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In the current edition of the
Progressive Lens Identifier there are over 300 progressives illustrated
covering design and materials. That means that the ECP prescribing and
recommending progressives, has numerous choices from which to pick. Therefore,
the requirement is to limit the choices to a workable few.
The question is what criteria the
practitioner should use to select a particular progressive for a particular
patient. Which progressive will become the standard by which to judge others
and whether to include them in the professional toolbox of progressive lens
designs?
First, the progressive must meet
the physiological needs of the patient i.e., deliver binocularity, excellent
acuity and wide clear comfortable fields of view at all distances that the
patient will use them. In addition, the lens materials must be protective and
comfortable so the patient is assured of healthy sight and wear their glasses
as prescribed to operate at peak visual performance.
So, what is the best way to
choose a progressive lens?
THE CURRENT NORM
Todays common progressive
technologies allow almost any manufacturer to produce a progressive design that
will work. Of course, some work more effectively than others. As evidence,
think of the last time there was a true nonadapt in your practice. In fact,
most of the warranty redos today are for Rx and/or fitting height changes.
Therefore, to separate oneself
from the current norm, the future lies in really perfecting a wearers vision
and seamlessly meeting their comfort needs at all distances in the best variety
of materials and treatments. This requires new techniques and technologies that
mirror the physiology of vision and materials and treatments that promote
healthy sight.
PATIENT EXPECTATIONS
Patients want and expect the best
vision and will purchase something professionally recommended as being the best
for them. The right progressive grows a practice even if it is more expensive
for patients. It is the success of the result that matters more than the
initial price. Remember, a patient will wear these lenses for two to two and a
half years. So, on a daily basis there is little difference in cost.
For example, in most offices,
using better AR lenses improved patient satisfaction and grew AR sales, even
when these lenses were a higher average selling price. The reason is the
product met the claimed performance, had few post-dispensing problems and
continued to deliver peak performance for the life of the prescription. Think
of the introduction of Crizal Aliz over standard Crizal or how other improved
AR lenses replaced their previous versions.
The same is true for new lenses
that improve visual performance over previous lenses dispensed. Small
improvements are noticeable by wearers because overall vision is made better
and large improvements to particular lens portions better meet a wearers
needs. Finally, these attributes must be delivered reliably and consistently to
all patients regardless of prescription. Exceed your patients expectations;
both visually and fashionably, know how to describe the benefits and your
practice will succeed.
EYE PHYSIOLOGY AFFECTS VISION
Typically, the refraction part of
the eye exam has determined the binocular and prescription needs of the patient
i.e., the centering, prism and prescription values from which lenses are
created. In terms of their effects on vision, these represent the first
(binocularity) and second order effects (defocus in each of the principal
meridians). This should result in a properly centered Rx with the correct
sphere, cylinder and axis values as well as any prescribed prism required for
the patient. However, even with the best refraction, some patients still see
better with one eye than the other or vision is not as clear as the patient
would like it to be.
This reduction in crispness may
be due to other aberrational effects contributed by the shape of the cornea and
internal structures of the eye. An example of this would be the way water
reflects the scene below. The reflection is blurred and/or distorted from the
lack of smoothness of the surface. If there are these kinds of localized
inconsistencies in the eye system, the result is less than clear vision. To
improve sight, one must be able to consider these effects and the methods that
can be used to create a spectacle lens to globally correct them. In addition,
indirect light can further reduce straight ahead vision and that too should be
modified.
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| An uneven
water surface blurs and distorts the image of the trees. Uneven surfaces or
irregularities in the eye system reduce the quality of vision. Two eyes that
see 20/20 may not have the same quality of vision. |
In this case, an analysis of the
third order effects of astigmatism, spherical aberration and coma using larger
bundles of rays, over smaller and more distinct areas of the lens, creates a
full field wavefront that better quantifies image quality. Using this method to
alter the progressive surface and the resulting wavefront can improve the
unevenness of the image and a patients quality of vision. Analysis of the
effects of the total eye system on the wavefront and applying it to lens
surface design is called Wavefront Advanced Vision Enhancement or W.A.V.E.
technology.
W.A.V.E.TECHNOLOGY AND DIGITAL
SURFACING
W.A.V.E.Technology applied to
lens design and the use of digital surfacing to create molds provides the
precision to improve vision clarity in progressive lenses over previous
technologies. How is this accomplished?
