Need Based Solutions - Lenses
08-2008
Progressives for Presbyopia
 Understanding progressives makes explaining their advantages easier. If you are presbyopic yourself and wear progressives, it’s really easy. If not – here’s what you need to know. The front surface of a progressive lens steepens towards the bottom and that creates a gradual increase in plus power (Fig. 1). The result is a smooth, continuous increase of the add power, without visible lines or interruption of vision.
There are three distinct zones of vision. Distance, a stabilized zone located in the upper portion of the lens, provides the far vision prescription. The Near, is a the lower add portion of the lens, and the Intermediate, a central ‘corridor’ that connects distance and near increasing progressively in plus power (Fig. 2). These three zones of vision blend together seamlessly, providing the wearer with a continuous range of vision from distance to near.
Modern progressives have minimal blur i.e., the astigmatism created has been reduced to the mathematical limit or about equal to the add power. New digital surfacing techniques in lenses like Varilux Physio 360º and Definity allow the astigmatic and other errors to be further reduced so there is little blur. Patients will comment that the lenses are clearer overall and with crisper, higher contrast images. This is accomplished by increasing the precision by which the molds are cut to make a semi-finished progressive and then further reducing the remaining errors by compensating for them on the back surface of the lens. The result is progressive lenses with eye comfort, smooth transitions throughout the lens, amazingly clear vision and the most natural-like vision.
The newest designs are adjusted to the wearer’s prescription, frame choice, physical measurements and visual habits. They include variable inset and corridor lengths, corridors have been shortened, and the designs are changed considering the prescription’s magnification and minification effects.
Varilux Physio and Physio 360 have allowed us to upgrade many of our patients to a superior lens design. The lens is available in a large range of materials and options, which is very beneficial, no compromise is made by making it necessary to select a lens around patient needs/wants. The overall lens clarity and reduced “peripheral blur” set a new standard for progressive lenses.
Jeff Rohlf, LDO
Eyewear Gallery Supervisor
Optical Lab Instructor
College of Optometry, Ohio State University
Lens Clarity — Anti-Reflective Lenses
When it comes to providing the clearest vision to your patients, anti-reflective (AR) lenses are critical to providing your patients with optimal vision.
Recommend AR lenses to all your patients because it is best for all patients. Its performance has been shown to provide the most patient satisfaction and, as a result, the least issues for the optician.
Surface reflections are also increased as index increases. As a result, it is important that all lenses, especially high index lenses, include anti-reflective treatment. This is why the Essilor Thin&Lite 1.74 lenses are always delivered with an integrated AR. How is the best AR constructed and how does it work?
High performance AR (Fig. 3) is composed of a combination of the following:
• Bare front and back lens surfaces
• Special hard coat applied directly to the lens surface (1)
• High energy bombardment etches and activates the surfaces (2)
• Application of the anti-static layer
• Application of a specialized AR stack of low and high index materials (3)
• Application of the super hydrophobic, oleophobic treatment (4)
• Essilor patented Pad Control Layer is required to allow for edging
• Systematic QC inspection.
All of this results in more transmission, highly durable, easy-to-clean and stays cleaner longer lens for your patients/consumers.
AR lenses improve visual acuity, and the overall aesthetics of glasses. They allow more light to reach the eye, providing better vision and reduced reflections, so patients see better and others see their eyes more clearly. Good AR treatments eliminate glare from overhead lights, computer screens, TVs and headlights. This means that glare that would normally cause eyestrain and fatigue, or make night driving more difficult, is virtually eliminated.
Lesser performing AR does not apply the same scratch resistance to the back of lenses. Since 40 percent of all scratches occur on the back lens surface, double side hard coating of the same quality is important. Then, surfaces are protected by Essilor’s patented Pad Control System, which allows easy blocking and lens edging even with the highly slippery hydrophobic surface.
The Crizal Avancé with Scotchgard Protector Lenses addresses every former complaint with AR treated lenses. This AR technology is bonded to the matrix of the lens, more scratch resistant than an untreated lens and never “peels off or crazes”…in fact I tell them it’s guaranteed! Keeping this lens clean is a snap, with Scotchgard; in fact it is so “slippery” that it is actually easier to keep clean than an untreated lens. Finally AR lens treatment allows at least 8 percent or more light to reach your eye, helping with night driving and eliminating annoying reflections, all while enhancing the appearance of your glasses! To quote a colleague, Peter Shaw-McGinn, OD… “Would you like your lenses…with or without glare?“
James D. Colgain, OD
Lieutenant Colonel, USAF Retired
OD/MD Group Practice
Washington DC and Maryland
Variable Tint —
Photochromic Lenses
Photochromic eyewear is convenient, comfortable, protective and fun. Photochromic lenses include dyes made of molecules that when activated by ultraviolet light (UV), change shape and appear as a color tint. As more molecules change, the darker the lens becomes. Available in all the most popular indices and lens designs, every patient can enjoy the convenience of variable tint lenses.
