L&T: RxPertise

May
2010

Wrap It Up

Ordering and dispensing wrap eyewear



Performance wrap eyewear is stylish, sophisticated and protective. But it takes the correct lens style, the safest lens material and the processing of frame and lens bevels to deliver perfection. This can be a lucrative niche in dispensing.

However, when it comes to wrap eyewear it is not a “cookie cutter” world. Balancing eyewear features with the technology of wrap eyewear is a challenge. The Pech Optical research and development arm of production utilizes advanced edging step milling to reduce edge thickness and fit prescriptions into wrap/sports styles, interchangeable lens eyewear and traditional non-Rxable frames.

Pech Optical refined nine different bevel styles with many variations to create various widths and depths of each bevel designed to meet each individual eyewear choice with an infinite number of Rx possibilities. The lab houses three manual and two automated five-axis, specialized edgers to fabricate this eyewear.

One of the challenges when working with wrap eyewear is the lack of information from frame vendors regarding the bevel used to manufacture a specific frame style. The two lists below show what information is traditionally given by lens or frame manufacturers. The Vision Council and Pech Optical has had open dialogue with several frame vendors to encourage more information, specifically the type of bevel being used.
 
Information from Lens Manufacturer
• Index of Refraction
• Abbe Value
• Segment Style
• Base Curve/Sag
• Coatings
• Thicknesses of Edges & Center
• Decentration

Information from Frame Manufacturer
• Eye Size
• Bridge Size (DBL)
• Temple Length
• Two-Dimension Pattern/Shape
• Dimension of A, B and ED

The newest technology in tracers broadens the information that can be obtained when working with wrap eyewear. Although standard tracers give critical information, Pech Optical purchased the Dimension tracer from National Optronics to gather more pertinent information when processing wrap eyewear.

Information from Standard Tracers
• Lens Shape
• Circumference
• Dimensions A, B and ED
• Bridge Size (DBL)

Information from National Optronics Dimension Tracer
• Frame Curve (face form)
• Bevel Curve
• Circumference
• Lens Shape
• Bridge Size (DBL)
• Dimenstions A, B and ED
• The ability to modify of A and B Dimensions

The following 10 questions and answers provide a guide for processing performance wrap eyewear.

Why bother with custom designed wrap eyewear?

Wrap eyewear provides the most comfort and best vision for performance eyewear. Coupling that with higher consumer satisfaction and repeat business will boost your bottom line.

Is it worth the effort to dispense wrap eyewear?

Yes. Many patients want Rx wrap eyewear styles they have seen in “plano only” versions.
Although some “wrap looking” eyewear can be dispensed “as is,” creating an Rx wrap often requires special skills on the part of the dispenser and their Rx lab. Since wrap eyewear comes in a variety of shapes and sizes, the dispenser and lab must determine which lens style, lens material and bevel style will provide the best fit between the frame and the lens. The lab must utilize CAD programming, custom designs and advanced, edging technology (Fig.1 and 2).


 
Is selling wrap eyewear profitable even if I can’t edge it myself?

Yes. Although the standard “V” bevel made by standard edgers is no longer viable for wrap Rxs, you can still make a profit on wrap eyewear because of the higher retail price it commands. The benefits of fashion and function (style of the frame, comfort as a wind shield, protection from UV exposure and glare, and safeguard from impact) affords a higher retail price tag. And the true ECP bottom line is that it benefits the patient with many choices.

Is it the dispenser’s responsibility to select the proper frame bevel?

No, it is not. The lab will determine the proper frame bevel. The lab will align the base curve of the lens with the base curve of the frame. “Base curve specific” frames require a special bevel configuration to make the lenses stay in the frame.
To achieve the best finished eyewear, follow these guidelines:
• Rx parameters: -5.00 to +4.00 w/ 3.00 cyl
• Materials used: Trivex, high-index or polycarbonate
• Lens availability: Cut-out, segment styles, lens colors
• Frames: Greatest impact resistance and comfort
• Wearer frame: Measurements and frame fit

If the Rx falls beyond these parameters, contact the lab for further evaluation.

