FreeForm digital surfacing has enabled progressive lenses to be tailored front and back to suit the specific needs of every individual. In this issue we look at the evolution of this technology and the ‘families’ of Hoya progressive lenses.
Modern progressive lenses compensate for effective distance, pantoscopic angle, panaromic angle, higher-order aberrations (HOAs), unwanted astigmatism from progressive addition lenses (PALs), pupil size, head and eye movements. However, this hasn’t always been the case.
Earlier generations of progressive lenses were designed to bring about the experience of natural vision but they suffered technological limitations. The distance prescription could only be calculated along the horizontal and vertical meridians. In addition, conventional cutting techniques enabled only one prescription value to be optimised within one base curve range by spheric/toric back surfacing. All remaining prescription variations came close to the so called ‘base design’, but could not be optimised for individual wearers.
When people move their eyes to see, they not only look along vertical and horizontal lines, but also in oblique directions. Consequently, peripheral aberrations, especially in these areas, could not be solved properly… the quest to create the ‘ideal’ lens continued.
Because the lenses can be cut so precisely, each one can be optimised for every prescription
The emergence of FreeForm technology has created new possibilities in progressive lens design. Now the lens surface can be considered as a series of individual points, and, using FreeForm surfacing, each of these points can be cut ‘pixel perfect’ along multiple axes, instead of just two. Because the lenses can be cut so precisely, each one can be optimised for every prescription. Frame-, fitting-, and/or personal parameters can even be included in the lens calculation. As a result, a more customised or even personalised lens is within reach.
Hoya uses FreeForm surfacing to produce its two progressive lens ‘families’:
- the Summit TrueForm family of enhanced progressives, which uses TrueForm Technology
- the Hoyalux iD family of advanced premium progressives, which uses iD FreeForm Design Technology.
Both technologies are based on FreeForm principles, but have different features and benefits.
Hoyalux Summit CD and Summit Pro ‘TrueForm’ are the most recent FreeForm lenses to be released by Hoya. Summit TrueForm begins with a conventional Summit CD or Summit Pro blank. The wearer’s prescription is entered into HOYA’s Aberration Control Surface Design system, which produces a unique back surface by finely tuning the progressive design specifically for each individual prescription.
This process enables the design to be refined across all power combinations, removing the performance compromise inherent in conventional progressive lenses, and therefore ensuring visual accuracy for every wearer.
Typical conventional progressive lenses can only achieve target performance for one single spherical prescription per base curve. All other prescription combinations will contain some form of compromise in the design because the design is static and cast into the front surface. This is especially apparent in prescriptions that have a cylinder component as the cylinder can have a significant negative impact on the performance of a progressive lens.
HOYA’s process corrects the inefficiencies of the conventional front surface lens, allowing Summit TrueForm lenses to deliver consistent performance across all prescription combinations.
Benefits of Summit CD and PRO TrueForm include: –
1) Integrated Transmittance Control Technology
- Increases visual sharpness
- Balanced progression for each wearer
- Natural sight in all directions
- High tolerance offers complete visual freedom for each wearer
2) Addition by Addition Design
- Comfortable near vision for each wearer
3) Point by point FreeForm back surfacing
- Excellent Price/Quality Ratio
- Wearing the same design but now produced with a higher accuracy than before
- Easy entry to FreeForm produced lenses
4) Back Surface Aberration Correction
- Optimise visual performance over the entire lens surface
- Wider far vision than before
- Improved balance between far and near vision
5) Listing’s Law
- More comfortable and clear vision in all directions
The emergence of FreeForm technology has created revolutionary possibilities in progressive lens design… iD FreeForm Design Technology is characterised by a completely new surface structure in which the addition is divided into horizontal and vertical components (Figure 5). These are subsequently placed in the optimal position in relation to the eye, combining the unique qualities of both surfaces into a single, new progressive design.
With double sided aspherisation, the front and back surface function independently of each other, allowing one to correct the aberration of the other. In this way, the unique qualities of both surfaces are combined into one single, new progressive design.