Eyeglasses.com Blog

Articles for April, 2009

Navigating the Lens Material Landscape

01-2009



Navigating the many lens materials now available is made much easier when you use the common denominator of standard plastic to chart your course. This article offers a quick and easy method to locate the best material-of-choice for every patient. A two-digit multiplier is used to guide you when filling patient Rxs within the +10 to -10 diopter range. This simple and clinically practical technique will help you achieve patient-pleasing eyewear designs every time.

As a consultant for a large lab, the eyewear problems that I encounter have usually been screened by highly experienced prescribers and dispensers. Issues such as regret about the frame selected, cost and problems that can be resolved by simple re-measurement or realignment have typically been addressed before the questions reach me.

Several years ago I realized the single most common “not-happy-with-new-eyewear” problem that reaches my desk is related to an inappropriate choice of lens material. In fact, this led me to suggest an easy-to-use benchmarking to help practitioners navigate through the many indices that are available today. For a detailed discussion of this, please refer to “A Rosetta Stone for Eyecare, Decoding the Issues of Index,” which appeared in the March, 2007 issue of 20/20. Below we delve into how using a Curve Variation Factor (CVF) can help you decide whether increasing the index is a good choice for your patients.

Why Change the Index
The most common beliefs for moving a patient to a higher-index material include the lenses will be thinner, the lenses will be lighter, the lenses will be less curved and the lenses will perform better optically. The thinner, lighter and less curvature reasons are based on physics and fact. The myth that higher-index lenses perform better optically probably persists because of their relative newness to the market,their status as a “premium product” and their higher cost. The most patient-troubling aspects of higher index are related to high reflectance and low Abbe values (i.e. greater chromatic aberration). Fortunately the portion of the reduced optical performance caused by higher reflectance is much reduced by AR, so practitioners who use AR encounter relatively fewer problems with increased index.

Reasons for avoiding higher-index materials can include: More problems with night driving, more veiling glare during daylight hours, reduced lens performance related to low Abbe values and higher cost (especially when there is little or no patient-perceptible improvement in either appearance or performance).

When the power of a lens is not the same for all colors of light, the lens has chromatic aberration. The Abbe value tells how much chromatic aberration is present. A high Abbe value means less chromatic aberration and a low Abbe value means more is present. Chromatic aberration causes images formed by white light (multi-wavelength light) to be more (i.e. lower Abbe) or less (i.e. higher Abbe) out of focus. When the patient is looking through the optical center of the lens, you can think of the red end of the spectrum and of the blue end of the spectrum as being slightly “underfocused” or “overfocused” relative to the yellow-green bling when the line of sight passes through the optical center of the lens because the slightly out-of-focus wavelengths are centered on the yellow-green, in-focus image. When prism is introduced the situation becomes more troublesome because the various color components are shifting differing amounts to the side or up or down, causing color fringes to become visible.

Patients, especially those in the intermediate prescription ranges who are accustomed to using peripheral areas of their lenses, tend to be more susceptible to problems of low Abbe values. For these patients especially, try to use the smallest possible eye size and avoid large amounts of decentration if possible when you must use a higher-index material. Patients with prism prescriptions are also more troubled by low Abbe values because the multi-wavelength images are shifted further along the base-apex line of the prism. There is no practical way to eliminate chromatic aberration in spectacle lenses, but using AR makes patients more tolerant of the problem.

The issue of increasing the index is a more slippery slope. If the eyesize is about the same and if the prescription is not greatly changed, the patient can compare the old lenses with the new. The question is, will the new lenses be perceptibly thinner and lighter than the old ones. Even more important, is the difference of a magnitude the patient will appreciate and is that difference a fair value considering the additional cost?

The simple multipliers (CVFs) presented in the “Rosetta Stone for Eyecare” are your key to finding your way to the best material choice for your patient. The multipliers for the most common indices are given in Fig. 1. For clinical purposes you can simply multiply the power in the strongest meridian of the patient’s Rx by the multiplier for the material you are considering. You then easily compare the power in the strongest meridian in standard plastic with the result of your multiplication and use your clinical judgment to decide if the change to a higher index would be meaningful for your patient.

Example 1: Your patient’s prescription is -8.00 -2.00 x 090 in both eyes. The power in the strongest meridian in this prescription is -10.00. You have managed to find a frame that is cosmetically and functionally acceptable. Its size is 48-18, so the frame PD is 66mm. Your patient’s PD is 65mm so you will only have 0.5mm decentration in each eye. The mounting line falls at the base of the patient’s pupils in the straight ahead, level gaze position. With minimal decentration and an MRP placement just halfway from the top to the bottom of the lens you have an eyewear design that is advantageous for this prescription. The question now is whether you should opt for reduced optical performance of a mid- or high- index lens to further reduce thickness, curvature and weight of the finished lenses. You must also select the amount to increase the index.

Since you are very familiar with standard plastic you have a pretty good idea of how thick a 48mm lens would be in a 1.49 material. If you consider poly for this patient you would multiply the -10.00 by .85. The result, -8.50, is the power of a standard plastic lens that would have the same volume and thickness as your patient’s -10.00. Better yet, poly can be surfaced 1.0mm thinner all the way across, meaning that your edge thickness would be 1.0mm thinner than a -8.50 in standard plastic. If you consider 1.60, the multiplier is .83, and the resultant lens would be the equivalent of a -8.30 in standard plastic. If you go to 1.70 the multiplier is .71 so the resultant would be close to the curvature and volume of a -7.00 in a standard plastic.

For most patients you would not want to have the 7.8mm edge thicknesses of 1.49 material, but would poly, at about a 5.7mm edge thickness, be enough of a thickness reduction?  A 1.70 index lens would give about a 4.9mm edge, but of course the higher the index, the greater the cost and the greater the reduction in optical performance. The edge thicknesses above assume a 2.0 CT for standard plastic and a 1.0 CT for poly, 1.60 and 1.70 materials.

