Leonardo da Vinci may have had a form of strabismus, or eye misalignment, that helped him create masterpieces such as the Mona Lisa, Vitruvian Man, and Salvator Mundi, the author of a new study writes. The evidence suggests that da Vinci had intermittent exotropia, Christopher W. Tyler, PhD, DSc, writes in an article published online October 18 in JAMA Ophthalmology. With exotropia, one eye turns slightly outward, which may have enhanced the artist's ability to render 3-dimensional objects on a 2-dimensional surface, Tyler suggests. "This would perhaps explain his great facility for depicting the 3-dimensional solidity of faces and objects in the world and the distant depth recession of mountainous scenes." It is likely that other great artists, including Rembrandt van Rijn, Pablo Picasso, Edgar Degas, Giovanni Francesco Barbieri, and Albrecht Dürer, also had strabismus, as determined by studying their self-portraits, adds Tyler, a visual neuroscientist in the Division of Optometry and Vision Sciences, School of Health Sciences, City University of London, United Kingdom. Da Vinci, however, presented a more challenging case because few life portraits of him exist. Lacking definitive attributions of da Vinci's likeness, Tyler looked for evidence of strabismus in six "candidate images": two sculptures, two oil paintings, and two drawings. All are works for which da Vinci is thought either to have projected parts of his own appearance or served as a model. "Strabismus was assessed by fitting circles and ellipses to the pupils, irises, and eyelid apertures images identified as portraits of Leonardo da Vinci and measuring their relative positions," Tyler writes. Measurements from the six works yielded a mean optic axis angle estimate between the right and left eyes that was consistent with a diagnosis of intermittent exotropia (t5 =2.69; P = .04, 2-tailed), with a mean exodeviation of -10.3o. These findings suggest that da Vinci may have had an exotropic tendency of approximately -10.3o when relaxed, but could have reverted to orthotropia when concentrating on his work. With intermittent exotropia, da Vinci would have been able to switch from binocular to monocular vision at will, Tyler concludes. "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." Source
