Vertical progressive component (image magnification in verticaldirection)

The horizontal and vertical progressive components.

While many attempts have been made in the past to eliminate the unstable feeling experienced by presbyopes, the results have been minimal. The time was right to take an entirely different approach in order to counteract these negative effects, combining existing know-how with the very latest software calculation programmes and production facilities. Before this could be done, the progressive design would require further analysis.

Vertical Progressive component and normal distortion, measured along the vertical planes.

Along the so-called ombilic line, a cross-section through the surface is circular and the radius of the circles in the vertical plane continuously decreases from radius far distance to radius near. Because addition power only increases in the vertical direction, an image enlargement will appear in the   vertical direction. Our visual system can easily adapt to this so called Normal Distortion.

Vertical progressive component (Position Front surface, far from the eye)

Horizontal progressive component and skew distortion, measured along the horizontal planes.

Measured along the horizontal planes, distortion/magnification negatively affects our visual performance because the far and near distance surfaces with tangential and sagittal radii curvature must be blended together in a continuously changing progression.
The results of the horizontal progressive components will lead to unacceptable deformation for presbyopes when the peripheral deformation is not correctly balanced.
This so-called skew distortion is uncomfortable for the wearer because it gives a swinging effect and insecure feeling when moving.

Horizontal progressive component (Position back surface)

Design principle.

Step 1: Individually defining the most effective position of the progressive components in relation to the eyes and calculating a unique front and back surface.

Step 2: Restructuring the separated design properties by a new virtual evaluation and calculation technique.

Step 3: Re-integration to complete the integrated total progressive design.

Expressing the right position of vertical progressive component.

What if the vertical progressive components were located on the back surface? More eyeball rotation will then be needed, because of the enlarged vertical visual field red lines/arrows) and enlarged interaction distance from far to near and vice versa. A longer vertical visual distance is needed to reach full addition value/compensation of the accommodation shortage. Positioning on the back surface will therefore have a negative influence on   the effectiveness in a vertical direction.

Conclusion: Vertical progressive components should be located on the front surface.

Result:  the shortest and most effective progression in the vertical direction, short and effective eyeball rotation, fastest compensation for accommodation shortage and fastest interaction between far and near.

Expressing the right position of horizontal progressive component and the influence of skew distortion.

The closer distortion is to the eye, the less image deformation influences the peripheral visual perception/performance. This was one of the reasons to position the horizontal progressive components on the back surface - it widens the clear undistorted visual field in a horizontal direction. As a result, the usable distortion-free corrective surface is enlarged, opening up new possibilities for a wider clear visual field at all distances, regardless of the prescription.

Vision - perception - experience.

Integrating both surfaces in the most efficient position is one thing. But the

goal when designing Hoyalux iD was to make a decisive step forward in reducing instability, providing multifocal wearers with an instantly recognisable feeling of security and natural vision.

Hoyalux iD took up the challenge by integrating the best of both worlds: Splitting Function (vertical progressive components/normal distortion) and Comfort (horizontal progressive components/skew distortion). Next, both the   vertical and horizontal progressive components were recalculated. This resulted   in an optimisation of both the functional part (effective interaction) and the comfort part (improved wide clear visual field). A short effective corridor length and the widest, distortion-free visual surface for all distances were created. Hoya calls this the Integrated Double Surface Progressive Lens.

Integrated design: Vertical progressive component at front surface and the horizontal progressive component in back surface.

The next challenge was to balance the new surface structure. Skew distortion would still influence the experience of wearing a progressive design if the newly structured front and back surfaces were unbalanced.

Evaluation techniques evaluating the quality of the progressive design.

Swaying and distortional complaints usually occur when wearing progressive designs, especially when moving. This effect can continue for years. The 'standard' progressive lens designs were the result of evaluation and calculation techniques that were available in the early days. While these techniques had also been dramatically improved over the years, the optimisation process had reached its natural limits.

Taking a totally different approach, based on 3D virtual evaluation and calculation techniques, we are now capable of calculating and quantifying the experience of progressive wearers by monitoring and evaluating the insecure feeling caused by peripheral deformation. Especially while moving, walking down steps and looking in oblique directions, this phenomenon can lead to non - adaptation and dissatisfaction. Before explaining the real revolution in Hoyalux iD's design technique, let us first clarify the improvement in design evaluation technology.

That is why Hoya has introduced:

Skew Deformation index mapping and 'Balanced View Control'.