Use previous progressive design
and wearer experiences as well as better computing power and mathematics to
analyze the effects of a larger bundle of light on small areas of a progressive
surface; Essilor vision scientists specified a new surface shape for a new
progressive series called Varilux Physio. This new lens produces better vision
than previous Varilux lenses.
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Not
just a ray but a larger bundle of light, pupil size.
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More
individual areas are considered. |
More
reliable prescription production over more of the lens surface. |
NEW VARILUX PHYSIO PROGRESSIVES
New Varilux Physio improves
vision sharpness and overall visual field clarity. Previously, progressives
were most often described in terms of the distance, mid-range, near and
peripheral viewing zones. This was because the zones were bordered by more
distinct areas of blur and required patients to learn new vision behavior.
However, when the awareness of the boundaries are removed because the blur and
its effects are significantly reduced, there is more of a sense of freedom that
is expressed by wearers as: I see better. The overall field is clearer.
This is accomplished by better
managing how off axis astigmatism and coma affect overall vision. In both cases
they produce blur but are slightly different in shape and effect. A reduction
in the magnitude of off-axis astigmatism (blur) bordering the distance and
intermediate logically increases the clear field of view. This is especially
important for the variety of prescriptions that any office receives.
For example, some patients
comment they see differently when looking to the right and left through their
progressives. When creating a progressive surface, lenses steepen toward the
bottom so the vertical curve changes faster than the horizontal one. The result
is astigmatism or blur. Where this is located affects the impression of how
clearly patients see through their lenses.
Peripheral vision clarity, across
the distance and mid-range band is a combination of the front surface design
(cyl and axis) and the prescription of the wearer (a different cyl and axis).
In older progressive designs, the difference in peripheral vision may be
noticed. Physio better controls the effects of the front surface i.e., reducing
the amount of surface astigmatism and ensuring a more upright orientation, the
resulting vision across the distance and midrange band is now clearer. For the
patient, the experience is one of a wider, clearer overall field of view. Coma,
a comet shaped blur that causes images to flare, affects off-center acuity and
further blurs the edges of the object reducing contrast. Reducing coma improves
the visual experience. This improvement can be seen especially around lights at
night since the pupil is larger. As a result, vision is clearer because there
is less aberration and an improvement to contrast. Remember, vision is better
if acuity and contrast sensitivity is enhanced.
To further improve
vision in the mid-range band, adjustment of the orientation of the astigmatism
bordering the corridor can widen the usable field. If more vertical, vision is
clearer and the usable field of view is wider.
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The
amount of surface astigmatism is reduced and made more vertical for a wider
filed of clear vision.
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Lastly, the orientation and
location of the near zone is correctly placed in the lens respecting the
prismatic effects of the wearers distance prescription. Horizontal prism
changes the amount that myopes, emmetropes and hyperopes converge so the near
is centered taking this into consideration. Myopes converge less than
emmetropes and conversely hyper-opes converge more. As a result, there is
variable inset in the lenses to place the near where the patient looks.
Vertically, the wearer wants
reading with the least effort. That means without extreme posture changes to
find the right power. This is especially true in older presbyopes. Therefore,
reading is controlled vertically and at the correct inset angle to improve
reading comfort.
Therefore, to provide a patient a
better and in fact, a more natural vision experience, the distinction between
progressives zones must disappear. Increasing the size of the distance by
better aberration and astigmatism control, ensuring smoother vision through the
boundaries, better orientation control of the axis across the intermediate
field of vision to the horizontal and vertical position of the near makes a
better performing progressive lens design.
PRECISION WITH DIGITAL SURFACING
Digital Surfacing provides the
precision control required to replicate the required changes to the Varilux
Physio design surface. Molds for casting plastic lenses or molding
polycarbonate are made in a variety of ways. Most commonly, molds are produced
by slumping or producing electroforms from slumped masters. In both methods, a
ceramic former (convex progressive surface) is cut and a glass plate is placed
over this former in an oven. Once heated to about 700 degrees, it slumps to
approximate the surface of the former. This concave shape will then be used to
cast progressive fronts on semi-finished lens blanks. The flow of the melting
glass can produce imprecision in surface creation. The slumping process has
limited the ability of lens designers to convey certain design elements to a
finished progressive power lens.
