Learn more about the various types of lenes, what materials lenses can be made from and the eyeglass lens treatments available today:
A recent variation of bifocals and trifocals is the no-line lens or progressive lens. Progressive lenses provide a smooth transition because they do not have a distinct line which separates the focusing powers. Instead, a gradual change in power allows the wearer to focus on objects at all distances. Distant objects are viewed through the upper portion of the lens, while near objects are viewed through the middle or lower portion of the lens.
No one else has the same combination of head and eye movements that you do. In depth scientific research has shown that each of us has a unique combination of head and eye movement that begins in childhood, and is hard to change as an adult.
Our office has a special instrument that can measure your head and eye movements. This gives us the ability to customize the lens to your specific visual needs.
Single Vision Lenses
Single vision lenses have the same focal power throughout (top to bottom) and can be used to correct nearsightedness, farsightedness, astigmatism, or a combination of these disorders. Most people who wear glasses before the ages of 35 to 45 have single vision lenses.
For many people, different lenses are needed for seeing at different distances. Bifocal lenses have two parts: the upper part normally used for distance vision and the lower part used for near-vision tasks such as reading. Many people after reaching age 35 to 45 develop a condition called presbyopia, which is the deterioration in the ability of the eye’s natural lens to expand or contract in order to focus on close objects. People with presbyopia need a prescription lens for reading and may need a different lens for seeing in the distance. Benjamin Franklin invented bifocals so he wouldn’t need to switch glasses when reading. They serve that same purpose today.
In most bifocals the “reading” area is smaller, and found in the lower hemisphere of the lens. The segment for near-vision correction can have one of several shapes:
- Half-moon, or flat-top segment shaped like a sideways “D”,
- Round segment
- Narrow rectangular area called a ribbon segment
- The entire bottom half of the lens, in what is called variously the Franklin, Executive.
One thing that is difficult about using bifocals is dealing with the line between the two vision areas. Fortunately, recent technologies have developed a new type of lens, called the no-line, or progressive, lens.
As the eyes age, though, a stronger prescription is often needed to read. This would be fine, but the stronger prescription that allows for reading makes it difficult to focus on objects at intermediate distances, such as grocery items on a shelf or your speedometer. Thus, trifocals are necessary for a third prescription for intermediate focusing.
Trifocals, also known as line trifocals, feature three areas of focusing power, each separated from the other by a distinct line. The three windows allow for focusing on distant objects, intermediate distance objects, and for reading. As with bifocal lenses, the downside of trifocals is dealing with the lines between the different focusing powers.
With the addition of progressive lenses we are now able to reduce the difficulty created by wearing trifocal or bifocal lenses.
We all have heard the phrase, “Different strokes for different folks.” Well, this also holds true when it comes to selecting glasses. There are different lenses for just about everybody. No matter what your particular need, there is probably a specialty lens designed for you.
- Computer Lenses: are lenses designed for viewing your computer screen and documents on your desk. The lenses are designed to reduce Computer Vision Syndrome, or CVS, which can be characterized by headaches, eye strain, neck and back aches, dry eyes, blurred vision, and double vision.
- Double Bifocals: are sometimes prescribed for people who need close vision overhead. These lenses have a reading area at both the top and the bottom of the lens and are often helpful to pilots, electricians, and others who need clear near vision when looking up as well as down.
Other specialty lenses include custom designs for sports and other recreational activities.
High Index Lenses
Previously lenses were made from either glass or a hard resin called CR-39. Currently lenses are available in materials that are called high index lenses. High Index materials have a higher index of light refraction which allows for them to be much thinner and lighter. These lenses enhance the appearance of your glasses as well as the comfort of them.
Here are examples of Hi-Index materials:
- Polycarbonate: The first and still the most popular high index plastic is polycarbonate. Polycarbonate was originally developed for fighter jet windshields. It is very strong, very light, and resistant to scratches and breaking. Most sports and children’s lenses are made of polycarbonate.
- Mid-Index: Other high index materials are classified by the index of refraction. The higher the number (index of refraction) the thinner and lighter the lens. The lower numbers are classified as mid-index lenses, such as 1.54, 1.56, and 1.57.
- High-Index: High index lenses, such as 1.60, 1.66, 1.74, and 1.9, are much thinner than regular glass or plastic.
Talk with our lens specialist to decide which lens is right for you.
Lens Coating & Tints
Normal lenses often create glare, reflections, and “ghost images.” That can be eliminated with an anti-reflective coating.
What we see is the result of light being sensed by our eyes. With normal glasses light reflects off the lenses which produces glare that can cause visual discomfort and decreased visual acuity.
Anti-reflective coatings increase light transmission through the lenses to 99.5 percent. They make it easier for you to see, easier for others to see you and it improves the cosmetic appearance of your eyewear. These coatings are especially useful for those viewing computer screens and driving at night.
Scratch Resistant Coating
If you have hard resin lenses (CR-39), you should consider getting a scratch resistant coating. Resins and plastics are more susceptible to scratches than glass. Scratches damage the cosmetic look of the lenses and compromise your vision. With a scratch resistant coating, you do not have to worry as much about minor scratches on your lenses.
Another advantage of scratch resistant coatings is that we give a two-year warranty. They are a great investment to prevent minor scratches. However, it is important to remember that scratch resistant does not mean scratch-proof. All lenses are susceptible to scratches.
- Mirror-Coated Lenses: are coated with a layer of reflective material that greatly reduces the amount of light entering the eyes. Mirror coatings come in a number of colors and are highly reflective. They usually are applied on sunglasses. Skiing, water sports and simply cosmetic use are good examples of where mirror coated lenses are recommended by our lens specialist.
Cosmetic and Specialty Tints
Eyeglasses can be a stylish accessory, a part of your personality, or a way for you to be unique. By adding a cosmetic tint to your glasses you can improve the appearance of the lenses. These tints offer a variety of colors and shades. Some lenses are clear at the bottom and gradually get more colored towards the top of the lenses. Many of these tints will enhance your visual performance.
Photochromic lenses darken when exposed to UV rays. The change is caused by photochromic molecules that are found throughout the lens or in a coating on the front of the lens. When the wearer goes outside, the lenses darken. When the wearer goes back inside, the glasses become clear. Because photochromatic lenses are not effective when driving a vehicle sunglasses are recommended.
Glare from wet roads, snow, light reflecting off other vehicles/objects, and glare from your own windshield can be annoying and dangerous. To eliminate this glare, we offer polarized lenses. Polarized lenses eliminate almost all glare, reducing eye strain and increasing visibility. Polarized lenses are the most effective way to reduce glare.
- “Drive Wear” is a new innovation in photochromatic/ polarized lenses.