Microgravity-induced ocular changes are related to body weight.

Area of Science:

• Space Medicine
• Ophthalmology
• Human Physiology

Background:

• Tissue weight on Earth creates compressive forces, absent in microgravity.
• Microgravity may disproportionately affect heavier individuals.
• Spaceflight-associated neuroocular syndrome (SANS) involves ocular changes like globe flattening and optic disk edema.

Purpose of the Study:

• To investigate the relationship between astronaut preflight body weight and anthropometric measures with microgravity-induced ocular changes.
• To determine if higher body weight is a risk factor for developing SANS.

Main Methods:

• Analysis of pre- and postflight ocular measurements (disk edema, choroidal folds, refraction) from 45 long-duration astronauts.
• Comparison of anthropometric data (weight, chest/waist circumference) between astronauts who developed ocular changes and those who did not.
• Statistical analysis to assess the correlation between weight quartiles and the incidence of SANS indicators.

Main Results:

• Astronauts who developed new choroidal folds or optic disk edema had significantly higher mean preflight weights compared to those who did not.
• Increased chest and waist circumferences were also associated with developing ocular changes.
• The odds of developing optic disk edema or choroidal folds were substantially higher in the highest weight quartile (55%) versus the lowest (9%).
• No women in the cohort developed optic disk edema or choroidal folds, correlating with their significantly lower average body weight compared to men.

Conclusions:

• Preflight body weight and other anthropometric factors appear to be significant predictors of microgravity-induced ocular changes, including SANS.
• Heavier astronauts may be at a greater risk for developing vision-altering conditions during spaceflight.
• Further research is warranted to elucidate the mechanisms and confirm these findings in larger cohorts.