Example 2:  If the patient’s strongest meridian is only -5.00 instead of -10.00, going to a poly (.85 x -5.00) would give a resultant of -4.25.  Even with the additional reduction of 1mm due to poly’s break resistance, do you think your patient would perceive and appreciate the equivalent of a 0.75 drop in power?

In the case of a larger eyesize the reduction in thickness yielded by going to a higher-index material is naturally greater. On the other hand the chromatic aberration problems related to a low Abbe value is more troubling to patients who are eye-turners rather than head-turners (i.e. usually those who have lower rather than higher Rxs) and the problems of a low Abbe are more apparent to patients who can turn their line-of-sight further from the distance MRP (e.g. when ? 2mm of decentration is needed in each lens).


Patient  Tolerance
Patient tolerance is hard to quantify, but every successful dispenser develops a sixth sense about it. In the exam room highly sensitive (i.e. low tolerance) patients may be acutely aware of 0.12 diopters of blur, or a shift of a very few degrees in a cylinder of as little as 0.50 diopter. They may be excruciatingly exact in trying to perform even the simplest of subjective tests. Sometimes this is called the “Princess and the Pea” phenomenon. There are surely combinations of physiological and psychological reasons that cause some patients to have low tolerance, while others can tolerate or adapt to a surprisingly wide range of power, magnification, transmittance and weight combinations.

If careful frame selection eliminates thickness and weight sufficiently, you should use that to your patient’s advantage and avoid increasing the index of their lenses.  Aspheric lenses may be an alternative to a large increase in index for a patient who wants thinner lenses since using an aspheric design sometimes allows a more moderate increase in index. Increasing the index should be a court-of-last resort decision once you have explored other alternatives. Transforming lens prescriptions into finished eyewear requires science, art and judgment. Today’s excellent higher index materials offer advantages to patients above +4.50 to +5.00 Rxs, especially with large lens sizes, but they should be used with careful consideration if you want the eyewear you design to be truly patient-pleasing. Reprinted with permission from Jobson Publishing.

Debunking Myths about Abbe value

02-2009





Can millions of polycarbonate and high-index plastic lens wearers all be wrong? In a lens market that consists of approximately 59 percent high-index (40 percent polycarbonate with an additional mix of 11 percent other materials, such as 1.60,1.67,1.74 according to the Vision Council of America) is it possible that all those wearers just don’t realize how badly they see due to their poorly performing lenses. It’s doubtful.

 

For years, that is the unlikely scenario the opponents of polycarbonate have been proposing under the banner of “blurry by reason of low Abbe value.” The fact of the matter is that Abbe-based criticism is mostly the result of marketing exaggeration as opposed to actual performance problems. After all, if Abbe value is the critical link to clear vision, then why is glass, with it’s high Abbe value relegated to a mere 1 percent usage while standard plastic, with a relatively high Abbe value of 58, is dropping like a rock in overall lens sales?

HISTORY
Back in the mid ’80s when our industry was demanding a high-index plastic the best product available to mainstream dispensers was what we today call, mid index, a very non-glamorous 1.54 to 1.56 material. Major manufacturers did not carry polycarbonate as it was a niche material used only for safety eyewear. When dispensers saw the benefits of a 1.59 index they embraced it for their dress wear customers. Polycarbonate was thinner, lighter, safer, more scratch, UV and impact  resistant than the mid-index materials offered by the major manufacturers. As a result the sales of mid high-index languished. In an effort to jump start their mid-index product manufacturers who did not carry polycarbonate grabbed hold of Abbe value, the only area where there material had an edge, and evolved the myth that Abbe value was the holy grail of clear vision. They did that by stretching a few facts that measured an inch—into a mile. Yes it is true that lower Abbe values indicate greater dispersion and greater dispersion leads to less clarity, but the area always left out of that logical pursuit is that the point on the lens at which the chromatic aberration is significant enough to create a visual problem is the point through which the wearer does not normally look. In order to feel comfortable with polycarbonate today we should confirm the areas that have been a problem and illustrate how those areas have been corrected with today’s product.

The optical business has, traditionally, gone outside of itself to find technology that is close but not specific to its needs. The result of this is that the early versions of the optical product created with this new technology often fall short of it’s original promise. A period of growth or a learning curve must be implemented. The theory of polycarbonate for lenses was good but the reality of what we were able to produce fell short. Lenses lacked clarity. Availability was very limited. Manufacturers had problems producing lenses. Labs had problems processing lenses. Dispensers did not know how to position and present polycarbonate. Outside of our industry the material was used mostly in the protective equipment industry. The purity of the material was not of critical importance. In the optical industry purity was of key importance, but since our usage of the raw material was so low suppliers refused to go to the expense of purifying the product to meet such a small market demand. The result was that lenses made from an impure raw material yielded an inferior lens. The best stereo system when played through the worst speakers sounds bad. It was not until the computer and recording industry selected polycarbonate as their potential material of choice for their new CD technology that the makers of the raw materiel found it economically feasible to purify their product. The result was that the demands of other industries yielded the pure product that the optical industry enjoys today. In the beginning the product was hampered by a marketing failure. While the product was promoted as a high-index plastic appropriate for high-minus and high-plus Rxs, the only real availability was in the range of a 4 to 6 base curve. This made the actual deliverability of higher powered Rx’s impossible. Many early prescriptions that needed steeper or flatter corrected curves were forced into the middle of the road curves available. A lot of prescriptions were ground on the wrong base curve, people hated the resulting poor optics and the blame wrongly went to the material.  We had the promise of high powered solutions with middle of the road availability. Due to the fact that polycarbonate makes a great package of benefits to the wearer, demand for the product has increased dramatically.  As a consequence there are many major manufacturers offering a wide range of product offerings. Dispensers now feel more comfortable offering poly to their patients. Regardless of lens design, base curve, or enhancement options the majority of prescriptions may be readily filled. The momentum is established and the growth for the future is positive.

