Ocular accommodative changes in humans induced by positional changes with respect to gravity

Results are presented for an experimental study concerning ocular accommodation measurements in normal human subjects while they were rotated at a speed of 1 deg/sec about their naso-occipital axis. A few rotations were done about an interaural axis. It is shown that altering the head position with respect to gravity is followed by a change in ocular refraction, with the major change being in a lens-thickening or accommodative direction. Reasons for ascribing these changes to reflex changes in ocular accommodation are given. Arguments are presented relating this accommodative response to the utricles, which are nearly parallel to the earth horizontal.