Photograph by Iris Johnson; Frame: Scott Harris Underground 06 from Europa

Across the country, a small group of progressive optical practices are hearing testimonials of great satisfaction from clients who have purchased eyewear with free-form single vision (FFSV) lens technology. But even as stories of overwhelming success filter down to both professional meetings and social media sites, many eyecare professionals continue to cast a wary eye both to the cost and promised benefits of digitally-enhanced optics. Ask a typical eyecare professional why they’re not fitting more FFSV, and the responses range from “too expensive” to “They won’t see a difference,” to “Who can really notice one-hundredth diopter accuracy?” Overall, the tenor of these responses can be summed up as “If it ain’t broke, don’t fix it.” But this attitude suggests that many ECPs continue to misunderstand what the full package of optical benefits this technology can deliver.

From expanding the sweet spot of crystal-clear vision, to optimizing fit using custom matching of lens base curve to frame or groove curve without optical degradation, to making prescription eyewear appear as beautiful and appealing as plano, free-form SV technology allows eyecare professionals to deliver the ultimate trifecta in eyewear: superior vision + optimal fit + “authentic” cosmetics. All it takes is embracing how FFSV technology can finally set you free from being addicted to using stock lenses.

So why hasn’t the superiority of free-form (FF) technology overtaken the single vision eyewear market? Maybe it’s because interest in FFSV lenses has been pushed to taking a back seat behind applying digital lens technology to progressive and wrap eyewear, which is where most ECPs feel the “fire” is. Here, optimizing clarity, comfort and utility tends to consume most of our time and attention. At the same time, vendors have been placing their marketing and instructional seminar dollars toward addressing problems and misunderstandings with progressive and wrap eyewear. Further, the conventional wisdom is that we’re not hearing many complaints from SV wearers centered on lens design. Rather, ECPs look at refractive index or Abbe value—aka color error—as the primary culprits causing visual dissatisfaction in SV lenses.

Yet another reason to avoid FFSV lenses may be far simpler: complacency. While striving to keep material costs down and remain profitable, ECPs aren’t sensing a compelling reason to offer more expensive lens solutions, using stock lenses. Already tired from fighting wars about the benefits of AR and photochromics, most ECPs tend to resist putting another upgrade choice on their client’s menu, especially if it’s not covered whole or in part by vision insurance. The problem here—of being satisfied with the same old status quo—is that any business’ long term success is undermined by being satisfied with adequate as opposed to excellent. As the exponential growth of online eyewear shows, delivering adequate eyewear, or “good enough eyewear,” is rapidly moving down the path toward commoditization, where prices and profits are in decline.

During the last 300 years, the main task of lens designers has been to expand the areas of super sharp vision available to the wearer. Both best form and corrected curve lenses are among the best in this respect, and have been considered to be the gold standards for optimal acuity. But these lenses will only deliver their promise of superior sharpness when fitted in accordance with the following rules:
  • Vertex distance of 13.5 mm—the default of most lens designs
  • Pantoscopic tilt of zero for an OC height on center, adjusted 0.5 mm down for every degree of tilt (Martin’s Rule of Tilt)
  • Zero frame wrap angle, also known as panoramic angle, i.e., “flat” eyewear
During the middle of the 20th century, considerations of frame fashion started to interfere with best form fitting. Finding that their clients objected to the weight and thickness of lenses optimized for proper base curve, optimal alignment for PD and pantoscopic tilt, opticians and their labs began to compromise and move away from strict adherence to best form. Their clients, meanwhile, appeared more than willing to “get used to” compromised vision for the sake of style and fashion.

For most of the 1990s, the typical eyewear dispensed featured low Abbe lens materials, flatter base curves and improper optical center placement. But the potential effect this acuity-degrading recipe had on client vision was offset by the fashion trend toward tiny eye sizes. Smaller, narrower frames ended up trimming the most offending areas of poor correction. The result was a paradox: At the same time that we dispensed some of the worst optics in 100 years, the complaints we heard from clients were negligible because they were satisfied with their eyewear’s thickness, weight, appearance and vision.

Around 2005, digitally-optimized lenses entered the marketplace. With an initial cost nearly double or even triple that of off-the-shelf stock lenses, eyecare practitioners couldn’t be faulted for not embracing digitally-enhanced technology. However, today’s prices for FFSV lenses have fallen and are quite comparable to other premium finished lens products. There is no better time to begin “wowing” your customers with the total visual excellence of free-form single vision lenses.
Prison or Promise?

