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All lens materials block some light from passing through the lens. This light reflects back from the lens surface, causing distractions and reducing the clarity of night vision. Conventional glass or plastic lenses reflect about 8 percent of the light that otherwise would reach the eye. High-index lenses reflect up to 50 percent more light than conventional glass or plastic lenses. However, when an anti-reflective lens coating (AR coating) is applied, high-index lenses transmit 99.5 percent of the light. And by allowing more light to enter the eye, AR coatings provide sharper night vision with less glare — a real advantage for night drivers. AR coatings also eliminate lens reflections, they make high-index lenses appear even thinner. This is a big plus if you want to improve your appearance in eyeglasses.
Anti-reflective coating (also called AR coating or anti-glare coating) improves both your vision through your lenses and the appearance of your glasses.AR coatings are similar to the coatings found on microscopes and camera lenses. They consist of several layers of metal oxides applied to the front and back lens surfaces. Because of the layering effect, AR coatings sometimes have a hint of green or purple color, depending on the individual manufacturer’s formula.Each layer is scientifically calculated to block reflected light. The result is that you’ll see a reduction in glare, annoying reflections and halos around lights. This is a great safety benefit when you’re driving at night.Anti-reflective coating reduces the glare that you see, as well as the glare that others can see on your lenses. An anti-scratch coating can lengthen the life of your lenses, while hydrophobic coatings keep rain, snow and fog at bay.Also, anti-reflective coating reduces both internal and external reflections on the lenses themselves, creating a nicer cosmetic appearance. Internal reflections appear as rings that make lenses look thick. External reflections mask your eyes from a clear, complete view when someone is looking at you.
So with an anti-reflective coating, reflections are eliminated and eyeglass lenses look thinner or non-existent, and your eyes are more visible so you can make better eye contact with others.
Anti-reflective coating benefits virtually everyone who wears eyeglasses. Also, research shows wearing AR coated lenses improves night driving vision and increases comfort during prolonged computer use (compared with wearing uncoated lenses).
AR coating is especially beneficial if you choose high-index lenses. These thinner, lighter lenses reflect more light than regular plastic lenses unless anti-reflective coating is applied.
Anti-reflective coating is also beneficial when applied to the back surface of lenses in sunglasses, because it eliminates reflections of sunlight into your eyes from the lenses when the sun is behind you. (Since the purpose of sunglasses is to reduce how much light enters your eyes and because you aren’t concerned about making eye contact with others when wearing shades, there is no benefit to having AR coating applied to the front surface of sunglass lenses.)
Most premium anti-reflective coatings include a “hydrophobic” surface layer that prevents water spots from forming and makes the lenses easier to clean. Some AR coatings also include an “oleophobic” surface layer that repels skin oils and makes it easier to remove smudges from the lenses.
When cleaning AR-coated lenses, use only products that your optician recommends. Lens cleaners with harsh chemicals may damage the anti-reflective coating.
Also, don’t ever attempt to clean AR-coated lenses without wetting them first. Using a dry cloth on a dry lens can cause lens scratches. And because anti-reflective coating eliminates light reflections that can mask lens surface defects, fine scratches will be more visible on AR-coated lenses than on uncoated lenses.
If you live in a cold climate, nothing is more frustrating than having your eyeglasses fog up when you come in from the cold. This also can be a safety issue, since it limits your ability to see for several minutes until the fog clears. Lens fogging can be especially dangerous for police officers and other first responders to emergency situations.At least one eyeglass lens coating company (Opticote, Inc., Franklin Park, Ill.) has created a coating designed to eliminate this problem. Its thermally cured coating — called Fog Free — eliminates the condensation of moisture on lenses that causes fogging, keeping your lenses and vision clear when you make the transition from a cold environment to a warm one. It may also keep your lenses from fogging up during sports and other times you are hot and perspiring.Fog Free can be applied to plastic, polycarbonate and other eyeglass lenses, including high-index lenses and Transitions photochromic lenses. The anti-fog coating is applied to the lenses before they are cut to fit into your frame at the optical lab. Ask your optical retailer about pricing and availability.
