Neurostimulation as a technology countermeasure for dry eye syndrome in astronauts

Dry eye syndrome (DES) poses a significant challenge for astronauts during space missions, with reports indicating up to 30% of International Space Station (ISS) crew members. The microgravity environment of space alters fluid dynamics, affecting distribution of fluids on the surface of the eye as well as inducing cephalad fluid shifts that can alter tear drainage. Chronic and persistent DES not only impairs visual function, but also compromises the removal of debris, a heightened risk for corneal abrasions in the microgravity environment. Despite the availability of artificial tears on the ISS, the efficacy is challenged by altered fluid dynamics within the bottle and risks of contamination, thereby exacerbating the potential for corneal abrasions. In light of these challenges, there is a pressing need for innovative approaches to address DES in astronauts. Neurostimulation has emerged as a promising technology countermeasure for DES in spaceflight. By leveraging electrical signals to modulate neural function, neurostimulation offers a novel therapeutic avenue for managing DES symptoms. In this paper, we will explore the risk factors and current treatment modalities for DES, highlighting the limitations of existing approaches. Furthermore, we will delve into the novelty and potential of neurostimulation as a countermeasure for DES in future long-duration missions, including those to the Moon and Mars.