Ocular conditions and injuries, detection and management in spaceflight

**Background:** Ocular trauma and conditions in spaceflight have historically been considered lower risk compared to other medical events, but future missions to the Moon and Mars will involve increased construction-type work, longer durations, and exposure to celestial dust, raising the risk of ocular injury. The NASA Critical Path Roadmap Project identified trauma as the highest level of risk, and the In-Flight Medical Risk is currently held at 'Red' for long-duration lunar missions. Space Flight-Associated Neuro-Ocular Syndrome (SANS) is well-studied, but other ocular conditions such as corneal abrasions, chemical burns, infections, lens dislocation, globe disruption, retinal detachment, and vascular occlusions also pose significant threats to crew health and mission success. This review aims to characterize potential ocular injuries, review the literature, and discuss diagnostic and treatment modalities available and under consideration for spaceflight.

**Methods:** A systematic literature review was conducted using PubMed and Google Scholar with search terms including 'ocular injuries,' 'trauma,' 'eye,' 'spaceflight,' 'astronaut,' 'microgravity,' and 'technology.' Non-human studies, non-English texts, and conference abstracts were excluded. Literature on SANS was excluded to focus on lesser-reviewed ocular conditions. Additionally, a comprehensive review of NASA evidence books, including those on artificial gravity, celestial dust exposure, and inflight medical conditions, was performed. Data on medical conditions and symptomatology were obtained from the Lifetime Surveillance of Astronaut Health (LSAH) records for US astronauts during the Space Shuttle Program and ISS through Expedition 13 in 2006.

**Key Results:** The LSAH records show that the most common ocular event was eye abrasion (foreign body) with 70 events, followed by eye abnormality unspecified (9 events), eye chemical burn (6 events), eye infection (5 events), eye irritation (5 events), eye debris (4 events), dry eyes (4 events), and puffy eyes (1 event). Corneal abrasions are often caused by foreign bodies, including celestial dust, which has sharp edges and is particularly abrasive. Lunar dust studies in rabbits showed only minimal irritation (slight redness and swelling at 1 hour) with no corneal abrasions on fluorescein staining at 24, 48, and 72 hours. However, chronic exposure to lunar dust at levels as low as 20 mg/m³ elicits molecular responses in corneal tissue, including oxidative stress, mitochondrial dysfunction, and fibrosis. Risk factors for corneal infection and ulcers include contact lens wear, trauma, immune dysregulation, and corneal edema, all of which are present in spaceflight. Lens dislocation is rare but could be exacerbated by globe flattening and changes in suspensory ligaments. Globe disruption has not been reported but is a concern given 70 foreign body events. Retinal detachment risk may be increased by oxidative stress and pressure stressors. The first case of deep venous thrombosis in spaceflight was recently reported, highlighting hypercoagulability risk for retinal vascular occlusions. Chemical burns are a leading cause of potential evacuation, with eye chemical burn being the top influential condition for certain ISS missions. Radiation exposure, especially beyond LEO, increases cataract risk and other ocular damage. Current diagnostic modalities on ISS include vision questionnaires, visual acuity testing, Amsler grid, fundoscopy, orbital ultrasound, and OCT. Ultrasound can assess lens position and large vitreous abnormalities but is limited for anterior surface evaluation. OCT has been used to evaluate anterior segment pathologies like corneal abrasions and ulcers with remote guidance. Treatment modalities include artificial tears, proparacaine, fluorescein strips, ciprofloxacin, polytrim, cyclopentolate, and vidarabine. For chemical burns, irrigation with drink bags and goggles is used, but pH assessment is not currently performed. Protective measures include goggles, fish oil supplements, collagen corneal shields, and preservative-free artificial tears.

**Clinical Implications:** The shift from Earth-tethered to Earth-independent medical management for lunar and Mars missions requires autonomous diagnostic and treatment capabilities due to communication delays and limited evacuation options. Current ISS capabilities are inadequate for time-sensitive ocular injuries. The review highlights the need for improved anterior segment diagnostic tools, such as handheld portable slit lamps and anterior segment cameras, and the integration of artificial intelligence for asynchronous diagnostics. Preventive measures, including routine fluorescein exams and preservative-free artificial tears, could reduce the incidence and severity of ocular conditions. A holistic team approach between NASA and the ophthalmology community is essential to improve ocular health in spaceflight and ensure mission success.