L&T: Lens Choices

Oct
2005

Lens Choices


As with everything, today’s kids want what adults want. Fortunately, the popular lens trends that are dominating the adult market also offer excellent benefits to children. Until recently, the key issue for evaluating lenses for both children and adults was performance. However, when prescribing or dispensing lenses for children, fashion and safety are also important considerations. Taking those three factors into account, the leading criteria for lens selection are materials, designs and upgrades.

Materials
Peer acceptance is very critical for most children, so any lens that is thinner and less obtrusive will help the child feel more like one of the crowd. The higher-index materials and polycarbonate in particular make for better cosmetics through thinner profiles while their lighter weight allows for greater wearing comfort. (One less excuse for a child to not wear their glasses.) The improved impact resistance of polycarbonate and Trivex permits greater freedom to select almost any frame as it allows a maximum level of safety. These more durable materials make even rimless mountings, which make up about 25 percent of all frame options, a stylish and practical choice for young people. Even in lenses that are thinner at the center, polycarbonate offers 10 times the impact resistance of ordinary plastic and 25 times the impact resistance of glass lenses. This is extremely important, because virtually all children, whether or not they lead active lifestyles, encounter everyday incidents that can generate potentially hazardous impacts.

A 1997 study reported in the Journal of the American Medical Association found that of all common lens materials, polycarbonate was the only one that did not break when struck with the level of force generated by accidents such as falling off a bicycle or getting struck with an inflating automobile air bag. Since that study, new materials such as PPG’s Trivex have been introduced with the promise of safety on a par with polycarbonate. In fact, the “Duty to Warn,” an Optical Laboratories Association program based on the legal principle of “informed choice,” requires responsible dispensers to tell patients about the relative impact resistance of lens materials so they can make informed decisions about safety. Because liability is a major issue, practitioners would be wise to direct youngsters and their parents to the newer high-impact resistant lens materials where performance and safety meet to form a complete package.

Another area where these new generation materials benefit young people is ultraviolet protection. The threat to eye health posed by ultraviolet light is usually not seen with the same urgency as that of an impact injury, but the long-term damage caused by a lifetime of unnecessary exposure is of no small concern. While plastic lenses only block 50 percent of the ultraviolet, all the new materials, including polycarbonate and Trivex, offer maximum UV protection. Since the protection is inherent in the material it makes good sense to choose the lens that offers a lifetime investment in healthy vision.
The final thought on lens materials concerns cost. Parents often hesitate to purchase the slightly more expensive new materials in favor of plastic for fear that replacement costs would be too expensive. Fortunately, most polycarbonate and Trivex lenses are offered with high-performance scratch coatings and many come with a replacement warranty.

When it comes to choosing a lens material polycarbonate and Trivex provide performance, protection from impact, ultraviolet light and scratching as well as a great measure of versatility.

 

L&T basics
framing youngsters for the fit of their lives
The greatest concern of fitting children with glasses has often been overcoming their fear of being different. Frame options for children were merely miniature versions of adult frames in a wild splash of non-adult colors.
However, young people currently are maturing at an accelerated rate. Childhood has been shortened by the emergence of the tween years as a separate stage of development. In response, frame vendors have modernized their product lines to better reflect kids, tweens and teens attitudes. Eyewear has become an accepted, even desirable fashion accessory. Selecting a child’s frame today will revolve on the issues of style acceptance (“Is it cool enough to wear around my friends?”) and technical considerations of fit (“Will it work on a smaller face?”).
Keep these points in mind when choosing frames for young people:
• While there are many tricks and techniques that may be used to adapt frames to the patient’s particular needs, it makes good sense to start off with a frame choice that is as close to factory-ready to fit as possible.
• A frame used by a youngster should have strength and flexibility. An inexpensive frame that will need constant repair and replacement will cost much more over the long run than the very best frame designed to hold up under rough treatment.
• A more technical issue is matching the width of the frame to the child’s face. The frame front should be wide enough to allow for a generally straight path from the end piece to the ear. Contrary to what parents may think, purchasing oversized frames with the intention that the child will grow into them is not advisable; large frames will be uncomfortable and likely unwearable.
• Selecting a frame with a good nasal fit should be of critical concern because the bridge of the nose supports 90 percent of the eyewear weight. Bridge fits, which distribute the weight of the glasses over a larger area of the nasal surface, create less pressure and therefore convey more comfort.


