Eye-brain axis in microgravity and its implications for Spaceflight Associated Neuro-ocular Syndrome

Abstract

Long-duration human spaceflight can lead to changes in both the eye and the brain, which have been referred to as Spaceflight Associated Neuro-ocular Syndrome (SANS). These changes may manifest as a constellation of symptoms, which can include optic disc edema, optic nerve sheath distension, choroidal folds, globe flattening, hyperopic shift, and cotton wool spots. Although the underpinning mechanisms for SANS are not yet known, contributors may include intracranial interstitial fluid accumulation following microgravity induced headward fluid shift. Development and validation of SANS countermeasures contribute to our understanding of etiology and accelerate new technology including exercise modalities, Lower Body Negative Pressure suits, venous thigh cuffs, and Impedance Threshold Devices. However, significant knowledge gaps remain including biomarkers, a full set of countermeasures and/or treatment regimes, and finally reliable ground based analogs to accelerate the research. This review from the European Space Agency SANS expert group summarizes past research and current knowledge on SANS, potential countermeasures, and key knowledge gaps, to further our understanding, prevention, and treatment of SANS both during human spaceflight and future extraterrestrial surface exploration.

Intraocular Pressure during Spaceflight and Risk of Glaucomatous Damage in Prolonged Microgravity

“…The use of swimming goggles has been found to cause a brief rise in intraocular pressure and translaminar pressure gradient as a result of the pressure exerted on the eyes [39]. Similarly, exposure to microgravity during spaceflight has been observed to induce alterations in the eye-brain axis and intracranial pressure [33,47,48]. Both situations present ocular concerns, as increased intraocular pressure may potentially increase the risk of glaucoma in both swimming goggles and microgravity environments [38,47].…”