Progressive lenses also provide a more natural correction of presbyopia than bifocal or trifocal prescription eyeglasses.Instead of providing just two or three lens powers like bifocals or trifocals, progressive lenses aretrue “multifocal” lenses that provide a seamless progression of many lens powers for all viewing distances.With progressive lenses, you can look up to see clearly across the room and in the distance. You can also look ahead to view your computer in the intermediate zone and drop your gaze downward to read and do fine work comfortably.And it’s easy to adapt to today’s modern progressive lenses.
A “corridor” of optimum vision runs vertically down each progressive lens. Your eye care practitioner will take careful measurements of your eyes and eyeglass frame in order to place the corridor in just the right location so your eyes can naturally access the various powers within the lens for comfortable viewing at all distances.
And progressive lenses eliminate an annoying problem caused by bifocal and trifocal lenses known as “image jump.”
With conventional bifocals and trifocals, images seem to “jump” as your eyes move past the sharply defined boundary between the distance and near parts of the lens. With progressive lenses, the transition between lens powers within the lens is smooth and seamless, letting you change focus from distance to near and back again more comfortably.
No eyeglass lenses — not even glass lenses — are scratch-proof. However, lenses that are treated front and back with a clear, scratch-resistant coating have a much harder surface that is more resistant to scratching, whether it’s from dropping your glasses on the floor or occasionally cleaning them with a paper towel. Kids’ lenses, especially, benefit from a scratch-resistant hard coat.Today, most eyeglass lenses, including high-index lenses and lenses made of polycarbonate and traditional plastic materials, have a built-in scratch-resistant coating. Since scratch-resistant coatings are sometimes optional, make sure your optician knows that you want your eyeglass lenses to include hard coating for extra durability. Also, ask about the warranty on eyeglass lenses that are treated with scratch-resistant coating versus those without the coating.Since a scratch-resistant coating can’t completely protect your lenses from wear and tear, do keep your glasses in a cushioned case, and clean them with a microfiber cloth and the cleaning solution your optician recommends.
Also, be wary of products that promise to repair your scratched lenses. These products may fill in the scratches, but it is impossible for them to make the scratches disappear so the lenses look new again.
Thin eyeglasses are attractive; thick ones aren’t. Light eyeglasses are comfortable; heavy ones aren’t. So it’s no surprise that most of us want the thinnest, lightest eyeglasses possible. Most eyeglass wearers are nearsighted, and require the basic physical property of lenses with edges that are thicker than their centers. The stronger the prescription, the thicker the edges. Hi-index-Eyeglass lenses are able to correct vision because they bend light as it passes through the lens. The amount of light-bending (or refraction) that’s needed to provide good vision is determined by the eyeglass prescription provided by your eye doctor.
Because of the ability to bend light more efficiently, nearsighted lenses made of high-index materials have thinner edges than the same prescription made from conventional plastic materials of the same prescription power.Lighter, Thinner edges require less lens material, which reduces the overall weight of the lenses. Lenses made of high-index plastic are lighter than the same lenses made in conventional plastic, so they’re more comfortable to wear. High-index glass lenses also have thinner edges, but high-index glass is heavier than conventional glass, so there is not as much weight savings with glass as there is with plastic lenses.
Lightweight lenses are even more of a benefit for farsighted prescriptions, which can make conventional lenses very heavy. And most high-index lenses also have an aspheric design, which makes them flatter and reduces the magnified “bug-eye” look that conventional lenses cause in strong farsighted prescriptions.
Light reflected from surfaces such as a flat road or smooth water generally is horizontally polarized. This means that, instead of light being scattered in all directions in more usual ways, reflected light generally travels in a more horizontally oriented direction.This creates an annoying and sometimes dangerous intensity of light that we experience as glare.Polarized sunglasses cut glare and haze so your eyes are more comfortable and you can see better.
