How to Choose Eyeglasses

In the past there were only glass lenses available, but nowadays as the technology progresses so do lenses. Today, most of the eyeglass lenses are made of high-tech plastics which makes them lighter and less breakable. They can even come with filter to protect your eyes from ultraviolet light.

Glass Lenses

Back in the day eyeglass lenses were made of glass. Even though glass lenses offer exceptional optics, they are heavy and can break easily, potentially causing serious harm to the eye or even loss of an eye. For these reasons, glass lenses are no longer widely used for eyeglasses.

Plastic Lenses

Because of its light weight (about half the weight of glass), low cost and excellent optical qualities, plastic lenses remain a popular material for eyeglass lenses even today.

Polycarbonate Lenses

Polycarbonate lenses are impact-resistant lenses which makes them perfect for sports activities, or any work that could damage your eyeglasses. They are made of the polycarbonate material which was developed by the aerospace industry for use in helmet visors worn by astronauts. Because of its lightweight and protective features, polycarbonate is used for a wide variety of products including: motorcycle windshields, luggage, "bulletproof glass," riot shields used by police, swimming goggles and diving masks, and safety glasses.

Since the material of polycarbonate lenses is lighter than other lens types, such as glass and standard plastic, eyeglasses are more comfortable to wear and less likely to slide down your child's nose. They are also about 20 percent thinner than standard plastic or glass lenses, so they are a good choice for anyone who wants slimmer, more attractive lenses. The polycarbonate material is a natural UV filter, blocking over 99 percent of the sun's damaging UV rays without the need for special lens coatings.

This is really important for kids because they spend more time outdoors than adults. Overexposure to harmful UV rays has been associated with cataracts, macular degeneration and other eye problems later in life.

It is also important to protect children’s eyes from high-energy visible (HEV) light, also known as blue light. Long-term exposure to blue light may increase the risk of damage to the retina over time, possibly contributing to the development of macular degeneration later in life. A great option for blue light protection is polycarbonate photochromic lenses, which are clear lenses that darken automatically in response to sunlight.

However, no matter how impact-resistant polycarbonate lenses are they can be easily scratched without a protective scratch-resistant coating. Most polycarbonate eyeglass lenses come with a factory-applied, scratch-resistant coating to keep the lenses clear for as long as possible and are also, typically sold with a warranty against scratches for a specified period of time.

Polycarbonate lenses reflect more light than regular plastic lenses and these reflections can be bothersome and affect vision. Anti-reflective (AR) coating eliminates reflections off the front and back surfaces of polycarbonate lenses, giving the lenses a crystal-clear appearance and providing the best vision possible.

Trivex Lenses

Trivex lenses are the safest lenses on the market. They are made of an exceptionally clear, lightweight lens material, which translates into excellent all-day wearing comfort, so you can experience superior eye protection, sharp vision and lightweight comfort and all in the same lenses.

Trivex lenses are available in a variety of lens designs and features, including progressive lenses and photochromic lenses. Besides being called Trivex, the lens material is marketed under several alternative brand names by lens manufacturers, including NXT (Essilor), Phoenix (Hoya) and Trilogy (Younger Optics).

Trivex lens material was originally developed for use by the military in helicopter windshields and fighter jet canopies. Because of the chemistry of the material specifically for use in optical lenses, Trivex is one of the most lightweight, impact-resistant eyeglass lens materials available.

Only polycarbonate lenses rival the protection and lightweight comfort of Trivex lenses. Trivex and polycarbonate lenses have a lot in common when it comes to being exceptionally lightweight and impact-resistant which are the properties that make both lenses equally suited for safety glasses, sports glasses and other protective eyewear. But they do have their differences too. They differ in how they are manufactured and other properties. Trivex lenses are cast molded, while polycarbonate lenses are injection molded. Also, Trivex lenses have a higher Abbe value than polycarbonate lenses. This is a measure of how likely white light is dispersed into its component colors as it passes through a lens material — an optical imperfection known as chromatic aberration. Trivex lenses also have a higher tensile strength than polycarbonate lenses.

On the other hand, polycarbonate lenses have a higher index of refraction than Trivex lenses. Therefore, polycarbonate lenses will be noticeably thinner than Trivex lenses. Still, Trivex lenses are thinner than regular plastic eyeglass lenses, which have a refractive index of 1.50. Besides having excellent impact resistance, optical properties and tensile strength, Trivex lenses are exceptionally lightweight. This makes eyeglasses with Trivex lenses exceptionally comfortable to wear and reduces the risk of your glasses sliding down the bridge of your nose. The only downside of Trivex lenses is their cost. They tend to cost more than polycarbonate or standard plastic lenses.

High-index Lenses

If you want thinner, lighter lenses and eyeglasses that are as attractive and comfortable as possible then high-index eyeglass lenses are the right choice for you.

They are especially recommended if you have a strong eyeglass prescription for nearsightedness, farsightedness or astigmatism. Regular glass or plastic lenses for nearsightedness or farsightedness can be very thick and heavy. Fortunately, a variety of new "high-index" plastic lens materials that bend light more efficiently has been created. 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.

