Lens selection can be confusing at times. Not to worry, our Opticians have decades of experience and will make the lens selection process fun and easy for you. We will help you select the best lens for your brand new pair of glasses!
In general eyeglass lenses are divided into two broad categories: single vision and multifocal. Multifocal lenses can be subdivided into progressive, bifocal and trifocal.
Common Types of Lenses
Single Vision Lenses
Single vision lenses are prescribed if you need correction for one field of vision, either for distance, intermediate (computer), or items up close (near vision). Single vision has the same optical focal point or correction over the entire area of the lens.
Progressive / No-Line Bifocal Lenses
Progressive or invisible (no-line) bifocal lenses provide a smooth transition from distance correction to near correction, eliminating segment lines and allowing clear vision at all distances, including intermediate; roughly arms’ length.
Progressive lenses are the most exciting and technologically advanced spectacle lenses available. If you’re a 40-something who has trouble reading fine print, you have more lens options than the old lined bifocals your parents wore. Progressive lenses, sometimes called "no-line bifocals," are multifocal lenses that eliminate the lines of a bifocal lens. They look exactly like single vision lenses so nobody will know you are wearing a bifocal lens.
Progressive lenses continue to increase in popularity and are now the most widely purchased lenses to correct presbyopia (the worsening of near vision with age). Progressives provide a more natural correction of presbyopia than bifocals. They are considered "multifocals" because there is a seamless progression from distance to near with an intermediate section in between. This provides many focal points in order to satisfy almost any visual need.
With progressives you can look up to see clearly across the room or down the street while driving. You can also look ahead to see your computer or someone sitting across the dinner table through the intermediate section. If you drop your gaze downward, you can read fine print comfortably through the bottom of the lens.
There is a corridor that runs vertically down the middle of the lens. When fitting a progressive lens your Optician will take measurements to fit the corridor in the right place so all powers can be accessed comfortably.
Progressives also eliminate a problem called "image jump" which is experienced with bifocal lenses. The lines on the lenses create a drastic change in power which causes images to appear to jump as you move from distance to near. Progressives create a smooth, more comfortable transition from distance to near and back.
With a bifocal, the upper part of the lens is generally used for distance vision, while the lower part is used for near vision. Usually, a segment line separates the two. Typically a person with myopia (nearsightedness) would have one section of a prescription lens that has a certain diverging power while another section of the lens would have a lower diverging power for close-up work. Similarly, a person with hyperopia (farsightedness) would have one section of the lens with a certain converging power and another section with a greater power for close-up work.
Trifocal lenses are similar to bifocals, except that the two focal areas are separated by a third middle area with intermediate focus correction. This area is used for intermediate vision; roughly at arms’ length, e.g. computer distance. This lens type has two segment lines, dividing the three different correcting segments.
Most people refer to this lens type as a plastic lens. The patent of CR-39 allyl diglycol carbonatemonomer in 1945 marked a key milestone in the history of the optical industry. This new optical monomer inspired a great deal of creativity and ingenuity, which led to many of the great plastic lens products available today.
High-index eyeglass lenses are the right choice if you want thinner, lighter lenses and eyeglasses that are as attractive and comfortable as possible. Thinner, lighter high-index lenses are especially recommended if you have a strong eyeglass prescription for nearsightedness, farsightedness or astigmatism.
Most eyeglass wearers are nearsighted, which requires corrective lenses that are thin in the center but thicker at the edge of the lens. The stronger the prescription, the thicker the edges. Most of today’s fashionable eyewear frames are made of plastic or metal with rims thinner than the lens itself. Also, popular rimless mountings mean that the edges of the lenses are completely exposed. In either case, the lens edges are highly visible, and thicker edges can detract from the appearance of your eyewear.
If you are farsighted, you need "plus" (+) lenses, which are thicker in the center and thinner at the edge. Regular glass or plastic lenses for high amounts of nearsightedness or farsightedness can be quite thick and heavy. Fortunately, chemists have created a variety of new "high-index" plastic lens materials that bend light more efficiently. This means less material can be used in high-index lenses to correct the same amount of refractive error, which makes high-index plastic lenses both thinner and lighter than conventional glass or plastic lenses.
Your eyeglass prescription determines what kind of high-index material you might want for your lens. The highest index materials are used primarily for the strongest prescriptions. Rely on your Optician’s advice regarding which index to use. Your Optician will explain which high-index lenses are the best choice for your needs and budget.
Polycarbonate lenses have become the standard for safety glasses, sports goggles and children’s eyewear. Polycarbonate was developed in the 1970s for aerospace applications, and is currently used for the helmet visors of astronauts and for space shuttle windshields. Eyeglass lenses made of polycarbonate were introduced in the early 1980s in response to a demand for lightweight, impact-resistant lenses.
Because they are less likely to fracture than regular plastic lenses, polycarbonate lenses also are a good choice for rimless eyewear designs where the lenses are attached to the frame components with drill mountings.
Eliminate Reflections and Glare
Anti-reflective coating (also called AR coating or anti-glare coating) improves both your vision through your lenses and the appearance of your eyeglasses. Both benefits are due to AR coating’s ability to eliminate reflections of light from the front and back surface of eyeglass lenses. Today’s modern anti-reflective coatings can virtually eliminate the reflection of light from eyeglass lenses, allowing 99.5% of available light to pass through the lenses and enter the eye for good vision.
