The Effect of Microgravity on Ocular Structures and Visual Function: A Review

Ergonomic Challenges for Astronauts during Space Travel and the Need for Space Medicine

“…The planet is rocky, has a magnetic field and an axial tilt which may provide seasonal variations in climatic conditions. Now in 2017, as we comprehend taking our first steps towards space travel within the solar system which are designed to lead to lunar or planetary colonization within the next [10][11][12][13][14][15][16][17][18][19][20] years, what will we need to know and to develop which will allow such a crew to be safely maintained for these first steps and which may ultimately provide a foundation to permit travel to and permanent colonization of a new world?…”

Microgravity-induced ocular changes in astronauts: a sight odyssey

“…In addition to space radiation-induced cataract, the effects of microgravity on the eyes are considered the most impactful health problems for the success of long-term space travels. Still, a minimal comparison can be obtained by the experiences on high-altitude climbing, which have also shown harmful consequences to the retina, optic nerve, and cornea (mainly related to corneal refractive surgeries) (3)(4)(5) . As an analogy to the importance of vision-threatening environmental scenarios, the book "Into thin air" authored by Jon Krakauer quotes high-altitude-related blurred vision resulting in a Mount Everest tragedy as the critical limitation to an adventurer (6) .…”

“…As an analogy to the importance of vision-threatening environmental scenarios, the book "Into thin air" authored by Jon Krakauer quotes high-altitude-related blurred vision resulting in a Mount Everest tragedy as the critical limitation to an adventurer (6) . The first ocular findings in space flights were related to the blurring of vision, described in the 60's and later were associated with the Visual Impairment and Intracranial Pressure (VIIP) syndrome (3,7) . The findings outlined in this syndrome could be explained by modifications in the fluid shift pattern resulting from altered pressures in several liquid compartments of the body, especially the intraocular pressure (IOP), the intracranial pressure (ICP) and the blood pressure.…”

“…Thus, the neuroretinal-cerebrospinal fluid interface (including lamina cribrosa) could be affected by microgravity, due to the local "cul-de-sac" anatomy of the optic nerve head and the relative increased ICP transmitted to the eye by the subarachnoid space. As consequence, the optic nerve sheath distension, optic disc edema, vascular changes in the choroid and retina (eg., folds choroidal, thickening of the retinal fiber layer, cotton wool spots), "flattening" of the eyeball and a hyperopic shift have been described in several astronauts (3,8) . Still, a moderate acute IOP increase in the first moments in microgravity (probably due to congestion in the episcleral veins), followed by a steady IOP decrease were observed during longer periods under microgravity and in the post-flight evaluations (8,9) .…”

“…Given the difficulties and cost of space travel, parabolic flight tests (producing transient periods of microgravity) and the head-down bed-rest studies (simulating the pressure effects of microgravity) has been used to examine several systemic and ocular changes (3) . In addition to space radiation-induced cataract, the effects of microgravity on the eyes are considered the most impactful health problems for the success of long-term space travels.…”