Your vision is terrible--you just don't know it. A camera took the top picture. Laurent Itti, a postgraduate researcher in Caltech's Computation and Neural Systems Program, then computer-altered the photo to show the corresponding image that forms inside the eye, at the bottom. Light-detecting cells in the retina are tightly packed only in a small central region. The density of those cells decreases toward the outer edges of the retina, so peripheral vision becomes less crisp. And the location where the optic nerve meets the retina creates a perpetual blind spot. "We move our eyes three to five times per second, and we remember the objects we've just seen, so we think we see better than we actually do," says Itti.
Courtesy: James l. Amos/Corbis