According to Researchers, they defined the cluster of “novel and unique physiologic and pathologic systemic and neuro-ocular responses recognized in astronauts during and after long-duration space flight,” known as space flight-associated neuro-ocular syndrome (SANS). Astronauts experiences the changes to the visual system that raise concerns about the possibility of vision loss during future manned missions to Mars or other destinations. This was published in JAMA Ophthalmology.
Astronauts experiencing changes in visual acuity while aboard the space station use adjustable eyeglasses to treat the problem. When they return to Earth, changes in visual acuity tend to regress back to the individual’s original refraction. Astronauts undergo various imaging studies, including pre- and post-mission intraorbital and intracranial magnetic resonance imaging (MRI) and pre-flight, in-flight, and post-flight studies using ultrasound and ocular coherence tomography.
The syndrome shares some similarities with terrestrial idiopathic intracranial hypertension (IIH), a condition characterized by increased cerebrospinal fluid (CSF) pressure within the spaces around the brain and spinal cord. But astronauts lacked typical IIH symptoms (such as chronic headache and tinnitus in sync with the pulse), and none had risk factors typical of IIH (such as obesity or use of drugs that can raise intracranial pressure). There were also other dissimilarities, such as the typically unilateral or asymmetric optic disc swelling of SANS vs. bilateral and symmetric swelling in IIH.
Dr. Lee said, “There could be fluid in your head and fluid in your orbit and optic nerve sheath, and we haven’t been able to adjudicate this question because we don’t have a spinal tap in space.”
Future studies will include studying astronauts who spend longer periods on the ISS, Dr. Lee said, and trying to find “terrestrial analogs on Earth,” such as head-down studies, that can mimic what scientists have observed in terms of the cephalad fluid shift.
“Understanding and possibly treating SANS with specific preflight, in-flight, and post-flight countermeasures may be necessary as the United States prepares for even longer-duration space flight missions,” the authors noted.
“The clinical implications of SANS for long-term space flight are enormous: astronauts need to be able to see in space,” Dr. John Berdahl, clinical spokesperson for the American Academy of Ophthalmology, told Reuters Health by email. “Given the stated goals of NASA and SpaceX to send humans to Mars, protecting vision during space flight must be a top priority.”
Dr. Lee said that he hopes the special communication in JAMA Ophthalmology helps brings greater awareness of SANS not only to ophthalmologists but also scientists in other fields, who might have ideas about interesting ways to approach the problem. We’re open to any ideas and hypotheses that might be generated that we can test.