Wrap Rx programs can help practices add this technical option to their lens portfolios. Image courtesy of KBCo The Polarized Lens Company

Wrap lenses work well if you know how and when to Rx them. This wrap primer offers Rx wrap technical and fitting tips

Wrap style lenses, so popular in plano, are now available in single-vision and PAL Rx formats. As materials and design options are ramping up, more lens and sunwear manufacturers are offering Rx wrap lens programs. In addition, some labs offer their own or manufacturer-based Rx wrap programs, and they have invested in wrap-capable processing systems. These companies are good sources for training materials, as well as premium-performing product.

Getting wrapped up in wraps now will help keep your practice on the cutting edge.

Today�s Trends

Current wrap lens power range is from around +4.00 to -6.00D. They are typically offered in eight-base or 8.25-base curves in a safety lens material like polycarbonate or proprietary, safety-certified materials. Lens blanks come in large sizes. For example, 83 diameter, with the built-in decentration necessary to provide excellent optics.

Asphericity is used to provide clear visual fields and to control lens profiles. These lenses require a sharper, steeper bevel than a conventional bevel�keep that in mind when fitting high-plus powers.

For high-minus patients, there will likely be a perceived size change of viewed objects. Frontside base curves combined with more vertex distance cause magnification, so objects may appear larger than patients� typical perception.

Wrap Rxs include base-in prism to compensate for induced prism from the wrapped axis and to correct distortion and blur. Formulas are used to determine the amount of Rx power based on patient eye and frame measurements, then the Rx power is compensated for the best visual acuity.

It�s important to consider not only how the Rx will interact with the frame, but also how the frame design and fit will impact the cosmetic appearance and functionality. Consider the following fitting points.

Frame adjustments: Always

pre-adjust the frame before taking measurements and be aware of how the frame interacts with the brow bone and cheekbones. Check pantoscopic tilt, since with most wrap styles the tilt/angle isn�t adjustable.

Measure PD, OC: All Rx wrap lenses require monocular pupillary distance and optical center measurements. With PALs, seg heights are a necessity.

Whenever possible, minimize the decentration relative to frame-to-patient PDs.

Curve consideration: The face- forming curvature of wrap frames is designed to fit closer to the face. When Rx lenses are added, this may cause lash crash, when eyelashes make contact with the lenses.

L

ens fit: Check with the manufacturer or lab to make sure that the lenses will cut out before ordering, and use a layout chart to confirm cut-out before patients leave the office.

Before stocking your shelves with Rx-able wraps, get frame construction details from each manufacturer to ensure their various wrap products are indeed Rx capable. This is especially true with rimless styles that often can�t be curved to accommodate wraps.

Final Product

Typically, wrap-savvy labs do the calculations. All eyecare professionals need to do is supply the measurements. As with digitally surfaced PAL designs, the fabricating lab should provide a printout for use when verifying Rx wrap lenses in the practice. This printout shows the compensated Rx used to create visually precise wrap lenses.

The compensated Rx that the lab produces based on the doctor�s Rx and optical measurements is what should be read in the lensometer, not the original Rx. The compensated Rx considers power changes when wearers look through the lens at an angle instead of perpendicularly. EB

Whether for sports or style, wrap eyewear designs continue to attract wearers. Today�s Rx programs meet the demand. Images courtesy of (top to bottom) Kaenon, Shamir, and

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