August 1, 2023
Artificial Intelligence (AI) is in its infancy, and yet the technology has already demonstrated its value in the design of progressive addition lenses (PALs). EssilorLuxottica has employed this new tool in the design of its Varilux XR series of lenses. Additionally, physiological optics (a course I struggled with in optometry school) has also been implemented in lens calculation models. The value of physiological optics and psychology combined in determining the optimal PAL lens design becomes readily apparent when studying EssilorLuxottica’s rationale for modern lens structure and design.
We are aware of the increased demand on our visual system, especially our near vision, in today’s modern world, particularly attributed to the increased use of mobile digital devices. We are constantly switching our gaze back and forth between various different tasks and from far to near and back. It has been estimated that we move our eyes from target to target as many as 100,0001 times each day. Nearly all age groups use digital devices in some part of their daily routine. As our dynamic vision needs keep changing, we need new lens solutions to optimize our visual needs.
Today’s presbyopes demand a progressive lens that will allow the navigation of the eyes through the lenses while moving from one object to another. Furthermore, our visual system operates in a 3D, not a 2D, environment. Optical modeling must take this phenomenon into account if the most precise lens system is to be designed. EssilorLuxottica has created a new approach to progressive lens design that manifests itself in the next generation of Varilux lens series.
Ocular Navigation
The concept of ocular navigation has been embraced by EssilorLuxottica. This means that we need to place our fovea as precisely and quickly as possible on the relevant targets that we are interested in viewing. This is even more important when we are on the move, known as in-motion multitasking. This has led to the new Varilux XR-motion technology. This technology encompasses the natural strategy of ocular navigation and thus minimizes the visual challenges related to the use of progressive lenses in complex situations. EssilorLuxottica (as well as other lens manufacturers) realizes that the quality of the binocular image and balance between images is important for clear, comfortable viewing. This binocular optimization is necessary to provide the best binocular visual acuity while minimizing the difference in image quality between the right and left eye. EssilorLuxottica refers to this process as XR-Motion, which considers a point of reference in a 3D environment. The result is a reduction of power and astigmatism disparities in the central vision for a wide range of gaze directions. Because of this, the Varilux XR series lenses provide optimal binocular visual acuity and binocular balance for a wide range of gaze directions and ensure the best ocular navigation in challenging situations of multitasking in motion.2
Eye Movements
When we depend on our highest level of acuity, we are limited to the central 2° of our central visual field. Because of this, we have to shift our gaze at regular intervals three or four times every second to bring objects of interest into the fovea to make them available to our attentional system to be processed.3 This succession of saccades and fixations builds the representation of the surrounding visual environment.4 When viewing objects at a given distance, the saccadic eye movements require both eyes to move conjugately with the same amplitude. When shifting gaze between targets located at different distances along the midline, we employ symmetric eye movements in which the two eyes rotate with equal amplitude in opposite directions.5
To shift our gaze between targets located at different distances, not along the midline, we generate disjunctive saccades, produced by the two eyes rotating in the same direction but with different amplitudes.6
Ocular navigation is key to shifting attention between objects and tasks. In our daily dynamic environment, the scene elements are distributed over a 3D space at various distances in motion relative to each other and to the observer. The crucial role of good stereo acuity is especially sensitive in multi-object tracking tasks. Plourde and colleagues (2017)7 showed that performances were significantly better with good stereo-vision when subjects were instructed to track several objects moving continuously relative to each other.
Behavioral Artificial Intelligence
The EssilorLuxottica digital twin is an artificial intelligence system providing a realistic indication of spectacle-wearer perception through lenses by simulating the wearer’s experience with their lenses in a 3D environment. This AI tool allows perceptual, physiological, and biomechanics models that relate measurements to performance indicators:
- accommodation efforts as a function of accommodation value
- visual acuity as a function of lens aberrations and visual characteristics of the virtual wearer
- head and gaze efforts as a function of head and gaze directions
Based on the above information it can be concluded that EssilorLuxottica and its XR-motion technology, which has been developed for its new Varilux XR series, has utilized the newest AI tools along with sophisticated physiological and psychological optics to bring a new level of visual optimization to the market. ECPs and their patients can enjoy a new level of vision comfort and accuracy with these lenses.
References
1, 2 Essilor White Paper on XR Series lenses, 2023
3, 5 Findlay, J. M. Gilchrist, I. D. Active Vision: The Psychology of looking and seeing. Oxford University Press. Online Ed. 2003.
4 Gegenfurtner KR. The Interaction Between Vision and Eye Movements. Perception. 2016, 45(12): 1333-1357.
6 Quinet, J, Schultz, K, May, PJ, Gamlin, {D. Neural Control of Rapid Binocular Eye Movements: Saccade-Vergence Burst Neurons. PNAS. 2020; 117(46):29123-132.
7 Marjolaine Plourde, Marie-Eve Corbeil , Jocelyn Faubert. Effect of age and stereopsis on a multiple-object tracking task. PLOS. Dec., 15, 2017.
