Even if you are not aware of everything you take in, your eyes are sending visual information to your brain.  This unconscious seeing is evidenced in a phenomenon called "blindsight", where people have no awareness, but their brains can see - even in subjects with visual impairment, caused by damage to a part of the brain called the visual cortex. 

It has long been known that some patients with damage in the visual cortex, who cannot see, can still walk and avoid obstacles but that  was nor proof they were using blindsight. A new study demonstrated that blindsight in monkeys is present - and in ordinary environments, not a controlled laboratory. 

The researchers previously showed blindsight in monkeys with damage in the visual area of the brain. They were able to turn their eyes to 'unseen' visual stimuli. But that was under specific laboratory conditions. For the new work they recorded eye movements of monkeys freely watching video clips of everyday life scenes. They found that the monkeys were able to turn their eyes to the prominent portions of videos in term of motion, brightness or color. By looking at the eye movements of the monkeys with visual disability, they could determine what they pay attention to, although they do not see. Blindsight.

Assistant Professor Masatoshi Yoshida, from The National Institute for Physiological Sciences in Japan said, "This new finding indicates that blindsight can be used in everyday life of patients with hemianopia by cerebrovascular disorder. Then, there is the possibility that patients with visual impairment can recover their hidden visual function by rehabilitation." He also said "measurement of eye movements during viewing movie clips can be an efficient method to examine how well the patients can see unconsciously."

Published in Current Biology.