“There was his sensitivity to human character, his grasp of light and shade, his virtuoso hand with a brush. But Rembrandt’s self-portraits reveal another characteristic that may have contributed to his genius: a walleye.
Having studied 36 of those rather unforgiving self-portraits, a neuroscientist suggests that Rembrandt was stereoblind – that is, because his eyes did not align correctly, his brain automatically used one eye for many visual tasks. This may have allowed him to flatten images automatically as he observed the world, and then transfer that perspective onto the two-dimensional canvas, says Margaret S. Livingstone, a professor of neurobiology at Harvard Medical School.”
More here from the New York Times.