude. As a result, they saw significant changes in the biomechanical properties of the astronauts' eyes: a 33% decrease in eyeball stiffness, an 11% decrease in intraocular pressure, and a 25% decrease in eye pulse amplitude. These changes were accompanied by symptoms such as a decrease in eye size, a change in the focal field, and some cases, optic nerve swelling and retinal folds. Scientists also found that five astronauts had choroidal thicknesses of more than 400 micrometers, which did not correlate with age, gender, or previous experience in space.

"Weightlessness alters the distribution of blood in the body, increasing blood flow to the head and slowing venous circulation in the eye. This is likely to cause an expansion of the choroid, the vascular layer that feeds the retina," the ophthalmologist commented on the study results.

In addition, according to the researchers, blood pulsations in microgravity can create a water hammer effect, in which sudden changes in blood flow pressure cause a mechanical shock to the eye, leading to significant tissue remodeling.

However, according to scientists, after returning to Earth, the condition of the eyes normalizes after some time. According to them, wearing corrective glasses, in most cases, was sufficient to eliminate the symptoms that arose on board the ISS.

However, scientists are continuing their research and are cautiously assessing how vision might be affected by long-duration missions such as a flight to Mars. After all, the effects of prolonged exposure to microgravity on eye health remain unknown, and there are currently no preventive or palliative measures.

"The detected changes in the mechanical properties of the eye can serve as biomarkers for predicting the development of SANS (spaceflight-related neuroocular syndrome). This will help to identify astronauts at risk before they develop serious eye problems during long-term missions," Costantino said.

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