Hello, it looks like you are visiting from United States Language US - EN Go to United States (English) site

Understanding Free Form vs. Conventional

Ever since Benjamin Franklin fused two lenses together forming the first bifocal, man has continued to improve the design and accuracy of ophthalmic lenses. For hundreds of years, this refinement of optics eventually found a standard of design. It’s process, while tedious, requires:


  • Choosing a lens blank
  • Positioning and marking the blank up
  • Blocking the lens before any surfacing can be done


Download this PDF for a condensed version you can refer to as needed.



After surfacing the lens, the lab technician needs to choose the right fining and polishing tool to complete the lens production. This conventional technology of lens fabrication has the accuracy of 1/10 of a diopter and has been set as the standard of lens designs for a long time.


Over the past decade, however, a new form of lens surfacing has changed the way we see – so much so, that HOYA has decided to eliminate the conventional lens design completely and focus on progressive, free form lens design.



The present and future of vision

Free form or digital lens surfacing is an advanced, state-of-the-art surfacing technology. It utilizes highly complex computer algorithms to control a diamond tip lathe that carves the prescription into the back surface of the lens.


This allows for precise lens designs that can be tailored to all types of visual demands. There are no predetermined lens blocks or special tools for polishing. Free form lenses can be refined to 1/100 of a diopter or 10 times more than a standard conventional lens.



Conventional lens vs. free form

These refinements have optical advantages. Some comparisons made from a conventional lens design to a free form lens is like picking a suit off the rack compared to a finely-tailored suit – or perhaps viewing a standard TV screen versus viewing a high definition TV.


The true advantage is the advanced computer algorithms that are used to incorporate lens technologies into the lens design, maximizing binocularity and optimizing the progressive corridor.


Using advanced and complex computer algorithms to direct the diamond tip lathe, you can bring extreme precision to the lens design. A handful of factors are used in calculating each design, and there are two patented technologies that separate HOYA from the rest.



1) iD technology

iD technology takes into consideration the front and back surfaces of the lens. This technology calculates the vertical components of the reading corridor and places it on the front surface of the lens and the horizontal components on the back side. This allows the eyes to rotate quicker and more efficiently, downward through the corridor to get to full reading power – and it creates a wider corridor zone in the horizontal position.


2) Binocular Harmonization Technology (BHT)

BHT takes into consideration the prescription of each eye individually and designs the lenses as a pair, working together. Around 70% percent of the population has anisometropia or a difference in prescription between their two eyes.


This can be significant when the eyes rotate down the progressive corridors, as the reading powers will differ between the two lenses – especially the larger the anisometropia. The BHT computer algorithm takes this into consideration and adjusts the power distribution and corridor lengths to allow the eyes to work equally together, in binocularity, when viewing at near.



The perks of personalization

Some of HOYA’s premium lens designs are actually free form surfaces, both on the front and back sides of the lens for total personalization.


The beauty of free form technology is the ability to personalize. With the accuracy of 1/100 of a diopter and the ability for complex computer algorithms to incorporate advanced lens technologies, such as iD and BHT, superior optics for any task can be created. This allows you to tailor the lens design around your patients daily visual demands, making adaptation much easier.


Utilizing position of wear (POW) measurements brings another level to personalization. Think of the lenses in a frame sitting on the face as having a 3D position relative to the eye. There will be a certain wrap and tilt to the lens in the frame. Also, there is a distance from the back of the lens to the front of the eye. If we take into account these positions of wear, free form technology can enhance the wearing prescription even more – and also enhance the viewing prescription and the corridor size as compared to a conventional lens.



How Hoya does free form

Accurately capturing POW measurements can be easily accomplished by taking one photo with a tool like Spectangle Pro. The process is quick and efficient and brings a new experience for the patient that makes you look hi-tech.


HOYA is one of the most advanced lens manufacturers in the world, always advancing individual lens designs and lens treatments. You should always have access to the best possible products so you can solve your patient’s individual visual needs.


Again, the difference between conventional lenses and free form lens designs are so significant optically that I wasn’t surprised when HOYA decided to remove conventional lenses from their portfolio. It is my job, our job as ECPs, to ensure a future of superior optics for all of our patients’ optical needs, and the best way to ensure we do that is from free form-only designs.

HOYA has eliminated conventional designs and is bringing lens tech into the future. Ready to join us?

And if you found this content helpful, download this PDF for a condensed version you can refer to as needed.