 

PROCESSING
There have been major improvements in the processing of polycarbonate and high-index. As a result the blanks being produced today start off without the built in stress and aberrations that were commonplace in the original products. The original polycarbonate coating was a dip process that left an uneven surface. Run off lines around the segments were common. The hard coating was not well matched to the relatively soft polycarbonate substrate. As a result, cracking and separation were common. Patient satisfaction with these limitations was a problem. The coatings that are being used today are of a very high quality.

• Run off at seg lines is no longer an issue.
• There is some tintability. (Do not oversell this, because tinting at all densities is still not possible.)
• The performance of the coating is much improved.
• Flexibility allows for a better long term bond to the surface.
• The hardness of the new coating is outstanding for surface protection. 

Since this technology came to us from outside our industry it was expected that a learning curve would have to be satisfied. Laboratories struggled as they tried to apply state-of-the-art methods used to process standard plastic (i.e. CR-39 monomer from PPG Industries) to a completely different material. Generating, fining, polishing and edging all posed great difficulties to the lab. As a result “breakage” was the word of the day and long delays discouraged the use of polycarbonate. In fact these problems were so severe that memory of those days continues to cause the rejection of this material in some form even today. Polycarbonate material was much more sensitive to heat than standard plastic. As a result labs had a lot of problems with waves and aberrations due to excessive heat build up in the blocking, generating, and edging process. Unlike standard plastic, which ground off cleanly, this thermoplastic material had a tendency to melt and leave very uneven surfaces when ground in the traditional way. All grinding and edging on standard plastic was done with a coolant wetted surface; however, polycarbonate responded better to dry grinding. Dry grinding created the problem of excessive heat. It became apparent that all new technology and equipment would be needed to process the material effectively. It took years for the industry to improve its equipment and even at that not all labs had the benefit of the latest technology. Due to the disparity of a unified approach there came a period where some labs distinguished themselves with good performance in poly while other labs, slow to change, helped to impede poly’s reputation with poor turn times and bad quality. Through the efforts of leading manufacturers and groups like the Optical Laboratories Association and the Polycarbonate Council, new equipment and methods have been pioneered to address all of the issues that troubled polycarbonate. As a result the material is on firm footing today and growing every year.


ABBE MYTH AND CLEAR VISION
Referring back to the basics it should be understood that an optical prism will bend white light towards its base. White light is a combination of all colors, and the degree to which the light is bent is proportional to the wavelength of the color. The shorter higher energy wavelengths are bent more readily and to a greater degree than the longer lower energy wavelengths. This phenomenon is responsible for the dispersion of white light through a prism into its component parts. The lens designer must deal with this aberration by selecting a lens material with a low dispersive value (Abbe Value). Since lenses are a combination of prisms this uneven bending of the various wavelengths results in separate focal points. This will manifest itself to the wearer as blur. The following diagram illustrates the two focal points formed by the violet and red wavelengths refracted by a spectacle lens.

Chromatic aberration is not an issue for straight ahead viewing. Only off-axis gaze is affected by chromatic aberration.

Clinical Studies Show:
In near vision 100 percent of the gaze fixations are less than 10 degrees ( 5mm to either side )
In distance viewing 80 percent of the eye movements are less than 30 degrees ( 7.5 mm to either side )

Most prescriptions will not generate enough aberration to be troublesome in the normal range of vision. The reactions of wearers have been found to be subjective and variable. In static vision, the angle of gaze has to be greater than or equal to 30 degrees (15 mm to one side ), before there is an effect on most wearers. In real life when people perceive something outside of 8 to 10 mm from lens center, they automatically turn their heads. Thus they never leave the central portion of the lens.

 

A discussion of lens materials usually includes the material’s Abbe number. The number ranges somewhere between 20 and 60. Higher numbers have less chromatic dispersion. An arithmetic value between 1 and 100 derived as the reciprocal of the relative dispersion of a refracting medium; the closer the Abbe number is to 100 the more efficient the refractive medium. On paper the matter of chromatic aberration is real: however, in practice it is not the factor that Abbe bashers make it out to be. Abbe is not a factor in low or medium powers. It can be a factor when powers or gaze angles are extreme.

Unfortunately dispensers often take the path of least resistance. When problems of clarity arise the first area blamed is the Abbe number. In reality there are often other more primary factors that contribute to the loss of clear vision most notably poor light transmission due to the absence of anti reflection and using a non aspheric lens design.


 

Anti-Reflective Lenses

    Standard Plastic ( 58 abbe) = reflect 7.94%

    Poly (31 abbe) = reflect 10.26%

    1.67 (32 abbe) = reflect 12.32%

    1.74 (33 abbe ) = reflect 14.58%

This chart compares the visual acuity of standard plastic and aspheric polycarbonate at different angles of gaze. Across the bottom of the chart we have different angles of gaze -- to the right and left. The acuity measurement is the vertical scale in the middle of the chart. It is measured in LogMar, which means, in simple terms, for every increase of .1 on the LogMar scale, visual acuity decreases by one line on an acuity chart. In the red you can see the performance of a standard plastic. The optical quality of standard plastic, in any prescription, is seldom called into question. In blue, you can see the performance of polycarbonate often accused of visual acuity. Remembering that we just said about 80 percent of all gazes are within 20 degrees in either direction. At 20 degrees in either direction, the visual acuity of aspheric polycarbonate is equal to that of standard plastic. Outside 20 degrees in the off axis viewing zone aspheric polycarbonate actually out performs its higher abbe plastic competitor.

There are certain facts that are often misunderstood and frequently misstated regarding lens material qualities, in particular, Abbe value, and its’ impact on optical performance. The effect and importance Abbe value, is often stated as the beginning and end of an acuity performance issue, but in reality the Abbe value is just one factor that should trail in only after dealing with the more significant design issues. By optimizing the lens material with aspheric designs and anti reflection— Abbe value and other qualities of materials become minimal issues. There can be a number of factors that cause a patient discomfort. In many cases more than one factor may be present to cause a problem. If one of the problems can be addressed that may be enough to put the person back under their threshold of rejection. Let’s take what we have learned regarding gaze angle and link it to visual acuity. If optimized aspheric designs and anti reflection are built into a lens its Abbe value is of little concern.

