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Liberating Lenses
Direct surfacing technology and processing lets lenses be whatever they need to be. Here's what you need to know to understand the basics of this rapidly expanding lens category
By Karlen McLean, ABOC, NCLC

With industry experts predicting that direct surfacing lens production is the wave of the future, now is the time to get up-to-speed on this technology.

By understanding direct surfacing you will be ready to make informed decisions about what products you will offer and how to position these lenses.

Direct surfacing lenses will be the norm in three to five years. Image courtesy of Shamir Insight

TECHNOLOGY OVERVIEW

Direct surfacing is a process, not a lens. Simply, direct surfacing moves the semi-finished lens process into a lab environment.

■ The Equipment. The direct surfacing process utilizes special equipment. A free-form generator is cut-to-polish machine, allowing more precise prescriptions. This equipment has the capability to produce lenses with accuracy to +/- .05 D while traditional equipment is accurate to +/- 0.12 D.

■ The Software. When a free-form generator is combined with the appropriate optical software, each lens is digitally created. To manufacture complicated curves, this equipment is completely computer operated, driven by calculations called points files.  

Points files guide these generators in surfacing each lens design. Each points file is used only once, since a points file is programmed to a patient's Rx, and each lens has its own precise curves.

■ The Molds. Computer-driven generators include ceramic glass molds in which liquid monomer is poured to cast the lenses.

Many direct surfacing lenses start with a SFSV lens, needing fewer lens molds, while some begin with a front-surface design.

■ The Cuts. While traditional generators use diamond wheels to form lenses, free-form generators utilize a diamond tool that cuts surfaces with a single point.

In custom-made PALs, no two lenses are exactly the same. Single vision lenses can be highly accurate as well. Images courtesy of (from top): Essilor, Hoya, Carl Zeiss Vision

■ The Results. This process can produce virtually any lens, though the first direct surfacing lenses introduced to the optical marketplace were in the PAL category.

Custom-made progressive addition lenses create the exact Rx for each patient based on specific measurements and patient data.

No two lenses are the same. Highly accurate single vision lenses are also possible in wrap lens designs, high-powered Rxs, and in polycarbonate and high-index materials.

SPECIALTY LENSES

Currently, there are several specialty lenses that are direct surfacing processed for prescription accuracy and performance. Niche products like the TR O Segment and TR O Blended Segment offer additional options in no-line bifocal design beyond PALs.

More visually precise specialty lenses, like slab-offs and lenticular designs, are also possible. Lenticular wrap lenses are cut for minus-powered lenses and help blend away thickness in wrapped frame styles, sunwear, or sports eyewear.

ALL THE ANGLES

While each manufacturer has its own specific direct surfacing design criteria, there are some common basics that ensure the success of these designs, such as aspheric and/or atoric attributes. With the latest software and equipment capabilities, progressive curves can be placed on the front, back, or both sides of a lens.

■ Aspherics. Several companies promote aspheric design improvements in optics that reduce the oblique astigmatism that occurs when wearers look away from the lens' optical center. Direct surfacing aspheric design offers enhanced edge-to-edge visual clarity and the lens surface is flatter for improved cosmetics. Other manufacturers use a front spherical surface, placing the entire Rx on the back surface of the lens to eliminate front surface distortion.

■ Atoricity. Direct surfacing allows labs to generate and polish atoric surfaces, including single vision and PALs. Atoric curves are basically aspheric surfaces moved to the backside. This improves visual acuity by moving corrections closer to the eye and creates cosmetic benefits, such as thinning of high-minus lenses.

Lens Processing Lingo

As a fairly new technology, mastering the concepts behind the digital surfacing process may require adding to your optical vocabulary.

Here are a few terms to become familiar with in your quest for greater lens knowledge.

■ Aspheric/atoric: Curves on the frontside (aspheric) or backside (atoric) of a lens surface.

■ Cut-to-polish: When lenses go directly from surfacing to polishing, as in free-form processing.

■ Direct-to-surface/direct lens technology: Preferred general terms for free-form processing.

■ Free-form generation: A lens manufacturing process that creates sophisticated, precise lens surfaces.

■ Generating: The process of surfacing the prescription on the backside of the lens.

■ Software programs: Referred to as "points files" by several manufacturers and labs, these are used only once. As sophisticated programs, they guide free-form generators in surfacing each lens design.

Into the Future

Direct surfacing will continue to impact business into the future. While they won't eliminate traditionally surfaced lenses, experts agree direct surfacing and the resulting ultra-precise lenses will be the norm in the near future.

Direct surfacing and the resulting lens product are impacting the marketplace like evolving from glass to plastic material did in the past. This new production technique and lens products are the top priority at many companies.

Continuing changes in designs and implementation will cause lens companies to evolve. Design flexibility and the ability to consistently upgrade are important, and software should be easy to use. The process must be stable, and technical support is key. Verifying lenses properly is also key; direct surfacing-specific measurement equipment is being developed that is compatible with the software used to create the lenses.

While some manufacturers advocate internal production, other manufacturers are targeting independent laboratories and working with them to create direct surfacing product launches.

Experts agree that direct surfacing must add value at the consumer level. Branding will be important and will emphasize optical benefits and value. Costs will vary from inexpensive to expensive. Simply put, direct surfacing will change how the market in the U.S. is selling.