Three-dimensional or stereoscopic vision is currently all the rage, from the latest movies and mobile phones to the most advanced devices used in clinical ophthalmology. It's worth noting that this isn't exactly "new," as interest in stereoscopic photography and binocular vision dates back a long time. Human stereoscopic vision is achieved by combining two slightly different perspective images from each eye, which the brain then merges and blends to create the sensation of depth or three-dimensionality.
How is 3D used in ophthalmology?
Medicine has explored the applications of stereoscopic photography and image analysis, particularly in the field of ophthalmology. For example, photographs of the optic nerve taken from different angles have been compared, providing a sense of depth between the optic disc and the neuroretinal rim, which is useful in diagnosing glaucoma. At our center, we work with state-of-the-art equipment that includes three-dimensional reconstructions of ocular structures, such as the latest-generation PENTACAM corneal topographer and the OCT-2000 3D optical coherence tomograph, which offers both static and moving three-dimensional images. These are especially useful in retinal pathologies. In specific cases, this type of imaging enhances diagnostic information, allowing our doctors to more accurately assess the depth, profusion, and location of lesions in the fundus, with the goal of always offering our patients the best technology.
But how did we get here?
During the Renaissance, Leonardo da Vinci studied the visual system from an anatomical perspective and extensively examined perspective. Interestingly, in 2012, a restoration study revealed that the copy of Leonardo da Vinci's Mona Lisa on display at the Prado Museum is the oldest in existence, leading to the discovery of what is believed to be the first three-dimensional portrait in history. German scientists Claus-Christian Carbon and Vera Hesslinger, from the University of Bamberg, analyzed both the original work in the Louvre and the copy exhibited in Madrid. The results of their research suggest that both works could have been painted in the same studio and simultaneously, likely by a student close to the master with direct access to his works.
In the image above, the work displayed at the Prado Museum is shown first on the left, followed by the original work displayed at the Louvre. The image below depicts a reconstruction of the positions the two artists supposedly took.
Driven by the hypothesis that Leonardo had the foresight to create both works from different perspectives, the German research team recalculated the positions the two painters supposedly held relative to the model while working on the portraits. Analysis of the paths between the reference points of both paintings revealed that the two versions do indeed differ slightly in perspective, finding a horizontal distance of 69 millimeters between them. This distance is close to the distance between the eyes (62-64 mm), giving each eye a slightly different perspective of space and creating the sensation of depth. In their study, Carbon and Hesslinger assert that if both canvases are placed together under cyan and red filters, the Mona Lisa appears to have a three-dimensional effect.
It is worth noting that Leonardo painted this picture in the early 1500s, approximately 300 years before stereopsis was officially defined by Charles Wheatstone in 1838.
Cristina Peña Betancor
Optician-Optometrist
NIVARIA CLINIC