Skew Deformation Index mapping is a new technology for evaluating progressive lenses. 'Balanced View Control' is also calculated by virtual computer simulation to show us how large a distortion results from looking through progressive lenses at various angles.
The following illustrations show Point Deformation and Skew Deformation (piano/addition 2.50D).
Point Deformation mapping includes a Normal Deformation and a Skew Deformation component. To achieve maximum information about deformation performance, it is best to consider these constituent parts separately. Skew deformation analysis is required to evaluate and quantify the distortion of vision suffered by wearers of progressive lenses, who are very sensitive to the resulting swinging effects.

Point Deformation Index mapping is calculated by virtual computer simulation to quantify the extent of deformation in each point of the visual field when wearing progressive lenses.

Point Deformation mapping includes:  

• Normal deformation component (vertical and horizontal component of Point deformation index)

• Horizontal direction( horizontal enlargement)

• vertical direction (vertical enlargement)

• Skew deformation component:(oblique component of Point deformation index)

Each coloured area refers to the level of deformation. The value of Point and Skew deformation index is divided in several groups, as 0.00 to 0.025, 00.25 to 0.050  Etc... (calculated power difference between horizontal (a) axes and vertical (b) axes of the spectacle magnification ellipse calculated by virtual calculation)

Skew Deformation Index mapping separately will detect more information about    Vision, Perception and Experience, especially evaluating the experience of unbalanced perceived images when the wearer of progressives shifts of eye orientations while moving.

New challenges.

The   new   concept   of   spectacle magnification and Point deformation indices (Point Deformation Index and Skew Deformation Index) makes it possible to examine the distortion of a spectacle lens, especially Hoyalux iD, precisely and quantitatively. This will undoubtedly help further improve optical design in the future.

Another, even more revolutionary, evaluation technique is the quantification of the experience of movement of an object or scene across the retina caused by a progressive design (the wearer perceives that the floor is pent or deformed, feels uneasy when descending stairs or feels like he is on a boat).

The way we see, interpret and experience images is being simulated and ntegrated in the virtual calculation program. This data are the basic input for stable natural vision with Hoyalux iD.

Hoya calls this evaluation principle 'Balanced View Control', and it functions   as follows. Computer simulation creates an original target image composed of a large number of small circles. The perception of this image travels along virtual lines of vision to traverse the progressive lens at a given point and then enter the ocular system. The following step is the calculation of a large number of retinal snapshots corresponding to the small target circles composing the target image.

After passing the progressive lens, what was circular becomes elliptic (ellipses are perceived on the retina of the model eye), indicating the deformation.
A spectacle magnification ellipse is formed for each point in the target image, describing how the image in the neighbourhood of that point is distorted when viewed through our test lens. The deformation caused by the lens is therefore defined by the spectacle magnification ellipses throughout the visual field.   It is necessary to quantify the extent of deformation for each point in the entire field.

Skew Deformation Index Calculation.

Skew deformation recalculation can help improve visual performance as well as reduce vision distortion and the swinging effect. A concept of "Skew Deformation Index calculation" has been   developed   to   evaluate   the unpleasant feeling caused by oblique deformation, where the degree of distortion caused by the lens is the basis for calculating the ratio of major axis "a" and minor axis "b" of the spectacle magnification ellipse. By recalculating the deformed peripheral progressive components, we are able to reduce skew deformation and achieve a much more comfortable feeling for the spectacle wearer.

Summary.

Integrated Design ensures that a progressive performance in terms of function   and   comfort   is   evenly distributed across the front and back surfaces. By keeping normal distortion on the front surface, vertical eye and head   movements   are   kept to a minimum.  Concentrating skew distortion on the back surface suits the eye better and results in extra wide scope across the entire far, intermediate and near vision area.

As  skew distortion is more uncomfortable for the wearer than normal distortion, it is crucial to normalise swaying and vision deformation effects. Integrating the new 'Balanced View Control' virtual evaluation technique, using computer simulation to analyse distortion due to looking through lenses at an angle, and integrating the 'Skew Deformation Index Calculation' technique all contribute to assurance and steadiness while wearing Hoyalux iD progressive designs.

Perfect interaction between far and near vision	No swinging effects while moving	Wide view at all distances

Hoyalux iD: the world's first Integrated Double Surface Progressive Lens with 'Balanced View Control':

•  Balanced and more comfortable peripheral distortion

•  Ergonomic dispersal of deformation over the entire surface

•  Wide intermediate corridor

•  More unlimited distortion-free areas

•  Perfect interaction between far and near vision

•  No swinging effects

To know more: Hoyalux opfficial site