Everywhere you look these days,
you will find consumers wearing sports wrap eyewear, from cyclists on the road
to golfers on the links to even businesspeople on the street. From their
unremarkable beginnings as a niche product in the 1980s, the wrap category has
grown dramatically. Adoption of wraps by high-profile professional athletes has
raised their profile. And specialty eyewear manufacturers are investing in
advanced design and manufacturing technology that has left most old-line
eyewear makers behind. Overall the sunwear category has grown to more than $2
billion of the $15 billion plus in annual optical sales.
It�s easy to understand the
popularity of wrap sunglasses. The curved, contoured eight-base polycarbonate
lenses in most wraps block UV, shield the wind, reduce glare and protect from
impact. They provide excellent optics tailored to all sorts of outdoor
conditions, whether cycling, golfing, hiking or fishing. They are designed to
be lightweight, comfortable and versatile.
Your customers are already buying
wrap eyewear�and maybe not from you, either. But they still need vision
correction when they are outdoors. Maybe some of your customers have already
begun to ask if you can provide Rx capability in their sports eyewear. This
course provides a key to prescription wrap sunwear.
WRAP EFFECTS AND OPTIMIZATION
The curvature and wrap that makes
the lens so functional in terms of lens coverage also requires care in setting
up the Rx. Compared to a standard �flat� lens in the same Rx, a wrap lens
changes the base curve and tilts the lens in the vertical plane. These changes
will affect the wearer�s vision, not usually for the better, unless the optics
is optimized for the effects of wrap. Fortunately, the optimization is well
TILT (WRAP) OPTIMIZATION
The primary optical effect of
wrapping a powered Rx lens is an offset in the prism and power of the lens as
perceived by the wearer. The fact that the wearer looks through a lens
differently when it is wrapped is key. To consider it another way, if you take
an ordinary �flat� lens of a certain Rx power and introduce wrap (faceform
tilt), the lens will still read the original Rx only when measured along the
original OC and visual axis of the lens. However, in the new wrap configuration
the wearer is now looking through the lens on a different optical axis
corresponding to the wrapped positioning.
The resulting prism and blur can
be objectionable, especially in higher powers. Even a plano lens introduces
prism when wrapped, causing discomfort for the wearer; this is why so many
ophthalmic manufacturers of better sunwear provide decentered (i.e. prism
corrected) lenses in their plano sports eyewear. In an Rx lens, the lens power
makes those effects even stronger.
Fortunately, the corrections
required to optimize the wrap are fairly straightforward and formulas can be
found in many ophthalmic optical texts. The calculation takes into account the
Rx power and the wrap dimensions of the frame, and the resulting optimization
usually adds some base-in prism at the eye point and small adjustments of
power, cylinder and
axis compared to the original �flat� Rx. These adjustments are ground into the
Rx during surfacing.
In the example opposite, to
create a -4.00 sphere for the wearer to satisfy a -4.00 sphere Rx, the lab
would need to supply a -3.75 -0.25 x 180 with 0.35� Base In.
How these calculations are
applied depends on who is doing it. In fact, many labs still fill a wrap Rx as
if it were a conventional flat frame, grinding the �dumb� Rx onto an eight-base
lens and mounting in the frame without regard to the wrap angle or optical
correction. The resulting optics is bound to disappoint your patient.
Labs that understand the need for
wrap optimization, however, have procedures for making the required
adjustments. For example, there are proprietary labs for processing wrap
prescriptions. These companies use proprietary formulas to calculate surfacing
optimization in Rx lenses or offer specialty wrap lens designs in SV and
progressive with additional atoric optimization of the front surface for
improved peripheral optics.
Specialty labs also may have
other tools and tricks for delivering wrap eyewear, such as surfacing processes
that are optimized for the steep back curves and large apertures of a wrap Rx
and edging and tracing solutions that can handle the sinuous frame grooves.
These labs can also assist with selecting which wrap frames are most suitable
Some manufacturers have built
their own dedicated labs to service their own products with factory-direct Rx
processing and OEM lens colors. Other brands have partnered with specific labs
to provide factory-approved optics and processes specifically tailored for
their wrap frames.
