Everyone knows hindsight is twenty-twenty.

But what about “blindsight”… the ability to sense objects or obstacles even though the parts of the brain that allow us to form pictures have been damaged?

This happens to people whose visual lobes… located toward the back of the skull on each side of the head… have been destroyed by strokes or injuries.

Such people cannot “see” in any conventional sense.

Yet, they somehow sense things using the brain’s primitive, and entirely subconscious, visual system.

In an example from an international team of brain researchers reported in The New York Times, a man who had been blinded by strokes was able to navigate a cluttered hallway.

He thought the experiment was a waste of time. But he amazed himself by sidestepping a garbage can, a tripod, a stack of paper and several boxes.

The demonstration was originally detailed in the journal Current Biology in the first study to prove “blindsight” in someone completely lacking the brain’s normal visual processing region.

Profoundly blind by any normal measure… his eyes were healthy, but scans revealed no activity in the volunteer’s visual cortex… the man must have relied on other areas of his brain to make use of information he was receiving through his eyes.

Scientists hope that with practice, people with brain injuries may learn to rely on these subconscious systems.

They will never achieve “twenty-twenty” quality vision.

But they might learn to navigate through a crowded room.