Deep Space Blind

Ever wanted to see the Earth from space? If so, you’d better have your specs handy. According to NASA and the International Space Station, approximately 40–60 percent of astronauts develop spaceflight-associated neuro-ocular syndrome (SANS) during their time away from Earth. Upon their return, these astronauts present with altered visual acuity, retinal injuries, globe flattening, optic disc edema, and mildly elevated intracranial pressure. The symptoms’ severity appears to correlate with time spent in space, resulting in recovery that can take years, if it’s reached at all (1).

Aiming to identify the causative mechanisms in SANS onset and progression, researchers from the Medical University of South Carolina used magnetic resonance venography to assess differences in the intracranial venous systems of a group of astronauts pre- and post-flight (2). They found that astronauts with SANS displayed significant increases in intracranial dural venous structural volumes upon returning to Earth compared with their non-SANS counterparts.

Unlike most veins, dural sinuses usually resist stretch and change – but venous sinus laxity appears to be a risk factor for SANS. This led the team to hypothesize that SANS occurs when the loss of gravitational hydrostatic pressure causes upward movement of lower body fluids and lack of drainage, leading to venous congestion in the head and neck. This, in turn, increases ICP and causes optic disc edema.

Understandably, these results come from a small group of astronauts and require confirmation in a larger population. The researchers are currently planning further studies, including investigations into gender-related SANS differences and even conducting MRI scans in space. The condition, one of NASA’s highest research priorities, presents a major roadblock to large-scale space colonization. After all, if we want to traverse the far corners of the galaxy, we need to be able to see where we’re going!