Also, check this article that I found on the web:
"Rembrandt, the 17th-century Dutch master known for his skill in using
light to carry perspective, may have been wall-eyed, a U.S. researcher
proposed on Wednesday. An analysis of 36 self-portraits of the great
painter suggest he had a strabismus -- a misalignment of one eye that
caused it to point slightly outward. This condition, popularly known
as wall-eye, may have given Rembrandt van Rijn an advantage in
translating three-dimensional scenes into two-dimensional paintings,
said Margaret Livingstone, a Harvard Medical School neurobiologist."
See more here: http://newsfromrussia.com/science/2004/09/16/56108.html