"Da Vinci is believed to have had a condition called intermittent exotropia — commonly referred to as being 'walleyed' — a form of strabismus, eye misalignment..."

"... that affects about 4 percent of the U.S. population. Those with exotropia usually end up favoring one eye over the other, which means they are more likely to see the world as if it were, say, painted on a flat canvas. 'When they’re in that condition . . . they’re only seeing the world monocularly, with much reduced depth cues,' the study’s author, Christopher Tyler, a professor at City University of London and researcher at the Smith-Kettlewell Eye Research Institute in San Francisco, told The Washington Post. 'The image they’re seeing is much closer to what they want to paint on the canvas.' ... But in da Vinci’s case, the painter was, at times, able to control his wandering eye, which in turn provided him with an artistic advantage, Tyler said, noting that the ability to switch between the two perspectives meant that da Vinci would 'be very aware of the 3-D and 2-D depth cues and the difference between them.' Tyler, who has studied da Vinci’s life for more than 20 years, said he started noticing the disorder’s telltale sign while examining works by both the artist himself and those done of him. In many cases, 'they had the eyes diverted,' he said. 'This is something I would notice, what I’m attuned to notice,' said Tyler, who specializes in studying binocular vision.... Previous studies analyzing eye alignment in self-portraits have suggested that painters such as Rembrandt, Edgar Degas and Pablo Picasso were also strabismic."

From "Leonardo da Vinci’s genius may be rooted in a common eye disorder, new study says" (WaPo).

A Picasso self-portrait:



What has he done to his eyes? Perhaps less than it appears.