This experiment was performed on nine Shuttle flights; 32 of 36 requested subjects were obtained. Near vision acuity data were analyzed for differences in the near point of accommodation among the preflight, in flight, postflight, and average of pre- and postflight measurements. Paired t-tests and analysis of variance with repeated measurements showed that no significant differences in diopter measurements existed among the three phases of flight. Contrast sensitivity data were analyzed for differences between the average preflight contrast sensitivity data and those obtained in flight, at landing, and postflight. Statistically significant individual differences in contrast sensitivity changes in space were found. Crewmembers exhibited different magnitudes of change at different spatial frequencies.
No clinically significant changes in near vision acuity in the microgravity environment of space were found during space shuttle flights. However, changes in contrast sensitivity were seen under these conditions. Alterations in contrast sensitivity occurring in the low and middle but not the high spatial frequencies cannot be readily attributed to changes in accommodation, but reflect more central effects. In general, the changes in contrast sensitivity are less than a factor of two and would not be expected to cause major visual performance increases or decreases. The possible physiological reasons for the changes in contrast sensitivity during space flight will require further research.
|Mission||Launch/Start Date||Landing/End Date||Duration|