If a tree falls in a forest but there is no one there to hear it—is there a noise. That is an interesting philosophical question that we will probably never have the answer for. On the other hand if there is chromatic aberration at a point on a lens where no one looks—is there a problem with optical clarity? Now that is a question that millions of polycarbonate and other high-index lens lens wearers have already answered, and the answer is: NO. Reprinted with permission from Jobson Publishing.

Avoid that complaint with creative eyewear solutions

03-2009


Photograph by Black Box Studio

By Palmer R. Cook, OD

We all want our patients to be pleased with their appearance in new eyewear, yet the end results do not always meet our expectations. Since eyewear covers 25 percent or more of the face and masks the most expressive part of our appearance, our eyes, is it any wonder people are sensitive to the way they look in new eyewear? Your challenge is to give patients the best combination of “looking good” as well as “seeing well” in new eyewear. Experience and intuition can lead to good cosmetic results, but there are also some important guidelines to help you achieve a “look” that patients will appreciate without sacrificing eyewear performance.

The four attributes of lenses that most affect appearance are: edge thickness, magnification/minification, curvature and reflectance.

Edge  Thickness
Lenses with thick edges, especially lateral edges of about 5mm or more, tend to attract attention and detract from good appearance. Usually minus lenses are considered when edge thickness is discussed, but occasionally stock plus uncuts are edged down for small eyesizes and this leaves the patient with unnecessarily thick and heavy lenses.

Clinical Tip: For moderate to strong plus prescriptions that are to be mounted in small eyesizes, insist that the lab surface the lenses rather than using uncuts to avoid the weight, magnification and thickness issues.

To reduce edge thickness in minus lenses, strive for little or no decentration, smaller eyesizes, materials that can be surfaced thinner such as Trivex or poly, and consider using aspheric designs. Using a higher index material to decrease thickness is most effective over about 5 diopters of power and when designs with larger effective diameters must be used. The effective diameter of any lens shape is the distance from the center of the lens to the furthest edge.

Clinical Tip: As the power of the prescription becomes greater, the lens shape that will give the best cosmetic results will usually become closer to a circle or an oval. (See Figure 1)

Magnification/Minification
The amount of magnification (or minification in the case of minus lenses) has relatively little detrimental effect on the appearance of eyewear except in very strong powers and when the phenomenon of facial inset occurs with minus lenses.

Facial inset is the inward displacement of the face due to the minification effect of minus lenses. It is worse with longer vertex distances and it is directly related to the amount of base out prism in the lateral periphery of the lens. Facial outset is the outward displacement of the face due to the magnification of plus lenses and it is also worse with longer vertex differences. It is most noticeable when patients turn their heads a few degrees to the right or left.

Facial outset is still relatively rare, but since high-plus lens can be made thinner and lighter it is becoming more common. Facial outset can be seen in the classic movie “A Christmas Story,” where the main character, Ralphie, wears a moderate plus lens correction. Ralphie’s eyewear is, as it should be, about as wide as the widest part of his face. Because of this when he is looking directly into the camera the facial outset is not apparent. When the camera shot passes through the lens lateral to the optical center and on to the edge of Ralphie’s face the facial outset is apparent. The effect would be much greater if the lenses were a higher plus power and/or if the lenses were wider, especially if they extended wider than his face.

Facial outset was largely avoided in the past because dispensers were sensitive to the excessive center thickness and weight increase caused by fitting high-plus lenses into large eyesizes. Now high-index lenses and aspheric lens designs permit the design of larger lenses in the high-plus powers without the massive increases in thickness and weight of the past. Even though new technology makes it possible to use larger lenses for hyperopic patients, the increase in size should be done with moderation.

Facial inset is most apparent when viewed from directly in front of the patient and facial outset is usually most apparent when viewed at a somewhat oblique angle.

Clinical Tip: Facial inset and outset problems cannot be completely eliminated, so you may wish to caution patients that when they are photographed the camera position should be carefully chosen. Because both inset and outset problems are related to the amount of prism in the lateral periphery of the lens, it is important to use a frame that requires little or no decentration. Also the eyesize of the frame should be kept as small as practical. Some wrap can be induced when fitting the frame to further reduce these problems, but it is important to make the same modifications to power and Rx PD that you would make with any wrap frame. In very high powers only minimal amounts of wrap are practical.

Curvature
Corrected curve lenses were developed to give better optics when the line of sight passes peripherally through the lens. Aspheric lens designs are used to reduce peripheral aberrations even though a flatter lens design is used. Typically, flatter, aspheric lens designs have thinner edges and shortened vertex distances. This improves appearance and widens corridors and reading areas for PAL lenses. The most cosmetically undesirable effect of flattened curvatures is related to front surface reflections. Curved reflecting surfaces make light sources smaller and visible over a wide viewing angle. Flat reflecting surfaces do not minify the image of the light sources they reflect and are visible at a “direct bounce” angle. Occasionally movie directors put evil characters in lenses with plano front curves. They then bounce light from the lenses into the camera to obscure the actor’s eyes and make him more threatening at strategic moments. Since the wider use of high-index, aspheric lenses, this effect can be seen more frequently among commentators, experts, political pundits and newscasters on TV. For patients with these kinds of duties, excessive flattening of the base curve may not be a good choice.

Reflectance
The use of anti-reflective lenses improves performance and appearance. Performance issues aside, the use of AR makes eyes more visible, eliminates the “glassy” appearance of mid- and high-index materials, and it makes the lenses less visible. It can almost be like removing the lenses but leaving the prescription in place. AR also reduces the prominence of the “bulls-eye rings” of myopia. It should be remembered that every problem related to reflected light is reduced by the use of anti-reflective lenses. This is true for every lens material and every prescription, although the benefits of AR are exponentially greater for higher index materials. 

The color, shape, size and design of the frame also affect the finished appearance of your patient’s eyewear. Carefully selecting the right combination of each is important. Sometimes patients “economize” by trying to make one frame meet all of their eyewear needs. Results of this “averaging” are, at best, average from both a performance standpoint, as well as in terms of appearance. Most patients have specialized sports footwear, work footwear and several choices of dress footwear. You may want to point out that trying to make one design do everything is even more futile with eyewear than it is with footwear. 