Activation – In the unactivated state (no UV) the dye molecules remain colorless. The lenses automatically change in sunlight when invisible UV radiation hits the lens surface. Remove UV and the lens becomes colorless. At higher altitude where UV is less filtered, photochromics can get very dark. At sunrise and at dusk, as the sun gets closer to the horizon, UV is filtered through more of the atmosphere and may not be as dark as they are during the brightest times of the day.
To a lesser extent, modern photochromic lenses are somewhat temperature sensitive. In very hot weather, lenses do not get as dark as they do at milder temperatures. However, this is rarely a problem for wearers today.
Speed – In one minute, gray Transitions VI lenses get sunlens dark, 82 percent dark, 18 percent transmission (73ºF) and clear fast: 9 minutes to 70 percent transmission. For comparison, after a minute, brown lenses are 78 percent dark, 22 percent transmission and clear to 70 percent transmission in seven minutes.
Comfortable, Convenient and Protective – Photochromics react automatically and absorb 100 percent of UVA and UVB radiation, linked to cataracts, skin cancers and other ocular conditions. Variable tint lenses ensure that patients are comfortable in any light, minimizing eyestrain and eye fatigue. They minimize discomforting and disabling glare, add AR, and they minimize distracting glare, both night and day.
Tell patients that they can wear photochromics as clear lenses, all day, every day. In fact they work just like clear lenses in all
situations like driving, at the computer and for movies and TV. Congratulate them on their sophisticated choice of lenses.
No Glare — Tints and Polarized Lenses
Glare knows no season so recommend glare protective eyewear to all patients all year round. In this case, sun lenses protect the patient from discomforting, disabling and blinding glare. Medium to dark tints address the first two while polarized lenses can do all three and eliminate blinding glare.
Light and gradient tints can add to the fashion of glasses, just look at the variety of large plano sunwear seen in every Sunday fashion supplement and magazine. The variety of colors and depth of gradients add to an exciting overall look. Use polarized lenses for the most protective and comfortable vision in sunwear. A polarized lens virtually eliminates glare by absorbing sunlight reflecting off water, glass, snow or sand.
Light is horizontally reflected off flat surfaces. Crystals in polarized lenses are arranged to create a vertical polarizing filter that lets only the useful light through. Polarized lenses improve contrast and enhance the visibility of all colors. Available in 1.67 high index, polycarbonate, Trivex and plastic, polarization can deliver the right thinness, lightness and properties personalized for each wearer. Polarized lenses provide 100 percent protection from harmful UVA and UVB rays.
Polarizing Pearls – Verify the axis of a polarizing Rx lens by using a plano polarized lens held with its polarizing axis vertical (at 90 degrees). If the Rx lens’ polarizing axis is correct (at 180 degrees), the two polarizers when crossed at 90 degrees will be black.
Eye Protection —
Radiation and Sunlight
UV radiation is divided into three types, or bands - UVA, UVB and UVC. The ozone layer above the earth absorbs UVC, (200-290nm), but not UVA and B radiation. The UVA and UVB that reaches the Earth's surface contribute to serious health effects. UVB (315-290nm) can be characterized as burning, UVA (380-315nm) are aging rays. UVA causes wrinkling and mottling of the skin, and damages the collagen layer. Both UVA and UVB are known causative agents for cataracts, skin cancers i.e., basal, squamous and melanoma cancer.
 At birth, the lens of the human eye is almost 95 percent transparent and remains quite clear for the first decade of life. As the crystalline lens gradually loses transparency and begins to yellow, the amount of UV penetrating the lens decreases. By age 25, less than 20 percent of UV rays reach the retina. So start with sunglasses young.
Transitions reports that 80 percent of consumers are aware of the skin dangers of sunlight, only 10 percent are aware of the eye dangers.