Multi-axis and surface height
cutting control, digitally directed, creates molds for surfaces that provide
the precision to improve vision clarity in lenses. A mathematical description
of the W.A.V.E. constructed surface drives newly designed and modified
multi-axis lens generators to create mold surfaces by single point diamond
turning. If small front surface corrections can be meaningful to wearers,
further optimization of vision can be added to the back surface of lenses as
the distance prescription is added to the lens.
| Direct surfacing |
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Single
point diamond turning is one of the free form methods used to create smooth
complex surfaces. A good design is first required before the advantages of this
equipment can be realized. |
ENHANCING VARILUX PHYSIO VARILUX
PHYSIO 360
In Varilux Physio 360, the
patients lenses are further improved by optimizing distance and reducing
aberrations using a Varilux Physio front and digitally adjusting the back
surface. The prescription and an optimization to reduce the effects of the
front surface astigmatism are individually created on the lens rear surface.
In this way the progressive is personalized to further improve acuity and
contrast. Who benefits from this kind of lens?
Consider the earlier discussion
that different Rxs affect the through power of lenses peripherally and
therefore the vision of the wearer. If one could neutralize part or all of the
effective errors created, the patient could have further improved acuity and
contrast. In addition, consider that patients prescribed higher cylinders i.e.,
cyls over 1.75D. In these patients, the high cylinder means that the two powers
in each of the principal meridians would warrant a different base curve. Since
all patients in that range get the same base, the high cyl wearer is somewhat
disadvantaged.
In a Varilux Physio 360, the
back surface of the lens has small changes integrated seamlessly to maximize
vision potential.
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Plano/+2.00Add
The size of clear viewing zones can be predicted for a plano distance lens.
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However,
any cylinder Rx can alter the size, shape and orientation of clear viewing. By
making small digital changes to the ocular surface, the effects of the cylinder
on the design of the lens can be minimized and each meridian can be better
improved in acuity, contrast and width of clear field of view.
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Optimized
surfaces restore the intended design over a large range of prescriptions.
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Using Varilux Physio 360 better
meets wearers expectations; patients who want the best, patients with high
prescriptions, those who want maximum size of available fields of vision or
those who have not adapted to other progressives.
FURTHER ENHANCE FUNCTIONALITY
Physiologically fitting
progressives requires that the functionality of the lens is also addressed.
Enhancing the functionality of a good design further enhances vision. Remove
all glare, protect the eyes, improve durability, use photochromics for the
ultimate in versatility and comfort, and use products whose brand identity
meets your professional identity.
Remove all glare Glare
causes squinting and fatigue, blocks sight and changes colors. Ask patients how
glare bothers them, demonstrate AR, tints, photochromics and polarized. Reduce
or eliminate glare for better vision. Confirm a patients preference.
Protect the eyes Healthy
sight requires 100 percent UV protection. Use polycarbonate, Trivex and all
indices from 1.6 to 1.74 or ask your lab to UV dye plastic. All photochromics
and polarized lenses also absorb 100 percent of the UV. Consider materials of
increased impact resistance when the patients lifestyle demands it.
Healthy Sight
Counseling
Transitions
Optical provides a series of guidelines called Healthy Sight Counseling that is
consistent with dispensing both the best in vision and the best in eyecare.
Healthy Sight Counseling is an integrated approach that allows eyecare
professionals to promote healthy sight in their practices so patients can
maintain overall quality of vision and preserve their long-term ocular health.
Healthy Sight Counseling can be achieved through a combination of vision care
(maintenance and preventive eyecare), vision wear (customized vision
correction) and education (increased professional and patient awareness).
Vision wear
includes the assessment of vision and the determination of the refractive
error. Once the best corrected visual acuity has been determined through
refraction, the task of the ECP is to use the history to address the quality of
vision areas that will ultimately determine how satisfied the patient will be
with the eyeglasses prescribed. Vision wear and customized vision correction
are consistent with the Physio technology in improving acuity. Its delivery in
a lens material further addresses the concerns about eye health.