Anti-reflective coating reduces the glare that you see, as well as the glare that others can see on your lenses. By eliminating reflections, AR coating also makes your eyeglass lenses look nearly invisible so people can see your eyes and facial expressions more clearly. Anti-reflective glasses also are more attractive, so you can look your best in all lighting conditions.
The vision benefits of lenses with anti-reflective coating include sharper vision with less glare when driving at night and greater comfort during prolonged computer use (compared with wearing eyeglass lenses without AR coating).
Anti-reflective coating also is a good idea for sunglasses, because it eliminates glare from sunlight reflecting into your eyes from the back surface of tinted lenses when the sun is behind you.
Improve your Night Vision
Anti-reflective eyewear is particularly beneficial when driving at night. The anti-glare lens coating reduces the halo effect that occurs around headlights and streetlights in the dark. A number of light sources can affect our vision when driving such as bright sunlight, headlights and reflections on spectacles or the windscreen. Spectacle lenses without anti-reflective coating can cause vision problems due to distracting reflections, for example on wet roads and oncoming traffic. This is an additional safety risk, even for drivers with perfect vision. Anti-reflective coating significantly reduces these distractions and ensures better, clearer vision day and night. Spectacle lenses with an anti-reflective coating are recommended for drivers who often have to drive at twilight and at night in particular, as they provide the most relaxing and glare-free vision available.
Anti-reflective coating often comes with scratch coating on top of AR coating. Alternatively a scratch-resistant coating can be applied separately. No eyeglass lens material – not even glass – is scratch-proof. However, a lens that is treated front and back with a clear hard coating does become more resistant to scratching, whether it’s from dropping your glasses on the floor or occasionally cleaning them with a paper towel. To safeguard your investment in your eyewear, scratch-resistant coating should be considered for all eyeglass lenses. The only exception is glass lenses, which are naturally hard and scratch-resistant. By choosing an anti-reflective coating treatment on your lenses you will protect them against scratches from everyday use.
Transitions or Photochromic Lenses
Photochromic lenses are clear (or nearly clear) indoors and darken automatically in response to sunlight outdoors. They also protect your eyes from 100% of the sun’s harmful ultraviolet radiation.
Today’s photochromic lenses come in a wide variety of lens materials. So whether you prefer polycarbonate lenses, high-index lenses, or regular plastic lenses, you typically will be able to purchase a photochromic version of your preferred lenses.
One limitation of photochromic lenses is they do not darken adequately inside a vehicle for driving in sunny conditions. This is because they require exposure to the sun’s invisible UV rays to activate the darkening process, and most car and truck windshields block UV radiation.
There are many ways to customize your eyeglasses to fit your unique look. One simple way is to add lens color to match your frame or to enhance your vision. Sunglass lenses are tinted to cut down on overall brightness and enhance terrain definition.
Your choice of tint color affects your vision by influencing
There are several general rules to follow. For any sport or activity in bright sunlight you need a sunglass tint color that blocks most of the light such as brown, green, or gray.
If it is not a bright sunny day then you can consider lighter tint colors. The lighter tints offer less overall brightness protection but do provide excellent depth perception and enhance contrast which make them a great choice for all snow sports and off road cycling as well as other sports.
If you are considering the lighter sunglass tint colors make sure the color distortion is not a problem for your activity such as on road driving. Among all types of tinted sunglasses, gradient tint sunglasses are quite special that they have different degrees of darkness from the top to the bottom. Rose tint sunglasses, gray tint sunglasses and some others all use tinted lenses that have a uniform darkness across the entire lens. Dissimilarly, a gradient tinted lens has a dark tint at the top, and fades gradually to little or no tint at the bottom. This design allows the lens to block more sunlight coming from above, without blocking too much light from straight ahead or below. A variation of this design is double gradient tint lens, which has a darker tint at the top and bottom, and a medium tint in the center part.
However, polarized lenses are by far better than just a lens tint. See the polarized lenses section further down.
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% for added safety. Other eyeglass lens materials, including polycarbonate and most high-index plastics, have 100% UV protection built-in, so an extra lens treatment is not required for these lenses.
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 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 for greater durability.
Today, most eyeglass lenses, including high-index lenses and lenses made of polycarbonate, 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.
To keep your glasses looking new, store them in a cushioned case when not in use, and clean your lenses with a microfiber cloth and the cleaning solution your Optician recommends.
Also, be wary of products that promise to repair 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.
Polarized sunglasses have been popular for years with boaters and fishermen who need to reduce reflected glare from the water surrounding them.
But now that many others who spend time outdoors have discovered the benefits of polarized lenses, interest in these types of sunglasses has soared. Besides boaters, outdoor enthusiasts who benefit the most from polarized sunglasses include skiers, bikers, golfers and joggers, all who may enjoy a clearer view along with elimination of glare.
These sunglasses can be used for driving and, in fact, can reduce glare from a long, flat surface such as the hood of the car or the road’s surface.
Polarized sunglasses also can be worn indoors by light-sensitive people, including post-cataract surgery patients and those continually exposed to bright light through windows.
How do polarized lenses work?
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.