How can the dispenser avoid compromising a patient’s vision when dispensing wrap eyewear versus dress eyewear?

Using lens optimization. Optimiziming a lens will maximize a patient’s vision while wearing a wrap lens. Optimizing creates a “sweet” optical zone that promotes wearer comfort.

How do I get a customer’s Rx optimized?

Ask your lab to optimize the Rx. The modification formulas used to optimize the Rx are fairly straightforward. Computer software from certain manufacturers streamlines the process. The calculations take into account the Rx power and/or wrap dimensions of the frame. The resulting optimization likely adds some base-in prism and small adjustments to power, cylinder and axis compared to the original Rx. These adjustments are ground into the lens during surfacing.
 
Why does the finished Rx received from the lab sometime differ from the Rx order?

Because the Rx has been adjusted for the customer’s position of wear. With the alteration of prism and power, the compensated Rx is often printed on the billing invoice below the ordered Rx to inform the prescribing doctor and/or dispenser of the change.

Can the new technology handle any sunglass frame?

It often does, but there are limitations and exceptions. Currently, open-ended hinges, snap fit metal frames, full shields and multiple base curve lens/frame combinations are not suitable for Rx wrap eyewear (Fig. 3). For best results of surfacing the thinnest lens and best optics, the lenses should be decentered within 5mm of the geometric frame center. This will validate “position of wear.”


Every frame has an optimum base curve, an optimum lens material and a specific power range for the best “as worn” Rx. A wrap lens often dictates a lens base curve change as well as consideration of the degree of wrap (faceform), the vertical pantoscopic tilt and the vertex distance. The wearer is looking through the lens on a different optical axis with the result of prism and blur, especially in higher powers. Only 10 percent of all eyeglasses worn would fall under the eight-base curve as the standard. That means there will be an infinite number that will have to be changed to fit and stay in a wrap frame.

Note: A dark mirrored lens in a rimless frame may prove a challenge when determining OC height and/or center pupil seg height. Have the wearer look to the side and dot where the canthus (angle formed by the juncture of the eyelids) with a white marker on the edge of the lens. Draw a line around the front of the lens from the white mark to the center of the lens.

How do I justify to the customer the additional charges that are on the Rx invoice?
Using a non-standard base curve and complex edging requires additional charges. Justifying these charges is easy using the protractor with frame demonstration.

Here is how to determine the need for advanced edging (Fig. 4):
1) Lay a protractor flat on a surface.
2) Place the frame on the straight edge with the temples toward the curved edge.
3) Center the frame.
4) Read the left and right numbers paralleling the edge of the lens to the degree measurements.
5) If the number is greater than 15° on the one side and 165° on the other, it will require additional handling.


Why does the wearer often come back in the first weeks after dispensing with a frame that is splayed out and unwearable?
A standard bevel was used rather than an inclined bevel. By applying an inclined bevel to the lens, the frame is able to properly relax around the edge of the lens (Fig. 5).

A standard bevel prevents the frame eyewear from properly forming around the bevels and results in ill fitting eyewear. The lens base curve determines the degree of inclination. The inclination ability of the five-axis edgers places the bevel on the same plane as the edged lens.

There are also frames that have a back bevel further forward than the front edge. These require a carve-out of the back lens bevel so the lens will stay seated in the frame. An easy method to check for this type is to remove the sample lens and place a PD stick against the lens bevel. Figure 6 shows the difference in two frames; the one below with the PD stick angled requires special edging.

Most business experts believe, on the whole, the world is going through a period of fast-paced innovations that will become increasingly intense in the coming decades. The reasons behind the push for innovation and creativity includes leveraging new technology, improving the consumer experience and increasing revenues. Cultures of innovation and knowledge do not happen overnight. They take time, patience and plenty of work, but they’re likely to pay large dividends in satisfied consumers and emerging healthy business growth.



Kathryn Gross-Edelman resides in Sioux City, Iowa where she is director of education for Pech Optical. She travels the nation as an educator and business consultant.

 

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