I wish I had a nickel for every time I’ve received an Rx without an acuity notation or vertex distance, but with the remark “match base curve.” Whether it’s back to your office or the doctor’s, when patients find their glasses “feel funny,” they’re apt to return for assistance. Although taking the time to tease out if base curve is the offending element is part of our job, it’s also time that could have been more productively spent elsewhere. As people display varying sensitivity to changes in position of wear, Rx, eye position, lens curve and material, it’s no wonder many physicians use “match base curve” as a convenient catchall, hoping to reduce symptoms of discomfort. With a new Rx in front of you, the question of deciding to follow a doctor’s recommendation of matching a base curve poses a dilemma. Certainly base curve changes can significantly impact peripheral vision and comfort. But as much as we’ve learned that tilting or angling a pair of uncomfortable glasses can reduce patient discomfort, it’s clear that “uncomfortable” is really a catchall for the combined and interdependent effects of all the parameters in eyewear specification. This is the prison that matching base curve has represented… until now.

With FF technology, it is possible for opticians to specify their choice of base curve, which will then be used as the new basis for real-time lens optimization. By using the higher surface precision and zonal optimization inherent in the free-form design process, dispensers can now select their choice of base curve, dependent on availability and material substrate. Through this process, no longer will a client select a frame style for its fashionable appearance, and then discover that the traditional curve of their prescription has deformed it from its original factory alignment and appearance. And it doesn’t matter if the frame is metal, plastic or grooved construction. Thicker, flat metal profile frames are especially well-suited to this type of custom frame/base curve matching. Even with free-form technology, changing base curves can still prove to be risky. Using the following guidelines should be helpful:

  • Be familiar with traditional best form base curve recommendations. With the Rx in hand, dispensers should know what the recommended traditional base curve is. Be aware that this value has been correlated to the index of refraction for basic plastic or glass lenses, between n = 1.50 to 1.523. There is an inverse relationship here—selecting a higher index material necessitates the use of flatter curves to remain in compliance with the best form correction.
  • Determine the frame's bevel curve. Although clocking a lens template is often sufficient, the best precision is obtained by using your frame tracer to isolate this value.
  • Don’t forget wrap angle. Use a protractor to determine frame panoramic angle. Together with the original Rx, lens index, best form base curve and frame bevel curve, arrive at a “seat-of-the-pants” value which balances the interaction of all these factors.

With a modest amount of experience, you will be surprised how easy it is to create finished eyewear which maintains the authentic factory frame appearance and fitting comfort. Be sure to point out to your customers the superior acuity and cosmetics that FF technology allows in expert hands. Wearers will still need to be cautioned to allow a little time to get used to their new vision and perspective. The difference is this time you’re not at all brushing them off. They simply need time for their visual system to unlearn all the compensations they’ve had to make with their old, inferior pair of eyewear. It’s not uncommon to hear patients comment that a day or two after they received their new FFSV eyewear, their vision just “clicked” and has been terrific. It’s a win-win: Everyone agrees that the additional price of FFSV lenses is worth it.



For almost a century, the benefits of best form lenses were only possible with eyewear fitted with strict adherence to fixed position of wear values. Today, few patients will accept that their fitting, facial characteristics or aesthetic preferences have to be ignored to realize the best vision. Through individual specification of vertex distance, pantoscopic tilt, frame wrap and lens curve, FFSV lenses provide eyecare professionals the tools and freedom they need to create the ultimate visually and cosmetically perfect eyewear.
While there are degrees of optimization possible in free-form technology, the best consists of four parts:
  1. Measurement and input of all tailored fitting and position of wear (POW) values, including base curve.
  2. An uploaded tracing of the actual lens shape and size.
  3. Real-time design optimization of the global lens surface.
  4. Free-form precision manufacture, guided by computer numeric control.
Although minor strength Rxs may show little benefit from FF technology, most moderate strength or astigmatic prescriptions and unusual fitting situations—such as a high pupil height combined with little pantoscopic angle—will deliver acuity demonstrably better than using stock lenses. The visual improvement is often so pronounced that FFSV lenses can take their rightful place alongside prescription changes as methods to sharpen vision. No longer does “no change” automatically mean no new glasses.

The advent of FFSV technology is ushering in a unique and rare opportunity for eyecare professionals. For the first time in almost a century, your patients can begin enjoying the new gold standard in eyewear excellence: the ultimate trifecta of acuity, fit and fashion.

Today’s paradigm for ensuring business success doesn’t just lie in giving your customers what they want. Rather—and taking a page from Apple’s playbook—it’s in giving people what they truly want and need, but just don’t know it. If Steve Jobs ran an optical business, he’d be tweaking every pair of SV glasses he sold with free-form technology. Jobs would innately understand that customers only want eyewear that embodies optimal vision, fit and fashion. And he would strive to be the first in his area to give this terrific technology to his customers. Like the legions of Apple product owners have demonstrated, people are willing to pay for excellence. They not only become your best customers, they are willing to enthusiastically spread the word of how insanely great your eyecare practice is. If Jobs could see the benefits in evangelizing all of free-form’s manifold benefits to every one of his customers, it’s obvious that so should you. ■

Barry Santini is a New York State licensed optician based in Seaford, N.Y.