A UK researcher has identified that evidence may suggest Leonardo da Vinci had intermittent exotropia, which may result in an ability to switch to monocular vision seen in some of his works of art. The researcher explained that da Vinci had an ability to draw or paint great artistic works, literally in the “eye”. The research showed that likely portraits and self-portraits (of da Vinci) may exhibit a consistent exotropic strabismus angle of −10.3°. Artists and sculptors may need to be seen in others’ evidence for strabismus, including Rembrandt, Dürer, Barbieri, Degas and Picasso.
The study, reported in the journal JAMA Ophthalmology (2019;137(1):82-86), showed that several works seem to point to an ocular misalignment of the gaze, an example of which is a bronze sculpture of David (1473-5, Bargello, Florence), by of the young da Vinci, or as observed in an oil painting of Salvator Mundi (Christ, the Saviour of the World, c. 1500), also attributed to da Vinci. Interestingly, the same painting in 2017 reached the record price of $450M at auction sold to a private collector. While the study only depicts 6 pieces of work of art, it is likely that similar other works could be uncovered within da Vinci’s catalogue. Assessment of the works in exotropia shows that the divergent eye alignment is “typically manifested as an outward shift in the locations of the pupils within the eyelid aperture”. The analysis of the effects of strabismus can be seeing at the direction of the pupils, irises or eyelid apertures, detected by the relative positions of the gaze.
The study of the strabismus showed that “the pupil position in the eye aperture from each figure to the angular rotation (assuming a typical eyeball radius of 125mm and an inter-pupillary distance of 60mm) quantifies the implied strabismus angles as −13.2° in David, −12.5° in Young Warrior, −9.1° in Young John the Baptist, 3.17° in Salvator Mundi, 5.9° in Vitruvian Man, and −8.3° in the elderly self-portrait (where divergence is indicated by a negative number).” The researcher, Dr. Christopher W. Tyler, of the Division of Optometry and Vision Sciences, City University of London, concluded that “the analyses of eye alignment are consistent with a diagnosis of intermittent exotropia, suggesting that Leonardo da Vinci had an exotropic tendency of approximately −10.3° when relaxed but could revert to orthotropia when attentive, as when inspecting his own visage for a self-portrait”.