Polarized lenses contain a special filter that blocks this type of intense reflected light, reducing glare.
Though polarized sunglasses improve comfort and visibility, you will encounter some instances when these lenses may not be advisable. One example is downhill skiing, where you don’t want to block light reflecting off icy patches because this alerts skiers to hazards they are approaching.
In addition, polarized lenses may reduce the visibility of images produced by liquid crystal displays (LCDs) found on the dashboards of some cars or in other places such as the digital screens on automatic teller (bank) machines.
With polarized lenses, you also may be unable to see your cell phone or GPS device. Boaters and pilots also have reported similar problems when viewing LCD displays on instrument panels, which can be a crucial issue when it comes to making split-second decisions based strictly on information displayed on a panel.
However, for most other sports and activities, polarized sunglasses offer great advantages. And today, many polarized lenses are available in combination with other features that can enhance outdoor experiences.
Polarized bifocal sunglasses or progressive lenses are examples of options for the presbyope who also likes outdoor sports.
And polarized photochromic lenses, which change from dark outside to light inside, may be right for the light-sensitive person who frequently is in and out of the sun on any given day.
Whether you spend your time waterskiing or boating, in-line skating or mountain biking, driving or jogging, polarized sunglasses may be the right choice to help you enjoy your life outdoors.
Another beneficial lens treatment is an invisible dye that blocks ultraviolet (UV) light. Just as sunscreen keeps the sun’s UV rays from harming your skin, UV-protective treatments for eyeglass lenses block those same rays from damaging your eyes. Overexposure to ultraviolet light is thought to be a cause of cataracts, retinal damage and other eye problems.
Regular plastic eyeglass lenses block most UV light, but adding a UV-blocking dye boosts UV protection to 100 percent for added safety. Other eyeglass lens materials, including polycarbonate and most high-index plastics, have 100 percent UV protection built-in, so an extra lens treatment is not required for these lenses.
Photochromic lenses also block 100 percent of the sun’s UV rays without the need for an added UV lens treatment.
Photochromic lenses such as those made by Transitions Optical are clear (or nearly clear) indoors and darken automatically in response to sunlight outdoors. They also protect your eyes from 100 percent of the sun’s harmful ultraviolet radiation.
These features make photochromic lenses a great convenience, because they reduce your need to wear prescription sunglasses in most outdoor conditions.
Today’s photochromic lenses come in a wide variety of lens materials. So whether you prefer polycarbonate lenses, high-index lenses, or regular plastic or glass lenses, you typically will be able to purchase a photochromic version of your preferred lenses.
When you are fitted with your first pair of progressive lenses, you may need a short adaptation period typically lasting a few minutes to a few days.This progressive lens has a typical configuration of distance, intermediate and near zones.This is because blending lens powers in progressive lenses lets you see clearly at all distances, but also causes minor aberrations in the peripheral part of the lenses (see diagram).
If you glance to the far right or left, especially when looking down, you see through these peripheral zones of the lenses and your vision may be blurred slightly. Peripheral aberrations also may cause you to experience a sensation of “swim” when you make quick head movements.
Over the last several years, progressive lens designs have been improved continually to greatly reduce peripheral aberrations. Most first-time wearers notice no problems at all.
If you do have problems with blur or “swim,” you may need to — at first — make slight head movements to look more directly at objects. But eventually these problems caused by peripheral vision disappear as you adjust.
If you have a lot of hyperopia, adapting to progressive lenses may take a bit longer than if you are only mildly farsighted or are nearsighted. But with today’s lens designs, nearly everyone can wear progressive lenses successfully.
To make sure you get the best value in progressive lenses, talk to a professional optician, who will be able to recommend a customized progressive lens solution for your specific needs and give you helpful tips on adapting to and caring for your new lenses.