Understanding the
patients visual lifestyle is key in dispensing corrective eyewear. These
involve occupational, recreational and social requirements. Lifestyle
dispensing can be taken a step further with lifestyle prescribing. To provide a
customized eyeglass prescription, lifestyle prescribing takes visual lifestyle
and visual health into consideration. This allows customized vision
correction and provides the best in vision wear, while promoting healthy sight
and long-term ocular health.
In achieving
healthy sight for patients, quantity of vision (Snellen acuity) and quality of
vision (contrast sensitivity and glare acuity) should be measured. Its
important to look beyond the numbers when prescribing and recommending lens
design and enhancements that will specifically address each patients needs.
Photochromic
lenses block ultraviolet radiation (UVR) and modulate light depending upon the
level of UVR; offering enhanced visual protection, visual quality, visual
comfort and automatic convenience under varying light conditions.All lenses
should block UVR and meet internationally accepted standards such as ANSI, ISO,
AS/NZS and EN. Other lens enhancements include AR coatings, polarized
protection and impact protection. For more information about this program,
visit www.transitions.com.
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Varilux Physio
and Other Varilux Fitting Tips
Step 1ADJUST THE
FRAME
Make
sure the frame is properly adjusted on the patient before taking any
measurements. Set the vertex distance between 12 and 14 mm and the pantoscopic
tilt angle between 8 and 12 degrees. The frame should have positive facial
wrap.
Step 2TAKE THE
PATIENTS INTERPUPILLARY DISTANCE (PD)
Exact
alignment of the lens, beginning with an accurate PD, is a must for far and
near vision.
To ensure maximum
accuracy, use a Corneal Reflect Pupillometer, which obtains both binocular and
monocular PD in a single procedure. Use one measurement to verify the other:The
monocular PD, when added together, must equal the binocular PD. If not, new
measurements should be taken.
Step 3TAKE
FITTING HEIGHT MEASUREMENT
Accurate vertical positioning is important. In an adjusted frame, a lens
positioned too high or too low may limit the field of vision as the eye moves.
To deliver uninterrupted power change and to ensure comfortable near vision,
follow the recommended minimum fitting height. If the selected frame does not
accommodate this height, edging may remove a valuable portion of the usable
reading area.
Take a monocular
height measurement by marking each lens at pupil center using a felt-tip pen.
Draw a horizontal line on each lens and verify the lines are crossing the
center of each pupil.
If the
measurement was taken at the dispensing table, ask the patient to stand and
fixate on an object in the distance. Observe the positioning of the horizontal
line to be sure it intersects the pupil.
Check the fitting
height by measuring from the deepest point of the lens to the pupil center. Be
sure to be at the same level as the patient to avoid parallax error.
Step 4CHECK LENS
CUTOUT
Double check fit. Mark the patients fitting height and PD on the sample lens,
creating a cross. Place the lens cross over layout chart cross to verify that
the lens will cut out. If it doesnt fit, choose another, more suitable frame.
An important
reminder: To provide comfortable near-vision, its neither necessary nor
recommended to increase the add power of a Varilux PAL
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Guarantee versatility and comfort
Consider any higher index Transitions to significantly improve fade back time
over plastic photochromics and improve thinness and lightness in photochromics
by using the specialty poly-carbonate and thinner and lighter 1.60 and 1.67
lens materials.
Meet what patients consider the
most important attribute of eyewear lightness and comfort. Always
suggest materials thinner and lighter than ordinary plastic. Match physical
comfort with visual comfort.
Promote brands that promote your
identity No other product has the consumer awareness of Transitions.
Use its brand identity to enhance the professional identity of your practice.
Always consider brands that support and grow your profession.
POSITIONING VARILUX PHYSIO IN YOUR
PRACTICE
Reducing the number of
progressive choices is healthy for any office. Varilux Physio is uniquely
usable by virtually all patients, it simplifies progressive lens choices, can
be further optimized by ocular side digital surfacing and when married with the
benefits of a variety of materials and treatments, it faithfully delivers
healthy sight. All while it helps to differentiate the practice.
Create scripts for staff for
success. Develop a concise series of words that describes the opportunities and
options, their benefits and costs, so staff delivers a consistent message.
Unlike other progressives, new
Varilux Physio considers the more complex components of vision errors, using a
set of newly developed tools, to better correct sight in all the ways that
patients wear progressives.
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