| Patients love rimless eyewear because it’s lightweight, comfortable and
disappears on their face. Just how popular is rimless? In 2006, about 15
percent of all eyewear sold in the United States was rimless; that’s about
one out of every seven pairs of glasses. However, the popularity of rimless has also created many technical challenges for those who fabricate
and dispense the final pair of glasses.
CONVENTIONAL RIMLESS
What comes to mind when we think of rimless? Usually, it’s drill holes,
compression mounts, screws and nuts, etc. By its very nature, rimless
includes additional time and special equipment to fabricate, assemble and
adjust the eyewear. Making rimless eyewear also requires special expertise
developed over time, typically after fitting a wide range of prescription
and frame types. As a result,
many opticians and offices
shy away from selling rimless,
and therefore, miss the benefits they provide the wearer
and the opportunities they
provide for their business.
I SYSTEM TECHNOLOGY
I System technology is a new
category of rimless: “drill-less
rimless.” Given the challenges of making rimless eye-wear, it’s not surprising that I
System technology was invented. It can be made in a few minutes without using any special equipment and it has improved vision benefits for the wearer. Because
I System doesn’t require drilling or notching, many of the problems associated with rimless eyewear can be avoided, while the advantages of rimless are still achieved.
As always, new technology means doing things a bit differently. Using
I System technology can significantly reduce the skill needed to become a
rimless expert. This minimizes the effects of staff rotation and can
improve patient satisfaction, dispenser efficiency and business growth.
The I System drill-less mounting system has several key benefits to the
patient:
a. Increased Visibility. Because there is no hardware inside the perimeter
of the lenses, nothing interferes with the patient’s peripheral vision.
b. Decreased waiting time. Because there is no drilling, there is no additional waiting time normally associated with making three-piece drill
mounts.
c. Cost benefit. There is no additional cost for drilling or notching the
lenses.
HOW IT WORKS
Instead of pins or screws, I System technology uses a steel
cable to secure the lenses to the
bridge and end-piece. The
cable (or wire) is hidden in a
groove in the circumference of
the lens and is virtually invisible
in the finished glasses. It passes
through the bridge to a connector hidden inside a hollow end-piece made of high-performance stainless steel. The cable is
tightened with a “Wire Tensioning Screw” and holds the
lenses securely in place.
Tensioning the cable maintains correct alignment of the lens and segment location and also creates the proper frame rigidity. The system also
allows easy lens removal and glazing. No stringing or re-stringing is
required, and adjusting is completed with common office hand tools. I
System technology is currently used in Pure Eyewear from Viva International, which has licensed the worldwide patent rights. (United States
Patent No.’s: 6,595,634; 7,104,645; 7,063,420 and 7,140,727. Other
patents pending worldwide.)
THE CABLE
The cable is made of multiple
filaments of stainless steel,
stranded to form a single
cable. Like the cable used in
suspension bridges, this construction provides significant
strength and is many times
stronger than the single nylon
filament used in semi-rimless systems. The twisted strand design provides efficient gripping action inside the lens groove. In addition, the
cable is plated with white platinum to make it virtually invisible when
the lens edges are polished.
THE ENDPIECE TENSIONING SYSTEM
The tension required to secure the lenses is accomplished using a clever
screw and barrel system in the frame end-piece. As the screw is tightened, the threaded barrel draws the cable tight around the lens. Because
the strand construction is continuous through the bridge, the tensioning
is controlled from two directions, above and below the lens. The cable
ends are secured in the barrel-shaped “wire connector.” Once tightened,
the lens will not move.
The distance the barrel travels inside the end-piece is longer than one
might expect, and that was done for the following reason. Edgers often
cut lenses with slight differences in size. Therefore, having a small
amount of play in the travel of the barrel can compensate for these slight
differences.
Also, some materials when grooved will leave small amounts of residue in
the groove and that will affect the final lens groove circumference. For cosmetics and a well-fitted job, the swarf must be cleaned from the lens groove.
Lastly, the screw is made of a stronger material than ordinary ophthalmic screws, since it must perform under a higher tensile load than
usual. Because of this, do not replace a Pure Eyewear or I System screw
with an ordinary screw. Screw kits are available from the frame manufacturer.
FABRICATING RIMLESS WITH I SYSTEM TECHNOLOGY
I System technology makes fabrication of rimless eyewear easy and fast.
Following the technical specifications for the key points listed below
ensures that finished glasses are made correctly.
