Q: What are the differences between free-form surfacing, digital surfacing, and direct surfacing?
A: These terms are interchangeable and refer to a lens surfacing method that utilizes design software to guide a CNC (Computer Numeric Controlled) single-point generator. Conventionally surfaced progressive addition lenses (PALs) have a front surface that is cast with the PAL design using a mold and surfaced on
|PFO offers premium brand free-form lenses called identity.|
the backside with a spherical or sphero-cylinder curvature utilizing a standard generator. More recently, surfacing laboratories have been using semi-finished spherical blanks and free-form surfacing the back surface to create the patient’s prescription as well as the PAL design simultaneously. Additionally, some lens designs also use a cast PAL design on the front and individualized “free-form” back curves to optimize the patient’s prescription. Free-form surfacing can also be used to produce standard spheres and cylinders to a much higher degree of accuracy (1/100th of a diopter) than conventional surfacing (which may achieve 1/10th of diopter accuracy). In fact, one lab, US Optical, processes 99% of its surfaced lenses using free-form equipment. Free-form surfacing will probably become the industry norm in a few years.
Q: If my patients are doing fine in conventionally surfaced PALs, why should I encourage them to spend more money on premium free-form designed and processed lenses?
A: Like many high-tech products from cell phones to HD TVs, the consumer’s experience is greatly enhanced with an upgraded product. Why not do that for vision too? After all, people need good vision to use all of those other products. Your patients will benefit from the enhanced vision, reduced optical errors (like marginal astigmatism, coma, etc.), and increased fields of view with free-form lenses. Companies like Shamir Insight, Inc., Seiko Optical Products of America, Inc., Pro Fit Optix, HOYA VISION CARE, North America, Carl Zeiss Vision Inc., and Essilor of America, Inc. have invested heavily in this technology which they wouldn’t do if there was no benefit to the consumer. Conventionally surfaced lenses are accurate to within 0.12D, but most premium lenses designed and surfaced with free-form technology are usually accurate to within 0.01D. Don’t you want to provide that accuracy for your patients?
Q: Are free-form lenses worth presenting to former PAL non-adapts?
A: These lenses offer a great opportunity to re-introduce non-adapts to PAL lenses. The earliest conventionally surfaced designs didn’t adequately compensate for power aberrations, distortion, and swim, so some patients totally abandoned PALs. Since most manufacturers warrantee their lenses for a period of time, this is the time to re-fit those non-adapts. My experience has been that most will like their new free-form PALs.
Another thing to consider is some labs also digitally surface lined bifocals like flat-tops and round segs. For those patients who just can’t use a PAL, this option gives them the optical precision of free-form surfacing in a visible segment format. You probably won’t use them often, but it’s nice to have them in your lens arsenal. They are available from labs like Luzerne Optical Laboratories, Ltd., and Expert Optics Inc. Check with others regarding availability.
A: Most lens designs are available in photochromic and polarized forms. There may be some limitations when it comes to PALs, but you can provide the same good vision indoors and outdoors with free-form lenses. Also any free-form single vision or PAL can be UV treated and tinted for sun use if it’s not already colored.
Q: Can free-form lenses be used for sporty wrap frames?
A: Using free-form designs, lens manufacturers can get around the old base curve problem by power compensating the lens to accommodate the frame wrap to provide an ideal visual experience for the wearer. Additionally, PAL wearers can take advantage of wrap designs with products like Shamir’s Autograph II Attitude™, Seiko Sportswear Transitions® SOLFX® sun lenses, and the EOS Wrap® series from KBco, The Polarized Lens Company. Pech Optical, Luzerne Optical, Rite-Style Optical Co., and US Optical are some of the labs that specialize in digital lenses for wrapped sunwear.
Q: When I receive a premium free-form lens from my lab, I can’t read it in my lensometer. How do I know if the Rx was done accurately?
|Some labs like Expert Optics are equipped to digitally surface lined bi-focals like flat-tops and round segs.|
A: These lenses are made with compensated powers that take into account a variety of factors like frame wrap, size, vertex distance, and pantoscopic tilt. Your lab will supply a printout of the compensated lens powers at distance and near along with the original Rx ordered. This is where trust comes in. Since you do not have the instrumentation to digitally verify the powers, you have to trust your lab. The compensated Rx will almost always not match the original Rx because of compensations. This is important to remember when sending the patient back to their prescriber because that doctor must be made aware that the lenses have compensated powers.
Q: Some labs offer ‘house brand’ free-form lenses. Are they okay to use?
A: A growing number of eyecare professionals (ECPs) believe they are. Labs like Expert Optics, Pech Optical, Luzerne Optical, Rite-Style Optical, and US Optical offer free-form “house brand” lenses too alongside the big name lens brands they sell. PFO offers premium brand identity and the value brand Acuity.
Q: Some labs require additional measurements for some free-form lenses. Why are they necessary and do I have to supply them?
A: Some premium free-form PALs ask you to supply additional measurements to the fitting height and monocular PD measurements you now take. If you
|Carl Zeiss Vision’s iTerminal helps take position-of-wear measurements.|
want to truly take advantage of the vision benefits these lenses offer, then you’ll want to take the time to do these extra measurements. These parameters are known as “position-of-wear” measurements and are used to compensate the final Rx because these parameters have an impact on the power of the lenses as they sit in front of the wearer’s eyes. In doing so, the lenses can be made more precisely and accurately for the way the patient will wear them. This kind of personalization has the potential for providing an improved vision outcome for the buyer.
Q: How do I take position-of-wear measurements?
A: Taking position-of-wear measurements is not difficult but it does take a little understanding and skill. One simple way to take them is by getting a fitting kit from one of the lens manufacturers. For example, Shamir has the Panorameter Kit to maximize its As-Worn Technology™. An informative guide comes along with the kit that shows how to perform each measurement. Another option is using a digital measuring system like the Smart Centration Diamond from ABS Inc., the iTerminal™ from Carl Zeiss Vision Inc., and the SmartEyePix from PFO. These instruments take electronic fitting measurements at the push of a button and deliver computer accurate results.
WHERE TO FIND IT
Essilor of America, Inc.
800-542-5668 • essilorusa.com
Expert Optics Inc.
800-892-0097 • expertoptics.net
Luzerne Optical Laboratories, Ltd.
800-233-9637 • luzerneoptical.com
888-274-6705 • mylensclub.com
Pech Optical Corp.
800-831-2352 • pechoptical.com
Pro Fit Optics (PFO)
866-996-7849 • profitoptix.com
Rite-Style Optical Co.
800-373-3200 • ritestyle.com
Seiko Optical Products of America, Inc.
800-235-5367 • seikoeyewear.com
Shamir Insight, Inc.
877-514-8330 • shamirlens.com
800-445-2773 • usoptical.com