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Evidence that Da Vinci had strabismus

Rufus46 / Wikimedia Commons David, a sculpture by Verrocchio for which he used Da Vinci as a modelRufus46 / Wikimedia Commons

British neuroscientist Christopher Tyler, creator of the three-dimensional optical illusions published in the popular book series Magic Eye, has been a pioneer in visual perception research since the 1970s. In recent years, Tyler has dedicated himself to the works of Leonardo da Vinci. His most recent discovery is that the Mona Lisa painter had strabismus—a condition in which the eyes do not properly align with each other when looking at an object—and may have known how to use it to his advantage. The conclusion was reached after analyzing six works. Four were created by Da Vinci himself: a self-portrait; Vitruvian Man; Salvator Mundi; and St. John the Baptist—all are believed to be based on the features of the artist himself. The other two pieces analyzed were the sculptures of David and Young Warrior by Andrea del Verrocchio, Da Vinci’s teacher, who often used him as a model. Tyler used circles and ellipses to measure the degree to which the pupils were misaligned in the eyes that featured in the works. One of Da Vinci’s eyes, he noted, was directed slightly outward (JAMA Ophthalmology, October 18). This characteristic may even have helped the artist to paint. Strabismus often causes a loss of stereopsis: the visual perception of depth and three-dimensional structure. But some people with the condition do not lose this perception entirely, and may even be able to “turn it on and off” voluntarily. This ability would enable a painter to observe something in 3D and then more naturally transpose it onto the two-dimensional plane of the canvas. The suggestion of three-dimensionality in a flat painting depends on particular signals, such as shading and perspective. Two techniques pioneered by Da Vinci, perhaps not surprisingly, involved shadows: chiaroscuro (the use of strong contrasts between light and dark) and sfumato (gradual transitions between colors). “Strabismus may have accentuated Da Vinci’s awareness of particular depth signals,” Tyler told Pesquisa FAPESP.