1. Choose the right lens material
2. Understand minimum edge thickness needed
3. Know the dimensions for the groove
4. Manage groove placement
CHOICE OF LENS MATERIAL
Choice of lens material is important. Like all rimless, lens materials
should be more impact resistant, have little notch sensitivity and have
some flexural strength. Therefore, the best materials for rimless are poly-carbonate, Trivex (Trilogy by Younger and Phoenix by HOYA) and
high-index materials such as 1.67, 1.70 and 1.6.
Notch sensitivity is the tendency for a material to crack and/or flake
under tension when there is a small notch or micro-crack. Ordinary plastic lenses are highly notch sensitive and because of this CR-39 is not recommended for drilled rimless or I System frames.
THINNESS AND LIGHTNESS
Rimless is attractive to patients because it disappears. Whenever possible, choose higher-index materials for thinner and lighter lenses.
Use lens thinness charts to help show patients exactly what they can
expect in the final lens. Consider aspheric lenses in plus prescriptions to
reduce lens magnification and bulge. It typically provides the patient a
wider field of clear view. In addition, flatter front curves always make the
assembly and adjusting of rimless easier. High-front curves in high-plus
lenses adds complexity to any pair of eyewear, so use aspherics whenever possible.
COATINGS
Always choose anti-reflective lenses for rimless eyewear. Surface reflections detract from the overall beauty of the glasses, hide the patient’s eyes
and reduce their ability to see clearly, especially at night. Also, when higher-index lenses are used, surface reflections are increased. High index
requires AR for best results.
LENS EDGE THICKNESS
The width of the bridge and end-piece dictate the
minimum lens edge thickness at the mounting
point. The lens edge thickness must be a minimum of 2.5mm on current Pure Eyewear styles.
This ensures complete contact of the bridge and
end-piece edge against the lens edge. When this
is done, the frame front is firm and the end-pieces
do not flex forward or backward. Therefore,
ensure that the lab understands this requirement.
The correct lens edge thickness is necessary for
frame stability and proper adjusting.
In general, it benefits rimless lens stability to increase the minimum lens
edge thickness. For example, low power polycarbonate stock lenses are
thin, and in rimless, they are too flexible and have insufficient thickness
for grooving or drilling.
GROOVE WIDTH AND DEPTH
The cable requires that the groove is
0.5mm deep and 0.6mm wide. This
differs from a standard semi-rimless
groove, so it’s essential to make sure the
lab has these dimensions. Other
grooved frames also require different
depths and widths depending on frame
design. Edgers allow the depth and
width of the groove to be individually specified so it is easy for any finishing lab to accommodate this request.
Be sure the groove is cleanly cut and free of any “swarf” i.e., debris from
the grooving operation. Sometimes there will be some debris left in the
groove and this will affect lens size (circumference) and therefore fit. If the
frame components are loose after assembly, check the groove for swarf.
GROOVE PLACEMENT
In general position the groove in the center of the lens edge. When
ordering lenses or edging them in-office, specify that the groove should
be centered. This ensures that there is equal support for the front and
back edges of the end-piece on lens edge.
In a 2.5mm lens edge, this means that the minimum ledge on each side
of the groove is the result of the following: 2.5mm (lens edge) – 0.6mm
(groove width) / 2 (edges forward and back of the groove = 0.95mm.
Therefore, the minimum lens width needed for any ledge is 0.95mm or
about 1mm. Use this when considering high-minus lenses that are thicker than 2.5mm. In this case, the groove should be located about 1mm
behind the front edge. In this way, a thicker lens edge has a more properly located lens groove.
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Lastly, when considering groove position
and sizing, remember that high-base curves
change the actual lens size and circumference of the lens. Tracing the edge of sample
plano lenses of a new frame that are about a
four base, are a different circumference in
prescriptions that require an eight base, especially with decentration. For best results and
good looks, use aspheric lenses when possible. As a result, the flatter bases, i.e., flattened and aspheric lenses in
place of an eight base, will provide a flatter front and a better result.
In modern progressives, most designs are already flattened for better
cosmetics, so use the more modern designs. They look better and
patients see better with them too.