There is some general agreement among researchers and experts that blue light is the most damaging wavelength to the retina, and most likely to contribute to the development of Age Related Macular Degeneration (AMD). Blue light penetrates to the retina; UV typically does not.
All this means that all lenses should be 100 percent UV absorptive. Using materials like high index, polycarbonate or Trivex and treatments like photochromics and/or polarized ensure that the lenses dispensed are most UV protective for patients. Absorbing blue light requires sun lenses with specific HEV filtering abilities. It also means that all children should be wearing sunglasses to protect the development of their eyes. It is estimated that almost 80 percent of the damage from UV is done by the age of 18.
What Would You Do?
PATIENT SITUATION
Mr. Diamond, a warehouse supervisor, is in to get his glasses adjusted. He has been wearing flat top 28 bifocals for about 14 years but doesn’t appear completely happy
with them since his last prescription change (about 4 months ago). He describes the “gymnastics” he does to see everything on his desk and his desktop computer screen clearly when he is in the office. Most of the time he is walking through the warehouse referring to a clipboard and PDA. Distance and near vision appear to be
fine – “It’s everything in between that’s the problem”, he says. With a distance Rx of about +1.00 and an add power of +2.25 what might you do?
SOLUTION
Mr. Diamond now wears his glasses all the time, his bifocals provide good distance and near vision, but his loss of accommodation no longer provides clear mid-range vision. The solutions are simple but require a little explanation. First, a progressive lens would provide immediate advantages; the blur of the segment for walking around would disappear and be replaced by clear mid-range and continuous vision from side to side as well as distance to near.
This is a good general purpose solution adding AR and the convenience of Transitions for the times that he is outside at the loading dock. However, if that desk work is more than 2 hours a day, a logical other pair of glasses can be a pair of computer lenses or to meet his budget, a pair of FT28 intermediate/near bifocals would work well when he is at his desk. AR is another must here since it reduces the glare form the screen and adds to comfort.
Eye Protection – Impact Resistance
In 1971, the Food and Drug Administration (FDA) implemented the requirement for the minimum impact resistance of all lenses sold for eyewear. Issued in the Federal Register, FDA21CFR801.410 became the standard that requires that all lenses must be shown to withstand the force of a 5/8 inch steel ball dropped 50 inches. This is called the drop ball test.
Since 1971, there have been many changes to the designs, materials and coatings of lenses but the standard remains, all lenses must be able to pass the “drop ball test.” As a result, any manufacturer or laboratory must have testing programs in place to show compliance.
Material, lens thickness and coatings affect the final impact resistance of the lens. Again, manufacturers, laboratories and lens distributors must be in compliance with the law. For more information on your responsibility for the impact requirements, contact The Vision Council (www.visionsite.org).
Hard coats like Essilor TD2 and the Crizal AR family use an impact enhancing primer as a first layer when coating lenses. This assures that Essilor lenses have enhanced impact resistance. More than the inherent impact strength of the materials
themselves.
Our Practice's Vision Statement is "Preserving and Protecting Vision for Life." Macular Degeneration is a leading cause of blindness and one of the controllable risk factors is sun/UV exposure. More people are exposed to sun with their lifestyles. That, coupled with the depletion of the Ozone Layer is allowing more UV to penetrate our eyes and skin, two organs that can be damaged by the sun. We don't "sell sunglasses," we offer protection against the risks of Macular Degeneration and other damaging affects from the sun. If a patient does not choose a separate pair of sunglasses we move to Transitions, clips, fitovers. Our goal is to protect our patient's precious vision. It makes what we do feel so much more worthwhile than just getting the sale.
Carole Miller, Optical Lead
Optometric Eye Care Center
Fridley, Minnesota
IMPROVE SUNGLASSES BY ADDING AR
Improve any sunlens by adding AR to the lens back surface. It improves visual acuity by reducing back surface reflections and improving contrast. It also enhances a lens’ high performance filtering ability. Dark lenses increase the visibility of normal
surface reflections and the back concave shape magnifies the size of the reflection. This can be annoying or obscure vision at the most important time.
Add AR to the back surface and it does the following: makes back surface reflections virtually disappear, improves scratch resistance of many materials, adds a hydrophobic that makes cleaning easier and improves acuity for the most effective vision outdoors.
Adding AR to polarized lenses is straightforward; it does not change the color of the polarizing lens. However, when adding AR to tints, the cleaning process may leach tint and change the color of the final lens. This results in problems. Instead consider Crizal Sun for all sunwear, tints and polarized. Crizal Sun is unique in that it maintains the desired tint color and intensity that is shown to patients. This is a major advancement in sunwear.