Additionally, it's a good idea to have an anti-reflective lens coating (AR coating) applied to high-index lenses. AR coating virtually eliminates lens reflections and makes high-index lenses appear nearly invisible, which means others see your eyes, not your lenses. Also, according to some studies, eyeglass lenses with anti-reflective coatings provide sharper night vision with less glare, which is a real advantage for night drivers.

Aspheric Lenses

Aspheric lenses are made with flatter curves than conventional lenses which gives them slimmer and more attractive profile. Aspheric lenses are also high-index lenses. The combination of an aspheric design with high-index lens materials creates a lens that is slimmer, thinner and lighter than conventional glass or plastic lenses. They have slimmer profile for almost all prescriptions but the difference is especially noticeable in lenses that correct high amounts of farsightedness. Lenses that correct farsightedness are thicker in the center and thinner at their edge. The stronger the prescription, the more the center of the lens bulges forward from the frame.

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Photochromic Lenses

Photochromic lenses are lenses that are clear indoors and darken automatically when exposed to sunlight. The molecules responsible for causing photochromic lenses to darken are activated by the sun's ultraviolet radiation. Because UV rays penetrate clouds, photochromic lenses will darken on overcast days as well as sunny days. Photochromic lenses typically will not darken inside a vehicle because the windshield glass blocks most UV rays. Recent advancements in technology allow some photochromic lenses to activate with both UV and visible light, providing some darkening behind the windshield.

Tints of almost any color can be applied to eyeglass lenses. Lighter, fashion tints are used primarily for cosmetic purposes to enhance a wearer's looks. Darker tints allow the wearer to use the lenses as sunglasses. Different colors can be applied to lenses for different purposes, for example yellow is usually added to a lens to enhance contrast, especially in overcast conditions. Green is sometimes used as a sunglass tint, though brown and gray are the most popular sun shades. Red is a bold fashion color and also is popular among people.

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Multifocal Lenses, Bifocals and Trifocals

Multifocal lenses are eyeglass lenses with several prescriptions all in one lens. They help you see objects at all distances after you lose the ability to naturally change the focus of your eyes due to age. Bifocal contain two powers and trifocal have three. Progressive multifocal lenses gradually change in power from the top half of the lens to the bottom, and thus contain many lens powers.

All bifocal lenses work in the same way. A small portion in the lower part of the lens contains the power required to correct your near vision and the rest of the lens is usually for your distance vision. Trifocals have three points of focus, for distance, intermediate and near vision. The intermediate segment in trifocal lenses is directly above the near seg and is used to view objects at arm's length.

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Lens Coatings

There are many different lens coatings and some of them include:

Anti-reflective (AR)

As mentioned above anti-reflective coatings can help with glare, reflections, halos around light, and make for a nicer look.

Scratch-resistant and ultraviolet (UV) protection

Also mentioned above most of the eyeglass lenses today have built in scratch-resistant and UV protection coatings.

Tinted lenses

In some cases, a light or dark hint of color on the lens can help us see better. A yellow tint may increase contrast and gray tint to your sunglasses won’t change the colors of things. A light tint can hide signs of aging around your eyes.

Mirror coatings

Mirror coating is purely for cosmetic purposes, but it does hide your eyes from view and they can be found in a range of colors like silver, gold, and blue.

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The Right Shape of Glasses for Your Face

When choosing the eyeglasses consider your face shape. Knowing your face shape will help you choose glasses that flatter the shape and color of your face, along with your own personal sense of style.

Round Face

For this type of the face long and thin frames but with rough rim and temple are recommended, wide and inclined frame type also makes your face looked long, frames with sharp out line. Colors recommended for round face types are usually cool dark colors, such as black, brown. Blue, dark brown, those colors can string your face on visual effect. Inappropriate colors are any bright colors like yellow or red, sunglasses with thin rims and temples.

Oval Face

An oval face has slightly wider cheekbones and a gentle narrowing at the forehead and jaw. This face type is most versatile to fit. Oval frames set off the sense of beauty of this group of faces, also rimless frames or frames with thin metal rims are highly recommended. Appropriate colors include most light colors.

Triangle Shaped Face

Triangle shaped faces are narrow with wide jaw so choose frames with detailing on upper portion, also the width of the glasses should be slightly wider than your jawline for balance. Browline or cat eye frames work great with this type of face. Colors like blue, purple, coffee color would make an unexpected effect.

Square Shaped Face

A square face has more angular lines with equally wide cheekbones, forehead and jaw. If you have this type of face try to choose a frame which is wider than your face, round type or rounded square type without edges, oval type can soft the outline, and adjust the whole visual effect. Tonal and lively metal frame is also able to get rid of this crudity feeling. Color recommended are brown and tan. Small and narrow frames are very inappropriate.

Heart-shaped Face

This type of face is the widest at the forehead and gradually narrows through to the jaw. Here a modified wayfarer shape works great with these features and make sure that the width is slightly wider than your forehead. Choose frames with detailing on the lower portion and also, retro pin details are also good to draw attention to the eyes.