Ocular health in outer space and beyond gravity: A minireview

Area of Science:

• Ophthalmology
• Aerospace Medicine
• Neuroscience

Background:

• Prolonged microgravity exposure alters astronaut ocular physiology, causing spaceflight-associated neuro-ocular syndrome (SANS).
• SANS affects roughly one-third of astronauts on missions longer than six months.
• Key SANS features include optic disc edema, globe flattening, and hyperopic shifts.

Purpose of the Study:

• To review current evidence on ocular adaptations to spaceflight.
• To explore SANS pathophysiology, diagnostics, and countermeasures.
• To integrate findings from peer-reviewed literature and space agency reports.

Main Methods:

• Systematic literature review (2000-2025) across PubMed, Scopus, and Web of Science.
• Inclusion of peer-reviewed studies and technical reports from NASA and ESA.
• Synthesis of data on ocular changes, mechanisms, and interventions.

Main Results:

• Ocular changes consistent with SANS are prevalent in long-duration spaceflight.
• Cephalad fluid shifts, altered CSF dynamics, and impaired glymphatic flow contribute to SANS.
• Microgravity also increases risks for dry eye disease, infections, and radiation-induced cataracts.

Conclusions:

• Early SANS detection is improving with advanced in-flight imaging technologies.
• Countermeasures like lower body negative pressure and artificial gravity show promise.
• Understanding spaceflight ocular adaptations benefits both mission safety and terrestrial neuro-ophthalmic research.