Color
The patient’s complexion and wardrobe preferences should always be considered when selecting the material and color of the frame. Style conscious patients will usually be able to make appropriate choices in color and texture of frame materials. You should have sample lenses available to demonstrate and compare the various colors of AR with both patient complexions and possible frame choices. Fashion-conscious patients should be encouraged to return with different make-up and favorite apparel before making a final frame selection. Patients whose wardrobes are mostly in the gray-blue tones usually look better with similar frame color tones or in silver metallic frames.

Shape
Square, rectangular, round, oval and triangular (base down or up) are the basic facial shapes. Usually, but not always, a lens shape that loosely mimics the facial shape is a good choice. Patients with oval facial shapes are fortunate in that they can potentially wear almost any basic frame shape. Those with facial shapes that are strongly square, rectangular, round or triangular usually do not look good in frames that too closely mimic their facial shape (e.g. round lenses on a round face can look “cartoonish”). On the other hand, round lenses on a rectangular or square face can often look out-of-place.

Patients commonly make the mistake of looking at their appearance in various frame styles from a too-close position to a mirror. It is easier to judge the appearance of a frame from a distance of 10 to 12 feet. Because of this patients should be encouraged to “step back from the mirror (refractive error permitting).” Assisting family members or friends can help best if they stay back and view the trying on of frames in the mirror but from several feet away.

Clinical Tip: The nasal edges of the eyewires should parallel the nose. If the angle of the bridge flares too much, the nose may look longer and narrower. If the angle of the bridge flares too little, the end of the nose may look more prominent. If the frame has a fixed bridge, too much bridge flare can cause pressure marks to appear high on the sides of the nose, while insufficient bridge flare can put pressure too low on the nose and interfere with breathing.

Size
Frame overall width should be about the same as the width of the patient’s face. The B measurement of lenses should generally be greater for long faces and shorter for round or square shaped faces. The patient’s PD should be equal to or 1 to 3mm less than the frame PD (i.e. the sum of the eyesize and bridge size). The width of the front should generally permit the temple to go straight back to the attachment of the external ear to the skull with the temples at approximately right angles to the front.

Design Nuggets
The following tips can help you achieve the best look and fit for your patient’s new eyewear.

1. Use turnback temples to make the overall width of the eyewear wider while keeping the lens size smaller.
2. Use a lens shape that allows the nasal side of the lens to parallel the nose.
3. For patients that would benefit by a wider appearing PD, use a frame with more decoration around the temple attachments and as plain a bridge arrangement as possible.
4. For patients with exceptionally wide PD and a relatively narrow face, use a frame with a more complex bridge and with temple attachments that are as simple as possible.
5. Use frames with fronts that are thicker (front-to-back) to disguise the thickness of higher minus lenses.
6. Use frames with fronts that have wide eyewires to minimize lens size (and thickness) for both higher plus and minus lenses.
7. Because a shorter vertex distance minimizes both facial inset and outset, consider using a frame with high temple attachments. This allows more of the lens to swing back toward the face when pantoscopic angle is added and reduces the magnification/minification phenomenon.
8. Patients who have deep-set eyes and “balcony brows” may benefit from using a frame with lower temple attachments because this allows the top of the frame to swing outward at the top. This may permit you to move the frame closer to the eyes for better optical performance and appearance.
9. Using a frame with the bridge attached higher will tend to make a too-short nose look longer.
10. Using a frame with the bridge attached lower will make a too-long nose look shorter.
11. Using a frame made from heavy stock works best for patients with large, coarser features.
12. Using a frame made from thinner stock usually words best for patients with delicate features.
13. Generally frames should follow the line of the eyebrows and should be at, or slightly below the level of the eyebrows.
14. It usually is not a good idea for the top part of the frame to cut across the brow, leaving some of the brow above the frame and some showing through the lenses.
15. Thicker, darker frames usually work best for patients with heavy eyebrows.
16. For most facial shapes the centers of the eyewires should fall at about the base of the pupils with the patient’s lines-of-sight straight ahead and level.
17. For long, rectangular faces, a deeper eyewire shape can give a good cosmetic appearance, but the MRPs may have to be raised well above the mounting line (i.e. half way from the bottom to the top of the lens) to be positioned appropriately.
18. A heavy or ornamented bridge will tend to make an unusually wide PD appear narrower and a simple, delicate bridge will tend to make a narrow PD look wider.

Design Analysis
Asking a patient what they liked and did not like about previous eyewear can help pin down what they find appealing in terms of eyewear appearance, as well as performance. Below is an example of how a careful analysis of lens and frame considerations can yield better eyewear appearance and performance.

In Figures 2 and 3, patient’s Rx is -4.75DS in both eyes. She has a rectangular facial shape, a relatively narrow PD and a long nose. Her upper lip is somewhat short and this makes the length of her chin from the lower lip downward to appear longer. In Figure 3, the eyewires are thin and delicate, which will make the thickness of the lateral edges more apparent. The temple attachments are very simple, which, coupled with a decorated bridge, would make her narrow PD even more evident. The high placement of the bridge accentuates her long nose. The lens shape is shallow (i.e. the B measurement is relatively short compared to the A measurement) and this further accentuates her long face, long nose and relatively short upper lip.

