RAPID eye movement during dreams, thought to help the brain create vivid
images, may have evolved to prevent the eye suffocating behind a closed lid, a
physiologist in the US says.
To reach the cornea when the eyes are closed, oxygen from blood vessels near
the iris must cross a clear liquid called the aqueous humour. David Maurice of
Columbia University, New York, stained his aqueous humour with a fluorescent
dye. When he shut his eyes and kept them still, the stain stayed in a layer near
the surface, but when he moved his eyes back and forth, the dye mixed
rapidly.
Maurice suggests in this month’s Experimental Eye Research (vol 66,
p 139) that rapid eye movement evolved to keep fresh oxygen washing over the
cornea.