GLAZING: REMOVAL AND INSERTION OF LENSES
Use only your fingers or a stiff plastic ribbon like the one supplied with
the frame to glaze lenses. It’s the best method for placing the cable in
the groove. Hooks, pliers or other hand tools might kink the cable,
damage it and affect the final result. During insertion, place the cable
over the front of the lens and insert the lens into the top cable. With the
ribbon pull the bottom cable around the sharpest corner first and pull
the cable around the front surface into the groove at the roundest
shaped edge last. Then slide the ribbon to bottom center and slowly
slide it out. In this way, the least stress is placed on the cable and the
lens. It’s far simpler than a nylon frame where the nylon needs to be
stretched and often breaks. If the cable cannot be pulled around the
lens, the lens is probably slightly large. A quick touch-up in the edger
should correct this.
LENSES ONLY AND POF’S
Pure Eyewear and the I System create a unique opportunity for offices to
order lenses only and do the assembly in-office. This saves time and in
the case of a patient’s own frame (POF) job, the patient would not have
to lose the use of their glasses for a week or more.
Most offices send their rimless work to the lab for fabrication because the
office may not have finishing equipment, there is no one skilled enough in
finishing or because of the high cost of premium lens, the office prefers to
have the more difficult jobs done by experts. Pure Eyewear can be edged
and grooved at the lab and shipped to the office for assembly and dispensing. The reason is that assembly is easy and the patented tensioning system
allows for the slight sizing differences that might be received.
ORDERING LENSES.
Order lenses using the following guidelines for best results.
Materials. Choose: polycarbonate, Trivex or high index. Do not use CR-39 (standard plastic) and mid-index because they are too brittle and
flake too easily.
Lens Edge Thickness. Specify that the finished lenses must have a minimum edge thickness of 2.5mm. This ensures good frame stability.
Groove Dimensions. Specify the frame is Pure Eyewear and groove the
lenses 0.5mm in depth and 0.6mm in width.
Groove Placement. In general, ask the lab to center the groove for best
results.
Base Curve. Avoid very high curves and when possible use aspherics.
AR Coatings. Order AR lenses with polished edges.
TROUBLE SHOOTING 101
When working with new technology, it’s sometimes difficult to pinpoint
what went wrong when things don’t turnout as expected. The following
is meant to address a variety of possible “what ifs.”
The cable will not mount over the edge of the prescription lenses:
a) Completely remove the wire tensioning screw and end-piece from
the wire connector insert to provide the maximum cable slack for
mounting.
b) Check the Rx lens against the demo lens or pattern. The lens circumference should be as close as possible to the demo lens or pattern
circumference.
c) If the edger has slightly over cut the lens, retouch the lens in the
edger by -0.10 mm until the cable will mount with gentle pressure.
Remember to use your fingers and ribbon only.
The mounting is loose and flopping
a) Make sure the wire tensioning screw inside the end-piece is fully
tightened. Do not over tighten the screw or use excessive force, as this
can damage the mounting.
b) Check the lens circumference to insure the lens is not too small.
c) Check that the groove depth is at least 0.5 mm deep. If the groove is
too shallow the cable will be slightly above the edge of the lens and the
components will not contact the lens edge properly. Instead, the components will rock on the raised portion of the cable. If grooving by hand,
review that the groove is of a consistent depth. Shallow areas will make
the components loose.
d) Check for minimum 2.5mm lens edge thickness at the bridge and
end-piece.
e) If using polycarbonate, remove any swarf from inside the groove.
Debris will not allow the cable to recess fully into the groove.
The mounting is tight, but is unstable when the temples are opened
and closed
a) Ensure the lenses have a 2.5mm minimum edge thickness.
b) Check for center placement of the groove. If the frame components
hang off the edge of the lens, the mounting will feel loose when the temples are opened and closed. c) Examine the pin and safety bevels. Excessive beveling can reduce
edge thickness below the 2.5mm minimum required.
d) If lenses were polished by hand insure that the edge has not been
rolled or the lens shape distorted during polishing.
Lenses are cracking or chipping during inserting or final adjustment:
a) CR-39 (standard plastic) lenses are not recommended because of the
tendency to crack or flake. Acceptable lens materials are Trivex, polycarbonate and high index. b) Excessive bridge adjustments can
create excessive pressure on the lens
groove and cause damage. Remove the
lenses when making this adjustment.
CONCLUSION
Patients love rimless eyewear because
it’s lightweight, comfortable and disappears on their face. I System technology used in Pure Eyewear offers a
unique and proprietary frame system
that makes a new category of rimless
easier for the optician and ultimately
better for the patient. It’s rimless without drilling. Opticians quickly become
expert and patients receive eyewear
that makes a difference. ■
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