An eye disorder may have given Leonardo da Vinci an artistic edge

A neuroscientist offers evidence that the artist had exotropia, in which one eye turns outward

Salvator Mundi painting

EYE-OPENER  It’s believed that Leonardo da Vinci used his own likeness in his Salvator Mundi painting (shown). The artist may have had exotropia, a type of eye misalignment that causes one eye to turn slightly outward, a study finds.

Coldcreation/Wikimedia Commons

If Leonardo da Vinci had a good eye doctor, he might not have become such a great artist. At least that’s what an analysis of paintings and sculptures believed to be modeled after da Vinci suggests.

Visual neuroscientist Christopher Tyler of the City University of London examined six pieces of art, including Salvator Mundi and Vitruvian Man. Five of the pieces depict an eye misalignment consistent with a disorder called exotropia that can interfere with three-dimensional vision, Tyler reports online October 18 in JAMA Ophthalmology.

Exotropia, in which one eye turns slightly outward, is one of several eye disorders collectively called strabismus. Today, strabismus, which affects 4 percent of people in the United States, is treated with special glasses, eye patches or surgery.

Tyler calculated the differences in eye alignment using the same sorts of measurements that an optometrist does when tailoring a pair of glasses. Most of the portraits showed the eyes misaligned, but Vitruvian Man by da Vinci himself did not. As a result, da Vinci may have had intermittent exotropia, present only some of the time and perhaps controllable, Tyler suspects. “The person [with intermittent exotropia] can align their eyes and see in 3-D, but if they’re inattentive or tired, the eye may droop,” he says.

If da Vinci could control his exotropia, Tyler speculates that it would have been an artistic advantage. “The artist’s job is to paint on a 2-D surface,” he says. “This can be difficult when you view the world three-dimensionally.” Both eyes need to focus on the same subject for 3-D vision. Many artists shut one eye when viewing their subjects to more easily translate details into two dimensions. But with intermittent exotropia, da Vinci could have switched from 3-D to 2-D and back again with ease.

EYES OF THE BEHOLDER Leonardo da Vinci’s teacher, Andrea del Verrocchio, may have used da Vinci as a model for this sculpture of King David. The difference in the angles between the left and right pupils suggests the teacher captured da Vinci’s exotropia. C.W. Tyler/JAMA Ophthalmology 2018

Amanda B. Keener is a freelance science journalist based in Littleton, Colo.

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