The frame simulation in Figure 3 uses a thicker eyewire to hide some of the lateral edge thickness and to prevent the brows from showing below the eyewire. The bridge is narrower and this, along with the reduced A measurement, means the frame PD will be closer to her anatomical PD, so less decentration will be needed and the lateral edge thickness will be reduced. The B measurement is increased and this makes her long facial shape less noticeable. The bridge position is lower to disguise her long nose. The bridge is simple and the DBL is narrower, these changes, coupled with some decoration at the temple attachments, helps give the appearance of a wider PD. Rolling and polishing her lenses will make the thickness of the lateral edge of her lenses less noticeable and make bulls-eye rings (not shown) of her myopia less prominent. Using both a light tint and AR lenses will further attenuate the bulls-eye rings. The MRPs are high and as a result the edge thickness at the bottom of the lens could be a problem. The roll and polish makes it less likely that her cheeks will touch the bottoms of her lenses when she smiles. The frames also have a low temple attachment, allowing the top to swing outward a bit and the bottom to swing inward less when pantoscopic tilt is added. Turnback temples could be used to keep the eyewear about as wide as her face while allowing a smaller eyesize to be used. Setting the vertical MRP position a bit lower than normal would help with the edge thickness at the bottom.

Prescription Considerations
The MRP is the point, and the only point in the lens that gives the exact prescription. As the patient’s line-of-sight roams away from the MRP, lens performance deteriorates. The area around the MRP, which does not interfere with clear, comfortable vision even with prolonged viewing can be thought of as the “sweet spot” of the lens.

The sweet spot tends to enlarge as adaptation to the  new lens occurs. This enlargement is limited by the lens design and by the patient’s tolerance. The sweet spot also varies according to visual demands, lighting and pupil size at any given time. The sweet spot tends to be smaller for stronger prescriptions, higher index materials and aspheric lenses. If the MRPs are placed somewhat lower to minimize the lower edge thickness for the frame on the right, then care must be taken to minimize anything in the lens design that could make the sweet spot smaller. If the new MRP placement is lower relative to the pupil than the MRP placement in the previous eyewear, the patient may feel somewhat taller in the new eyewear because of an increased base up prism effect when viewing straight ahead. Fortunately, this effect will pass within a day or so of wearing only the new Rx.

If the presciption was -4.75 -2.00 x 090, the design problems at the bottom (and top) of the eyewire would be much as described above because the power in the vertical meridian would still be -4.75. The lateral edge thickness would be greater however. If the axis of the cylinder was 180, then the power in the vertical meridian would be -6.75 and the design challenges would be greatly changed.

The correct choice of frames should leverage the advantages of today’s lens technology. Although ophthalmic technology offers many terrific options, if used inappropriately they can yield increased cost with little patient-perceptible improvement in appearance and disappointing results in visual comfort and performance. Reprinted with permission from Jobson Publishing.

L&T Expo Scouting Report
Spring 2009

03-2009


Edited by Andrew Karp

LENSES
At this month’s International Vision Expo East, attendees will be able to see the latest ophthalmic lenses and sunglass lenses. L&T’s eagle-eyed reporters have already scouted the market and bring you this special preview of what’s new and noteworthy in lenses.

In the ever-expanding progressive lens arena, Carl Zeiss Vision is debuting Zeiss Individual a progressive lens that is precisely personalized for the individual wearer. Zeiss Individual automatically expands or contracts the entire design for the size and shape of the patient’s chosen frame, balancing all viewing areas and ensuring the widest fields of vision. In addition, the patient’s monocular PD, vertex distance, pantoscopic angle and frame wrap angle are incorporated into the design calculation, resulting in maximum visual acuity for any face, according to Zeiss. Optimized optics for every prescription. Zeiss Individual creates and optimizes the design in “real time” based on the patient’s exact combination of sphere, cylinder, axis and add power, eliminating visual compromises.

Shamir Element, Shamir Insight’s elementary freeform, gives ECPs an opportunity to provide their patients with a personalized back-surfaced lens at an affordable price. The building blocks of the Shamir Element design are based on two essential technologies, EyePoint Technology and Direct Lens Technology, which together create a back-surface Freeform lens personalized to each patient’s unique measurements. Shamir Element shares several features with Shamir top-of-the-line Autograph lenses, including EyePoint Technology, Direct Lens Technology, back-surface design, Freeform manufacturing and wider fields of vision.

Indo International is showcasing its Free-form Solutions program, featuring progressive lens designs, a curve calculation program and professional assistance. Indo offers three options: Global Designs, which are multipurpose progressive lens designs and include Global 22, Global 19 and Global 16; Action Designs, a family of specialized progressive lens designs consisting of Office Design, Road Design and Outdoors Design; FreeDesign, a progressive lens design developed based exclusively on the characteristics and parameters provided by the client.

Essilor, celebrating the 50th anniversary of Varilux progressive lenses this year, will host the Varilux Experience booth, an experience in three dimensions. Open your senses to an interactive exhibition that demonstrates the history and future of Varilux lenses. Experience the progression of better vision. Essilor will also announce several product line extensions and new products during Expo.

Polarized lenses have never been hotter and several companies are launching new polarized lines this season. Essilor’s new Xperio polarized lenses feature industry-leading designs, materials and coatings to deliver superior visual performance and optimal comfort. In addition to UV protection, Xperio’s polarized lens technology virtually eliminates bothersome glare, allowing the wearer to experience the outdoor world more safely and more beautifully. Xperio polarized lenses come in all prescriptions and are available in a variety of colors.

Younger Optics is releasing NuPolar Trilogy, made of the ultra strong, thin and optically superior Trivex material. NuPolar was recently launched in 1.67 high-index (MR-10) and is also available in hard resin and polycarbonate.

See how polarized sunwear can be both functional and fashionable at an exclusive fashion show hosted by Specialty Lens for its iRx Polaroid brand. During the show, different characters walk down the catwalk, each with his or her own prescription and lifestyle needs. Specialty Lens will show how to cater to the individual lifestyles, activities and needs of patients. Showtimes are as follows: Friday, March 27, 4:30-5:30 p.m.; Saturday, March 28, 10-11 a.m.; Saturday, March 28, 1-2 p.m. For more information or to sign up to attend, please contact Carl Reese at Specialty Lens Corporation at (800) 366-1382.

On the photochromic lens front, Signet Armorlite will debut a new lens material for the InstaShades family of photochromic lenses. Participating in the large standard index photochromic lens market, the new 1.50 index lens will be an excellent choice for drill-mount and grooved frames. The lens will feature low density and high Abbe value, with excellent darkening and fading performance.

