The hypercapnic environment on the International Space Station (ISS): A potential contributing factor to ocular surface symptoms in astronauts.

With increasing advancements and efforts towards space exploration, there is a pressing need to understand the impacts of spaceflight on astronauts' health. Astronauts have reported signs and symptoms of dry eye disease upon traveling to the International Space Station (ISS), thus necessitating an evaluation of the factors that contribute to the onset of spaceflight associated dry eye disease. Prior literature describes the hypercapnic environment of the ISS; however, the link between the high CO2 levels and astronauts' symptoms of dry eye disease remains unexplored. Due to the terrestrial relationship between a hypertonic environment and ocular irritation as well as the terrestrial association between CO2 exposure and subsequent corneal acidosis, there is a strong necessity to investigate the relationship between the elevated CO2 levels in the closed environment of the ISS and astronauts' risk for dry eye disease development.