(Telegraph) Leonardo da Vinci’s keen eye for art may have been due to vision problem
But new research has shown that an intermittent flaw in his eyesight may also have helped him to perfectly capture three-dimensional form.
Professor Christopher Tyler from City, University of London, studied two sculptures, two oil paintings and two drawings which are either self-portraits, or for which Leonardo posed as the model.
They included Leonardo’s own Salvator Mundi, Vitruvian Man and Andrea del Verrocchio’s bronze statue of David.
In each case, the alignments of the pupils in the eye apertures diverged by up to 13.2 degrees, suggesting that Leonardo had a form of strabismus known as exotropia, in which one eye looks directly at an object while the other gazes off to one side.
It is also known ‘stereo-blindness’, and it prevents people from combining independent images from each retina to create depth perception.
However the condition is thought to be hugely useful for artists, as it allows them to view the three-dimensional world in two dimensions, and so replicate it on paper for easier than people trying to do the same with a three dimensional view in front of them.
Writing in the journal Jama Opthalmology, Prof Tyler said: “The presence of exotropia, particularly if it was intermittent, may have contributed to da Vinci’s exceptional ability to capture space on the flat canvas.
“Intermittent exotropia is generally associated with good stereoscopic vision when the eyes are straight but allows for its elimination when exotropic, with suppression of awareness of the deviating eye.
“This condition is therefore rather convenient for the painter, since viewing the world with 1 eye allows direct comparison with the flat image being drawn or painted.”
Around one in 10 people is thought to be stereoblind and the condition is often so subtle that many people do not even realise they have it. They are often also dyslexic.
The condition usually starts in early childhood when the muscles which keep the two eyeballs aligned fail to develop properly. As one eye focuses on the scene in front the other drifts away and can lead to double vision until the brain gradually begins to suppress messages from the wandering eye.
The effect is similar to closing one eye, a technique used by many patiners in an attempt to see the world in two dimensions.
Recent studies have shown that a host of other well-known artists have the condition, including Rembrandt, Gustav Klimt, Man Ray, Winslow Homer, Willem De Kooning, Picasso, and Roy Lichtenstein.
Artists who are stereoblind are also thought to have a greater ability to focus on the shapes of objects and the ‘negative’ space around the objects, which gives them an advantage when depicting the three dimensional world as a flat image.