All this doesn�t mean that a wrap
Rx can�t be filled in your own office. The formulas and technology are out
there and a specialty wrap Rx service could be an attractive niche for your
practice. Talk to your lab to understand their capability and then decide for
yourself. (�Wrap Technologies� below includes additional discussion of wrap
ORDERING WRAP LENSES
If it is decided to outsource
wrap jobs to a lab, there are a few steps to follow. First, talk to your lab
about their capability and procedures, and make sure you understand the product
you are getting. Also ask if the lab has a list of frames they consider Rx
capable (and not capable) to assist in the frame selection process. Finally,
discuss their Rx range limitations and turnaround time capability.
When ready to place an order,
generally the process should be quite straightforward. Call or fax the order,
the job is started immediately, then supply the frame from inventory or have it
drop shipped from the manufacturer; the lab does the rest. Do not bother
working out the wrap corrections because the lab will do that and it could be
confusing if you try to second-guess their calculation by sending pre-corrected
MEASURING WRAPS � SURFACED VS.
When the job comes in and it is time to check the Rx accuracy, remember the
wrap-corrected Rx differs from the original Rx. If the lens is simply clamped
into your lens meter, the value will be the �corrected� power that was surfaced
into the lens. The lab that compensates the Rx will supply a checking ticket
that lists this corrected value so you know that your measurement matches their
Alternatively, try measuring the
eyewear in the �as-worn� position� that is, get your lens meter to look through
the lens along the same visual axis that the wearer will experience�which then
should report the exact power called for in the original Rx refraction. The
feasibility of �as-worn� measurements depends on the configuration of your lens
meter; manually position the frame over the read head and eyeball its position
to get the right alignment. It may help to open the temples and use them as a
guide; align the temples so they are parallel to the optical axis of the lens
meter and then read the Rx along the same optical axis.
BASE CURVE CONSIDERATIONS
As with any base curve change in
Rx eyewear, it is important to consider the effects of eight-base curves on
patients. The 8D base curve is selected for wrap coverage and to equal the
curve of the frame, not optics. Wearers may perceive a change in magnification
compared to their regular specs, especially in higher minus powers where their
regular lenses may be a two- or four-base. Increased vertex distance and front
base curves will increase magnification of the patient�s world. These changes
may also be more significant if the new sunwear does not have wrap-optimized
optics. Make sure to explain the differences to patient and inform them there
may be a short adaptation period required. Most patients love the fact they are
free from having to wear ordinary flat or uncorrected sunglasses outdoors.
Generally, wrap lenses are
recommended for a narrower Rx range than conventional frames, from perhaps +200
to -600 depending on the manufacturer. There are several good reasons for this.
For example, high minus Rxs can be very thick in the larger eye sizes typical
of wraps; wrap prism and magnification errors are more pronounced in stronger
Rxs; and higher minus Rxs can result in steep back curves that are difficult to
surface. Discuss Rx ranges with your lab and consider steering higher Rx
patients to other products (for example contact lenses combined with regular
For the most part vendors have
offered Rx wraps in single-vision lenses only, leaving out many wearers such as
the presbyopic golfer who wants to read her scorecard as well as her lie. In
expert hands, however, a variety of multifocal solutions can be delivered in
wrap frames. The same wrap corrections used with spherical single-vision lenses
can also be applied to spherical flat-top or round-seg lenses.
Progressives are tougher since
most PAL designs are optimized for specific Rx ranges, which in eight-base
designs means high-plus powers only; therefore the design may not perform as
well when ground to a more typical emmetropic or myopic correction. Alternative
solutions are softer design or spherical design progressives like AO b�Active,
Varilux Panamic or Younger Image where wrap optimized surfacing with a
wide-periphery PAL design can provide an effective wrap PAL solution. Talk to
your lab about their capability.
GETTING INTO THE DETAILS: FRAME
SELECTION AND FITTING ADJUSTABILITY
With many wraps, fitting is
either a �does� or �doesn�t� proposition. A large proportion of wrap sunglasses
are injection-molded plastic with limited adjustability. The shape of the
patient�s head and nose are often the primary factors in fit. However,
fit-friendly features do exist:
Some models feature adjustable
nosepads and/or temples.