Shamir is expanding its single-vision product line with the addition of Polyplus Transitions Gray/Brown. The lens reduces glare and improves contrast for enhanced visual quality. PolyPlus material is lightweight, providing UV protection and the highest impact resistance. Approved coatings include Crizal, Hoya, iCoat and Zeiss.

Vision-Ease Lens is introducing the LifeRx 7x28 trifocal, which is available for shipment at the end of March. Like the LifeRx bifocal, the LifeRx 7x28 trifocal is designed for maximum durability. It is manufactured with 100 percent renewable energy to benefit both the wearer and the environment. The LifeRx 7x28 trifocal offers high-quality photochromic performance with rapid darkening, industry-leading fade-back speed and better indoor clarity.

Augen Optics premium high-definition, single-vision lenses are now available as NXT Sunlenses and NXT Varia Photochromic and Photochromic Polarized Sunlenses (activated by Transitions). NXT Sunlenses, offered through PPG, protect and improve vision with patented Trivex polymer that is lighter and stronger than polycarbonate, free of stress with superior optics and compatible with any type of frame. Augen NXT Sunlenses are available in a range of tint colors and in polarized, photochromic, polarized photochromic and mirror applications.

Stop by the Transitions Optical booth to learn about new programs and tools that ECPs can leverage to grow their business. Plus, find out about the new ways Transitions is reaching out to consumers about healthy sight, including new television commercials and designation as the Official Eyewear of the PGA Tour, Champions Tour and Nationwide Tour.

Seiko Optical Products will debut a new single-vision DiamondClear polycarbonate with Transitions lenses that includes factory applied Surpass AR. The company is also launching a 1.74 single-vision lens, which is factory AR-coated with SuperClean super hydro AR coating. The new lens is made with a new 1.74 index resin that’s exclusive to Seiko.

Pixel Optics is releasing a Transitions VI Gray and Brown option for its Composite 67 atLast! “Enhanced Multifocal” design, launched in November 2008. It combines a power gradient with an embedded power segment to provide four zones of clear vision—near, intermediate (18-inches to 29-inches away), far-intermediate (29-inches to five feet away) and distance. The atLast! lens provides continuous, wide vision from close-up to five feet away, with a soft power jump when transitioning from distance to far-intermediate. The soft power jump is 70 percent less than that of a bifocal of equivalent add power, according to Pixel Optics. Reprinted with permission from Jobson Publishing.

IN HIGH GEAR

01-2009

Zyloware adds the Stetson Off Road collection to its long-established Stetson eyewear brand. Targeted to men 20 to 40, younger and with a more youthful lifestyle than the traditional Stetson consumer, the new collection, as with all Stetson products, puts an emphasis on masculinity and quality with unobtrusive, but modern styling. Included are five metals and one zyl, all with spring hinges. The metal frames are equipped with snap-in, silicone nosepads. Shapes are variations on rectangles. Two designs are semi-rimless. Colors range from black, gun and tortoise to tan, bronze and gold with antique finishes.

PHILOSOPHY: “The Stetson brand has been a bestseller for Zyloware for 27 years. It’s a firmly established iconic American brand that carries with it expectations of masculine styling, comfort and wearability ingrained with the American spirit of individuality—hence the tagline ‘Made of America,’ says Christopher Shyer, Zyloware president. “The new collection has all these attributes with a younger feeling—reflecting the Stetson company’s new marketing approach—using such celebrities as actor Matthew McConaughey and football star Tom Brady to create a sexier, more youthful appeal.”

MARKETING: Merchandising materials include a six-place counter display with interchangeable header cards and double-sided tent card with imagery that speaks to where the consumer aspires to be. An emergency roadside kit is free with the purchase of any six Stetson Off Road frames and includes jumper cables, voltage tester, knife with retractable blade, electric tape, drive screwdriver, drive coupler eight, metric socket and two each of hex head drives, torx head drives, flat head drives and Phillips head drives.

PRICE POINT: $$. For additional information, contact Zyloware, (800) 765-3700; web site: www.zyloware.com

TIP
Stetson Off Road styles are priced so they can fit into many managed-care plans. Reprinted with permission from Jobson Publishing.

X-TRA SPECIAL

01-2009

Sàfilo USA adds the Chesterfield XL ophthalmic collection to its Chesterfield eyewear line. Targeted to the larger man, the XL styles are geared toward men 25 and older and—just like all Chesterfield products­—feature affordable all-American styling that suits an active lifestyle. Included are four metal frames, each incorporating larger eye and bridge sizes and longer temples. Delivering both modern and classic appeal, the designs consist of rectangular shapes (one style is semi-rimless) and a double-bridge aviator. Colors include brown, opaque brown, ruthenium and dark ruthenium with a semi-matte finish.

 

PHILOSOPHY: “As a leader in the eyewear industry, it is imperative to recognize the needs of our customers, which is why we are very excited to be introducing the Chesterfield XL collection,” says Dick Russo, Sàfilo USA executive vice president. “This collection, designed for a specific niche in the market, will offer our larger male customers a better fit and added comfort in their eyewear.”

MARKETING: An XL logo has been designed for the collection.

PRICE POINT:  $$. For additional information, contact Sàfilo USA, (800) 631-1188, www.safilousa.com

TIP
Extended endpieces provide extra width, giving individuals with larger faces the option of wearing smaller eye shapes. Reprinted with permission from Jobson Publishing.

EYE ART

02-2009

 Lafont presents Riviera, its Spring/Summer 2009 collection, consisting of 35 ophthalmic and sun styles in 170 skus for men and women. Chic and sophisticated, the new line is constructed from such materials as acetate, titanium, beta titanium, milled metal, stainless steel, aluminum and wood often in combination. Openwork and such accents as rhinestones, coral, resin insets and studs appear throughout the collection as do lacy and tweed-like textile effects. Approximately 40 new colors were created exclusively for Riviera. Also part of the new line, the Riviera Coffret is a limited-edition wooden box collection containing two styles: Baroque, a trapezoid design ophthalmic frame combining an acetate front and stainless-steel temples with coral openwork, resin inserts and Swarovski crystals; and Bermudes, an acetate sunglass with acetate imbedded coral motifs and a Swarovski pearl. Both styles are offered in a variety of colors including Riviera (orange coral on black), created exclusively for the collection.