Crizal Sun has the superior scratch resistance and cleanability of Crizal Alizé because its hard coat is applied to both sides of the lens. The Crizal Alizé AR layer is then added to the back side of the lens to virtually eliminate back side glare and reflections. For tinted sun lenses, Essilor uses a patented slow-dye technique to allow the dye to penetrate the substrate more deeply, ensuring lasting color and intensity. Crizal Sun is integrated into the lens. An ion gun is fired at the substrate. This ionization process creates a more porous or rougher surface, allowing for better adhesion between the substrate and coating. Crizal Sun will not wear, peel or craze, giving patients the durability they need from their sunwear.
The lens material provides UV protection. It will not absorb any of the activating UV that make photochromics work.
Computers Are Here to Stay
It’s no stretch to say that 95 percent of your patients use a computer or other electronic devices every day – and many spend well over half their waking hours looking at intermediate or near distances. Why aren’t 95 percent of your patients wearing lenses prescribed for these activities? In most cases, it is because they aren’t aware of their options or the benefits of well-dispensed intermediate lenses. Don’t general-purpose progressives provide intermediate vision? Yes, they do, but not with the width that is needed for all day comfort at the computer.
Remember the corridor narrows as add power increases and in a small frame, short corridor lens, the vertical availability of each power is also reduced. So, the intermediate is okay for non-critical tasks, but for two hours or more per day at the computer, computer lenses work best. How can you solve your patients’ intermediate vision problems? The steps are as simple as Ask, Test and Dispense.
Ask - Make sure every patient gets asked about their computer use and other intermediate activities. “How many hours each day do you use a computer, PDA, cell phone, or other electronic device?” Have the receptionist mark their chart, so the doctor and/or optician is alerted that this patient needs to be educated on intermediate lenses.
Test - Test every patient at intermediate and write a second Rx for intermediate lenses. This simple step communicates to the patient just how important it is for them, given the visual demands of their daily life. Many doctors use the PRIO Vision Tester, which duplicates the focusing demand of a computer screen in the exam chair. This test is quick, accurate, and very convincing to the patient.
Dispense - For non-presbyopes, a typical lens solution is a second pair of single vision glasses with a near/intermediate Rx to be worn at the computer or while doing other close-up work. For presbyopes, it means a second pair of task-specific glasses utilizing a near variable focus lens, with an enlarged central, intermediate vision zone. Get a pair of these lenses for yourself, and be fully versed at describing their benefits.
Here’s how they work. Computer lenses are reading lenses that lose plus power (range or degression), as the wearer raises their eyes. For example, to see clearly at twice the reading distance, the patient would need half their add. Therefore, choose the computer lens range by knowing how far away the monitor is or other important materials. The higher the add power and/or the farther away clear vision is required, the higher the range is needed.
Computer lenses allow patients to be physically comfortable working at their desk all day. The greatest benefit is a lack of neck or back pain to the patient. Just drop the idea to the patient — allow them to assess their work environment and they will return requesting something to help them.
Mary Schmidt
President, EyeSystems
Walnut Creek, CA
What Would You Do?
PATIENT SITUATION
“Help, the computer screen is not clear and I do have
special computer glasses,” says Mr. Bonatello. When his
patient record is retrieved, you see that the lenses were
dispensed 4 years ago. There were other changes also; the
monitor became a flat screen, previously 18 inches away,
now 28 inches. However, the flat screen is still at eye level
on the shelf of his workstation.
SOLUTION
Three things, at least are happening. First, odds are that
Mr. Bonatello needs a new Rx since its been 4 years. With
an add change the range of the current lenses is not tuned
for the distances he needs. Next, the screen is further away
so less add power is needed for that distance. Last, the
screen is too high and requires that he raise his chin to see
clearly. So…
Make an appointment for an eye exam. With the results,
he’ll need a power range that sees clearly out to at least 28
inches but farther is better so that it includes more of the
desk and its surroundings. Rule of thumb: Half the add
power is needed to see twice the reading distance so if
reading requires a +2.00 add at 16 inches, then to see
clearly at 32 inches, a +1.00 add is required. A range of at
least 1.00D would give more utility.
Lastly, place the screen on the desk surface so that he is
viewing the screen downward. This position is more natural
and would be more comfortable.
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