Lens Designs
In the area of lens design two excellent options for children are aspheric lenses and short-corridor progressive lenses.
For pediatric patients, aspheric lenses can have a significant psychological and optical advantage. Children are very sensitive to how their lenses look, especially hyperopes whose lenses are often bulgy and thick. Aspherics make for flatter, thinner more normal looking lenses by reducing magnification in plus prescriptions and minification in minus prescriptions. Other kids don’t make fun of them, they feel better about themselves and they have better compliance in terms of wearing their glasses, which serves to aid treatment of their problem. These new lens designs can satisfy a youthful audience driven by the need to always look their best.

Some doctors prescribe standard bifocals for therapeutic reasons, but usually the best choice is the lesser obtrusive option, progressive lenses. Many eyecare professionals recommend progressives for children, especially those who have an accommodative problem like excessive convergence, where the eye wants to over-turn, over-shoot and over-focus. Many doctors recommend progressives lenses for children who are in the third and fourth grades and are at a peak period of visual activity. They are faced with an increased amount of material to read, are expected to read smaller point size and work longer at the computer. The near-variable focus lens, which has a wider corridor, lets them focus at the computer without their vision becoming blurry when they look further away.

Many practitioners recommend a progressive lens to give children clear distance vision as well as the extra power needed for close work to relax their vision and avoid premature myopia. ECPs who prescribe progressive lenses to children say that children adapt easily to the lenses because they provide more natural, functional vision throughout the day compared to flat-top 28 bifocals. They say progressive lenses increase compliance, are cost effective and provide excellent correction for accommodative esotropia and myopia control.
In the past progressives were designed for adults who wore larger frames. With minimum fitting heights from 18mm to 21mm progressive performance was often cut short for youngsters whose frames had B dimensions of 35mm or less. To keep pace with smaller frame styles (many frames now have a B dimension of 35mm or less) lens suppliers have developed short-corridor progressive lenses. Short-corridor progressives, some of which can be fitted as low as 14mm, makes it possible for youngsters to reap the full advantage of progressive design. Progressive lenses give the youngster the fullest range of vision (distance, intermediate and near) and help them avoid the stigma of bifocal lines. Whether doing homework at the computer or just playing video games the variable focus of progressives offers youngsters the great advantage of natural vision. Typically, wearing times and care of eyewear improve when the child likes what they have on and are comfortably visually and appearance-wise with it; instances of loss and damage to the frame and lenses decrease.

Upgrades
The third criteria for lens selection are upgrades or enhancements, often referred to as “add-ons.” However, add-ons is a negative and inaccurate term that fails to correctly represent a true enhancement as it implies a last minute “throw-in” meant to pump up the sale rather than benefit the wearer. In the case of eyewear this label often used for lens enhancements doesn’t represent the true picture. Enhancements such as photochromic and anti-reflective are integrated into the lens and remain with the product for its entire life. The nature of a true upgrade or enhancement is that it connects directly to performance, style and safety, the original criteria for selecting any lens.

The new generation of anti-reflective (AR) lenses has overcome past problems of failure due to scratching, cracking and difficult cleaning. The purpose of corrective lenses is to deliver clear natural vision in real world situations. An eye exam done in a darkened room with a lighted screen artificially creates the ideal situation for finding the best acuity in a high contrast environment. The problem, as most dispensers will agree, is lens wearers often complain they see better during their eye exam than with the actual lenses. This is usually because the exam environment provides ideal contrast while the real world, a blend of all lighting conditions, does not. In order to compensate for an uncontrolled environment photochromic and AR lenses help by selectively providing useful light as they eliminate problem light.

AR lenses are less visible on the face, again addressing the youngsters’ psychological need to fit in. Better vision will result since AR enhances contrast sensitivity by eliminating distracting reflections from overhead classroom lighting as it takes the edge off computer screen glare. In a similar vein, photochromic lenses will adjust to a variety of lighting conditions to automatically and instantaneously create the best visual environment.

Kid vs. Parent: Both Sides Can Win
Of course the age-old difference of opinion between young people and their parents applies to the choice of eyewear. The optical industry has worked hard to eliminate those conflicts by making today’s technology-driven frame and lens choices durable, attractive and comfortable. The priorities in children’s eyewear should always be good vision, comfort, looks, safety and value.

Today’s youngsters can choose from stylish frames that mirror the latest adult fashion trends. Lens design choices cover the spectrum of a young person’s needs, from lightweight thinness to eye protection during sports activities.

Options such as anti-reflection and photochromic lenses offer fashion with function for all ages. As to value—an area where parents and youngsters often don’t see eye-to-eye—the best eyewear may cost more, but with warranties and the durable quality of today’s frame and lens materials, investing in the best usually translates into a savvy consumer choice. “Pay me now or pay me later” certainly applies to children’s eyewear. The best options will definitely balance out to a happy parent, happy child and outstanding value for everyone. LT

 

|