Free-Form Facts

With free-form poised to take a solid 20 percent market share, and with your competition taking on free-form in a big (ahem, box) way, now's the time for your practice to take free-form by storm

Karlen McLean, ABOC, NCLC

Free-form designs are increasingly popular. Image courtesy of Shamir

Free-Form production and the lenses that result from it raise many questions from ECPs. How does free-form work? Is it really “all that?” To whom should I recommend and dispense it? And most of all, how can our practice feel confident with it? We've broken down free-form into five key categories: terminology processing, recommending, fitting, and follow-up. To get you started or refreshed here are the free-form facts, featuring a true-or-false question in each section (answers at the end of the story).

TERMINOLOGY

1. True or false: Free-form always means the resulting lenses are better than traditionally produced lenses.

These lenses and processes have many monikers, including wavefront, high definition, free-form, digitally processed direct-to-surface, and more. It boils down to this: The manufacturing process yields the product; free-form production results in a lens. The difference with free-form from traditional processing and product is that the lens is designed by advanced software that inputs specific data into free-form generators.

The resulting lens is only as good as the measurements, software computations, and generator/processing quality allows. So, the ECP (measurements), manufacturer (software design), and lab (processor) are each responsible for the success of the final lens product. Free-form manufacturing creates lenses unique to each company's proprietary designs and process.

Free-form has single vision and PAL options. Image courtesy of Hoya Lenses

There are three levels of free-form processing: basic, semi-personalized, and customized. Each can be explained by using a shirt as an analogy.

BASIC: Like a high-quality off-the-rack shirt. Lenses feature aspheric, atoric, or aspheric and atoric design, resulting in thinner, typically lighter, and slightly more defined vision than standard lenses.

SEMI-PERSONALIZED: Like an off-the-rack shirt with tailoring. These lenses feature everything a basic lens does and can be fabricated to fit the individual Rx, resulting in wider, more usable fields of vision.

CUSTOMIZED: Like a bespoke shirt. Lenses incorporate all the basic and semi-personalized features and benefits, plus can be fabricated to fit each individual Rx, complex measurements, frame shape and size, how the wearer uses their eyes, and even particular lifestyle usage.

PROCESSING

2. True or false: Free-form surfaces can be fabricated on both sides of a lens.

Front-side and backside free-form typically places Rx curves on the lens's back surface, while, depending on the manufacturer's design requirements, free-form design can be placed on one or both sides of a lens. Any design that's been researched and developed can be created.

The free-form process revolves around the appropriate software, programs, and equipment to produce premium PAL and single vision lenses. A free-form generator is a lathe-to-polish machine.

Free-form is descriptive of the computer-controlled process: A liquid monomer is cast in a mold, resulting in a single vision semi-finished lens blank which is “free-formed” under the guidance of sophisticated software. This process includes calculation, cutting, and polishing. Once the lens is made, the file is discarded.

The wonder of free-form is that set base curves don't rule the design; the design rules the base curves.

RECOMMENDING

3. True or false: Free-form lenses can yield the most natural spectacle lens vision for patients.

Free-form lenses offer crisp vision in every zone, with a wider field of view. Because the lenses are personalized, no two lenses are alike, so each offers finely-tuned vision. They are also thinner, so users will have crisper, sharper, more natural vision with more wearing comfort, and the lenses will look great.

Free-form lenses offer many levels of customization. Photos courtesy of: Carl Zeiss Vision (above), Seiko Optical Products (below)

Free-form production can create lenses with lower levels of unwanted astigmatism and power error. Aspheric and/or atoric design helps flatten and thin lenses and widen the field of view. Virtually all areas of the lens are usable with edge-to-edge visual clarity and maximized distance, intermediate, and near zones.

FITTING

4. True or false: All free-form created lenses require special, additional measurements.

Every PAL requires pupillary distance and fitting height measurements, and every free-form single vision lens order should include PD and optical center measurements. Some manufacturers' designs also require vertex distance, pantoscopic tilt, and face form measurements.

A few free-form designs are specialized for each individual patient's viewing habits, which are analyzed using specific measuring tools and systems. This allows lenses to be entirely customized for that wearer, especially in the lens's viewing zones and periphery. Your lab or lens manufacturer can offer training on using the measuring tool for the appropriate lens design.

FOLLOW-UP

5. True or false: I don't need to check the Rx on a finished pair of free-form lenses.

When the patient's new free-form created eyewear returns to the practice from the lab, there are often two Rx printouts enclosed: One is the as-prescribed Rx and the other is the compensated Rx. The as-prescribed Rx indicates the doctor's prescription, while the compensated Rx shows the Rx after free-form compensation. Check the Rx for accuracy in the lensometer by using the compensated Rx.

Troubleshooting free-form is typically the same as for standard PALs and single vision lenses. Doublecheck PDs and OCs for accuracy in case of blur or acclimation problems.

For PALs, lower the frame if there's distance blur, raise the frame if there's trouble finding the reading zone, and create more face form if there's peripheral blur. EB