Increased Intraocular Pressure in Glaucomatous, Ocular Hypertensive, and Normotensive Space Shuttle Crew.

BACKGROUND: Glaucoma and ocular hypertension (OHT) are prevalent diseases with baseline intraocular pressure (IOP) elevations that future astronauts and spaceflight participants may suffer from. Preflight, in-flight, and postflight IOP measurements were collected aboard two U.S. Space Shuttle Program missions in normotensive control, OHT, and glaucomatous crewmembers. METHODS: Five subjects (three controls, one glaucomatous, one OHT) were studied aboard 2-wk Space Shuttle missions. Baseline IOP (triplicate; handheld tonometry) was recorded during training 12 mo preflight, in flight (114 d), and postflight (329 d). Subjective symptoms were recorded via questionnaires. Data were analyzed using a spreadsheet with two-sample t-tests. P-value < 0.05 determined significance. RESULTS: IOP increased for all in-flight vs. preflight measurements for controls (N 3, 48.9, 16.9, 5.85), OHT (N 1, 20.3), and glaucomatous (N 1, 32.2) groups. IOP eventually returned to baseline postflight [Return (R)35 d], except for the astronaut with OHT (R917). Subjective symptoms, likely multifactorial, included blurredvision, decreased visual acuity, and headaches. DISCUSSION: IOP increased during spaceflight and normalized upon return. Astronauts and commercial spaceflight participants may need screening for elevated IOP to potentially prevent sequelae related to glaucoma and OHT, the former which requires treatment in flight and the latter which may need prophylaxis. Previous studies have shown elevated IOP upon entry into microgravity with various normalization timeframes in flight and postflight. It is unclear how increased IOP relates to spaceflight-associated neuro-ocular syndrome (SANS); however, several hypotheses exist. Treatment strategies should be available for acute and chronic ocular pathology during spaceflight despite the unique challenges of eye-drop application in microgravity. Dalal SR, Ramachandran V, Khalid R, Manuel FK, Knowles JR, Jones JA. Increased intraocular pressure in glaucomatous, ocular hypertensive, and normotensive space shuttle crew. Aerosp Med Hum Perform. 2021; 92(9):728733.

Space Radiation Protection Countermeasures in Microgravity and Planetary Exploration.

BACKGROUND: Space radiation is one of the principal environmental factors limiting the human tolerance for space travel, and therefore a primary risk in need of mitigation strategies to enable crewed exploration of the solar system. METHODS: We summarize the current state of knowledge regarding potential means to reduce the biological effects of space radiation. New countermeasure strategies for exploration-class missions are proposed, based on recent advances in nutrition, pharmacologic, and immune science. RESULTS: Radiation protection can be categorized into (1) exposure-limiting: shielding and mission duration; (2) countermeasures: radioprotectors, radiomodulators, radiomitigators, and immune-modulation, and; (3) treatment and supportive care for the effects of radiation. Vehicle and mission design can augment the overall exposure. Testing in terrestrial laboratories and earth-based exposure facilities, as well as on the International Space Station (ISS), has demonstrated that dietary and pharmacologic countermeasures can be safe and effective. Immune system modulators are less robustly tested but show promise. Therapies for radiation prodromal syndrome may include pharmacologic agents; and autologous marrow for acute radiation syndrome (ARS). CONCLUSIONS: Current radiation protection technology is not yet optimized, but nevertheless offers substantial protection to crews based on Lunar or Mars design reference missions. With additional research and human testing, the space radiation risk can be further mitigated to allow for long-duration exploration of the solar system.