Many wraps are engineered with
compliant parts that form to a wear-er�s face (for example, ribbed rubber
nosepads and flexible temples).
Certain brands offer two sizes
in popular styles to help find the best fit.
Most metal-frame wraps are made
with the same components as regular ophthalmic frames and thus are easily
Overall, the process of finding
the best fit is still going to be trial-and-error, and over time the models
that work well for customers� facial features will be learned.
SELECTING AND FITTING WRAP FRAMES
With limited adjustability,
fitting needs to be optimized on the first visit before the Rx is ordered. Have
a patient try on several styles and check the fit. To get the best sport
performance consider the following factors:
Nose: Requires comfort
and grip. The nose and temples must securely hold the frame in place during
active sports despite shocks and sweat. The wearer can�t take the time to push
the eyewear back in place while stretching for a point. Extreme conditions will
also expose the comfort limitations of a frame.
Temples: : Ensure secure
fit and comfort. Flexible, conforming temples may fit perfectly for one
customer yet create uncomfortable �hot spots� for another. Ask whether the
customer will be wearing the glasses with a hat or helmet as this will affect
Lash crash: Many wraps
fit very close to the wearer�s face and their eyelashes could contact the wrap
lens. Keep in mind the Rx solution that will be employed; most lens-in-frame
styles place the front surface flush with the frame front, bringing the back
surface closer to the lashes. Clip-on styles add an additional lens element
between the sun lens and the eye, further reducing the available space. In many
cases the shape of the person�s nose will determine whether a particular frame
will fit or not. Keep an Rx lens or an Rx clip on hand to try on with the
Vertex distance: : In
stronger prescriptions, a large change in vertex distance compared to the
patient�s optical frame could affect the power and magnification experienced in
the new wrap pair. Measuring vertex is difficult with wraps, but try to select
a frame that keeps the lens about the same distance as the optical frame.
Coverage: Since the
patient expects good sun and wind protection from a wrap, watch for gaps at the
cheekbones, eyebrows and temples. Most wraps are not panto adjustable, they
either work or they don�t. In shield or rimless models, manufacturers often
offer multiple lens shapes of different depths that may help with coverage.
Remember that deeper B sizes also curve in toward the face more due to the
eight-base curvature, giving the effect of greater panto. Have the patient wear
the frame outdoors to check out sun protection.
Field of View: For Rx
wraps, particularly clip-on models, consider the wearer�s peripheral vision
needs in the intended application. Place the frame on the wearer and have them
strike a sport-specific pose. Does the frame provide sufficient view through
the periphery of the Rx lens or clip to see the pitch or putt?
Weight: : Consider the
weight of the eyewear with the Rx and/or clip, which in higher powers can
double the weight of a lightweight plastic frame. The movement and bouncing in
sports puts a premium on fit. Don�t be afraid to have the patient jump up and
down to see if the frame stays put.
Style: Considering the
radical look of many sport sunglasses, some wearers could be self-conscious
about the �attitude� that comes with the performance. Additionally, wearing a
pair of dark glasses in the store under artificial lighting, without
correction, can make it hard for patients to judge the look. Consider using a
virtual mirror or a digital camera to capture an image of the wearer.
For many wrap sunwear styles, the
only Rx solution available for many years has been an Rx clip. A clip mounts
behind the frame front and accepts clear lens inserts in a more or less
traditional plastic or wire rim. The benefits of this system are:
Availability: Makes Rx
available in a wider range of frame styles.
Flexibility: Many styles
give the wearer the option to insert different colored interchangeable plano
lenses for different light situations, which is a popular option in the plano
sun market. Also, contact lens wearers can remove the Rx clip altogether when
they choose to wear contacts with their sunwear.
Simplicity: Since clips
are built more like traditional frames, they are straightforward to Rx without
specialized equipment, often even in-office. Also, clip sales mean extra
revenue from the sale of the clip itself since it is usually offered separately
from the frame.
However, clips have a few
drawbacks to consider:
View: Most clips have
smaller apertures that restrict the wide field of view wearers expect from wrap
sunwear. Some wearers may compare this to looking through a keyhole.