  

PHILOSOPHY: “Inspired by the timeless charm of the ’30s and the relaxed elegance of summer on the Cote d’Azur, the Riviera collection reflects a very French life-style—chic and luxurious,” says Lafont.

MARKETING:  Countercards and banners in varying sizes are available.

PRICE POINT: $$$ to $$$$$. For additional information, contact Lafont, (800) 832-8233; web site: www.lafont.com

TIP
The Riviera Coffret limited edition set is targeted to the Lafont female consumer who wants something exclusive and special from Lafont. A proprietary color, Riviera, was created for the set so the wearer can coordinate her ophthalmic frame and sunglass to complement her wardrobe. These two styles also have serial numbers to indicate limited production. Reprinted with permission from Jobson Publishing.

 

THE DOGS TAKE TO THE RED CARPET 03-2009 In collaboration with celebrity stylist Phillip Block, Kenmark Group launches a guest designer series of eyewear: Phillip Bloch for Hush Puppies. Included are 10 metal, zyl and combination frames in a masculine color palette. These fashion-forward styles offer classic shapes with a modern twist on vintage eyewear, providing an all-American look inspired by themes such as turn-of-the-century industrial age, art deco and vintage 1940s and 1950s geek chic. Several frames feature twin-flex technology—an exclusive dual spring hinge system with two flex points on the temples for maximum comfort and fit.   PHILOSOPHY: “As a celebrity stylist and designer, I’m constantly visually stimulated and have realized the importance of vision,” says Phillip Bloch. “I was inspired to create a line of glasses that have my ‘fav’ four aspects of style: sexy, comfortable, affordable and transformational—officious for the office, cool for play and chic for evening. So no matter where you are in your day everyone will be looking at you while you‘re seeing the world through eyewear with star style by Phillip Bloch.” David Duralde, Kenmark vice president for creative development, adds: “Phillip Bloch’s great taste and flair for dressing celebrities adds a new dimension to Kenmark’s design direction.” MARKETING: Each frame comes with a soft case with a pocket that can be used for credit cards and other personal items. PRICEPOINT:   $$. For additional information, contact Kenmark Group (800) 627-2898; web site: www.kenmarkoptical.com TIP Founded in 1958, Hush Puppies is widely credited with creating America’s first casual shoe, signaling the start of today’s relaxed style. Since the beginning, the lovable basset hound mascot has become synonymous with the brand, which is now sold in more than 140 countries. Reprinted with permission from Jobson Publishing.

 

03-2009 Ray-Ban, from Luxottica Group, presents the Ray-Ban Caravan reinterpreted in an exclusive limited edition featuring precious materials combined with sophisticated technology. Created in 1957, the Ray-Ban Caravan with its characteristic square lens shape immediately established itself within the American, and later global market, securing its place as an alternative to the aviator drop shape. These now legendary glasses introduced lightness and minimalist design to the Ray-Ban portfolio. The new frame features a titanium front and beta titanium temples and is entirely covered in 18-carat white or yellow gold, a precious material with resistance to moisture and oxidation. The frame is equipped with gold or silver-colored mirrored P3 Plus lenses made of high-quality glass with a polarizing filter guaranteeing superior, high-color definition. The lenses also feature AR and water-repellant treatments. Only 20,000 pieces of the Ray-Ban Caravan are manufactured worldwide, each numbered on the inside temple.   PHILOSOPHY: “The Ray-Ban brand is synonymous with quality and functional excellence and the new Ultra Gold Caravan Limited Edition perfectly showcases this excellence,” says Vittorio Verdun, vice president of marketing, Luxottica Group. “With premium frame materials and lenses exclusiveto this style, the Ultra Gold Caravan Limited Edition frames assure top-class performance and exclusivity—all in a classic and iconic style.” MARKETING: Merchandising materials include a pedestal display, dispensing tray and logo plaque. Each sunglass comes packaged in a box with a leather case and information brochure. PRICEPOINT:   $$$$$. For additional information, contact Luxottica Group, (800) 422-2020; web site: www.luxottica.com TIP Ray-Ban Ultra Caravan Limited Edition arrives one year after the extraordinary success of the first limited edition Ray-Ban Ultra collection celebrating the iconic aviator style. Reprinted with permission from Jobson Publishing.

MODERN VINTAGE

03-2009

Sàfilo USA celebrates its 10-year anniversary with the Fossil brand by adding a women’s line to the popular collection. The four ophthalmics are geared toward youthful, modern women seeking reasonably priced, stylish products. One metal, one plastic and two metal/plastic combinations are available in softened rectangular and oval shapes; one frame is semi-rimless. Designs and colors are inspired by Fossil accessories, especially the women’s watch collection. Colors include black, brown, plum and rose with satin finishes and combinations of satin black/moss, satin sand/cream, plum/deep plum, black/tortoise, deep plum/red and brown/tan cream.

 

PHILOSOPHY: “We've had a very successful partnership with Fossil for the past decade and are very excited to add women’s styles to commemorate this important milestone,” says Dick Russo, executive vice president of Sàfilo USA. “Fossil is a powerful and trusted brand name that resonates strongly with both men and women. The attractive price point and exceptional styling in the women’s Fossil collection should help the line do very well in the marketplace.”

MARKETING: The marketing program will include promotions and such visual merchandising materials as a one-place highlighter, six-place rotator, posters, countercards and logo plaque.

PRICEPOINT:   $$. For additional information, contact Sàfilo USA, (800) 631-1188; web site: www.safilousa.com


TIP
Founded in 1984, the Fossil brand was originally known for stylish watches at affordable prices. In the 1990s, the company expanded into accessories, including handbags, wallets, belts and small leather goods. Fossil products are sold in more than 90 countries worldwide. Reprinted with permission from Jobson Publishing.