Experiment Type
Research Areas
Neurophysiology
Clinical medicine
Species Studied
Homo sapiens
(Human)
OBJECTIVES:
Both American and Soviet astronauts have reported conflicting experiences with visual capability in space. While some astronauts report considerable increases in visual capability, some report marked decreases in capability, and still others report no change.
Since weightlessness causes disruption of the
vestibular-ocular system and a redistribution of fluid throughout the body which could cause
cerebral edema and changes in eyeball shape, changes in visual capability would not be
unexpected. Studies using two different testing methods, near visual acuity and contrast sensitivity, were undertaken to determine the
effects of weightlessness on vision. Near visual acuity was selected to determine changes in
accommodation and other possible changes affecting vision. Contrast sensitivity testing was
selected as a more precise measure of general vision loss as well as an aid in determining the possible physiological location and nature of
vision changes. Evidence shows that significant losses in contrast sensitivity can occur with little or no effect on visual acuity.