Fit: Clips add weight and
volume behind the lens, affecting fit and lash-crash. Some types require a
stacked nose-bridge that pushes the frame away from the face, compromising the
Optics: Clips introduce
multiple surfaces that reflect light and attract fingerprints. Additionally,
clips may not offer advanced wrap-optimized lenses that many suppliers offer in
full-frame wrap eyewear, so prism and blur may be an issue. In general, though,
clips tend to have less wrap than the parent frame and therefore present fewer
FULL-RIM AND THREE-PIECE WRAPS
When it comes time to Rx these
frames, it is generally easy going since three-piece and conventional metal
frames share the same materials and mounting features as conventional optical
frames. Many suppliers are also starting to design injection-molded plastic
wraps with Rx capability. Still, there are a few practical issues which must be
For a full aperture, true wrap Rx
solution, many manufacturers offer eight-base wraps in full-rim and three-piece
styles. These offer advantages to the wearer such as:
Full field of view: The
lens fills the entire aperture of the frame providing the widest possible view.
Seamless integration: Instead
of clipping to the back, the Rx lens takes the place of the plano lens for an
integrated, �factory original� appearance.
Reduced volume: Eliminating
the clip eliminates much of the concern over weight and lash crash.
Wrap optimization: Even
though the detailing of these frames may look conventional, the wrap
configuration and eight-base lenses make these frames the prime candidate for
wrap Rx optimization. Filling these frames with a �dumb� Rx could result in
compromised vision for your patients. Also remember to send the actual frame in
with the order so the lab can measure the correct wrap parameters before
Cutout: Since wraps
generally have larger eye sizes than most ophthalmic frames, lens cutout could
be a concern with certain lens products in smaller blank sizes. Discuss with
your lab eight-base SF/SV or progressive lens availability to ensure good
cut-out. Specialty wrap lenses like SOLA�s Spazio feature larger diameters and
decentered optics to provide adequate cutout in nearly all applications.
Edging and mounting: While
the wire or channel on a full-rim frame may look conventional, the edging
challenge is not. Tracers designed for flat frames may have trouble following
the steeply curving bevels of a wrap frame. In edging, the sharp corners and
curving can cause trouble for the surface probes and large diamond wheels of a
conventional wet edger, leading to poor bevel shape and placement. Equipment
which works well with wraps, such as the National Optronics� 4T tracer and 6E
edger uses a 3D trace and router cutting blades to produce custom bevels.
Plastic frame compatibility:
Inspect injection-molded plastic wraps carefully for Rx edging compatibility.
Unless they are designed to accommodate an Rx bevel, the grooves are usually
shaped to grip square-edged plano lenses and may have a wide rear flange that
prevents Rx mounting. Additionally, thick plastic structures at the nose or
hinge area could interfere with thick Rx lenses. Your lab may be able to help
you select frames that are Rx capable.
frames require additional attention. First, make sure the studs or screws are
long enough for thick Rx lenses. Some screws are countersunk into the lens and
will not require cutting. Second, make sure the base curve of the Rx lens
matches the base curve of the original plano; sometimes three-piece wraps use
tilted six-base lenses instead of true eight-base wraps. Using the wrong Rx
base will change the fit, wrap and apparent temple length. Finally, drill holes
at a perpendicular angle to the front surface, otherwise the frame pieces will
not mount flush and the wrap and fit will be compromised. Fortunately, newer
drillers are starting to pay more attention to this requirement.
Beyond clips and lens-in-frame
models, a few manufacturers have developed unique Rx solutions that fall into
neither category. One example uses a specially designed Rx element implanted
into a plano shield, giving full coverage with a minimal lens profile. On the
horizon, companies are working on advanced machine technologies that in the
future could offer full-frame Rx lenses even in the more challenging rimless
styles, opening up frame selection and eliminating the need for clips. These
advanced technologies require working with a specialty lab.
PULLING IT ALL TOGETHER
To put this knowledge into
practice, use the optics, selection and fitting of frames, and ordering and QC
of wraps discussed here. Wrap eyewear can be a successful and popular specialty
for your practice and a great way to satisfy patients with optically advanced,
functional eyewear and a terrific second pair opportunity. As you develop your
understanding of how to match patients to the right eyewear and deliver a great
Rx, they will keep coming back for more.