## 1 Introduction  
Human spaceflight offers an unparalleled opportunity to investigate the nature of life and biological systems in environments that cannot be replicated on Earth. Space-basedresearch facilitates controlled studies in microgravity and radiation exposure, yielding insights into musculoskeletal degeneration, immune modulation, wound healing, and stem cell behavior--core concerns in space biology and space medicine [1; 2; 3]. These experiments are more than clinical curiosities; they inform new models of human physiology, offer therapeutic insights for Earth-based medicine, and contribute to a growing understanding of how life adapts to extreme environments [2]. These insights contribute to a broader scientific imperative: understanding life's potential and persistence beyond Earth. Astrobiology--defined by the National Aeronautics and Space Administration (NASA) as the study of the origin, evolution, distribution, and future of life in the universe--sits at the intersection of biology, chemistry, planetary science, and astronomy [4]. As missions to Mars, Europa, and beyond seek biosignatures and signs of past or present habitability, astronauts serve as uniquely capable field scientists. Their adaptability, contextual reasoning, and ability to perform in situ analysis make human-led exploration essential to answering the foundational questions of astrobiology: _Where did we come from? Are we alone? Where are we going?_[4; 5]. The success of this endeavor depends not only on engineering or propulsion--but on preserving human health, function, and perception in extreme environments. As spaceflight transitions from short-duration missions in low Earth orbit to prolonged planetary exploration, the physiological challenges faced by astronauts will intensify [6]. Missions to Mars or deep-space outposts will expose crews to months or years of microgravity, heightened radiation, and limited medical support [7]. These conditions amplify the consequences of even minor physiological disruptions. In this context, safeguarding physiological and sensory systems is vital not only for performance, but for survival. Identifying and mitigating these biomedical risks is a prerequisite for enabling the next era of human exploration beyond Earth orbit. Among these physiological systems, vision is paramount. Humanity's pursuit of space exploration continually pushes the limits of human endurance, exposing astronauts to extreme conditions that challenge even the most resilient organ systems, including the eye. The cornea, which provides over two-thirds of the eye's refractive power, is particularly vulnerable in microgravity, where precise vision is essential for mission success [8]. Even minor damage, such as a corneal abrasion from floating debris, can impact visual acuity and impair depth perception, jeopardizing vital tasks like extravehicular activities (EVAs). Similarly, visual distortions caused by stromal swelling or scarring can hinder key operations, from monitoring spacecraft systems to analyzing scientific data [9]. Ocular health in space is threatened by unique environmental stressors, including microgravity-induced fluid shifts, cosmic radiation, and confined living conditions, which increase the risk of corneal injury and visual impairment [8; 9]. Spaceflight Associated Neuro-Ocular Syndrome (SANS), characterized by optic disc edema and posterior segment changes, has also been linked to fluid shifts that could potentially contribute to corneal edema and dry eye symptoms, representing a possible anterior segment vulnerability [9; 10; 11]. Looking beyond SANS, astronauts are also at increased risk for corneal anomalies to include abrasions, infections, and radiation-induced damage, emphasizing the urgent need for innovative protective strategies [10; 12].