Progressive Lenses (No Line Multifocals)
One of the main problems with traditional bifocals is the need for intermediate areas of vision like for a phone, the dash of the car, prices on a shelf, or computer screen. On traditional lined bifocals, the near area is set at the traditional reading distance (40cm). If the object is not at that distance it will appear blurry and can cause strain. It is challenging to switch from one focusing power to another when it is separated by a hard line. Bifocals were great for several hundred years until progressive lenses were developed.
The newest variation of bifocals and trifocals is the no-line lens or digital progressive lens. Progressive lenses provide a smooth and gradual transition from far away objects to up close 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. These are also great for computer users. Up until recent years, progressive lens manufacturer technologies has limited the width of the reading area and also cause a blur or swim area out to the sides that patients did not like.
It is important to know there are currently hundreds of models of progressive lenses. 90% of the current models do not fully utilize the available technology. Only the current Free Form lenses such as the Hoya ID series and Varilux S series (consider links to pages) maximize the new technologies. This provides the widest reading area of any progressive lens and minimizes the previous blur or swim feeling off to the side of the lenses. These lenses use special digital measurements of how your frame fits your face, then computer analysis customizes the lens to match your personal measurements. The old days of using a pen to dot the pupil on lenses is over.
Lens Materials
Previously, lenses used to be made out of glass, which was heavy and had to be tempered with high heat or chemicals to prevent it from cracking. Glass lenses are scratch resistant but will easily shatter making them unsafe if an accident occurs. The next generation was plastic, referred to as CR39. This material does not shatter like glass, but it is still brittle to cracks. CR39 also requires coatings to keep it from scratching and to block UV light from damaging the eyes. At Insight Eyecare in order to best care for our patients we do not offer either of these materials due to their flaws. Our beginning lens material is called Polycarbonate, it was invented as jet plane windshields. It is thinner, lighter, stronger, and blocks UV light to protect the eyes without the need for additional temperings or coatings. The newer and better lens material called Trivex fixed the downfalls of even polycarbonate. Trivex is optically clearer, lighter weight, and is a more consistent lens material allowing for lighter lenses. This is what we recommend on our mild to moderate Rx strengths.
Higher prescriptions cause thicker parts of the lens. This can be a nuisance always pressing on the nose and ears. In order to keep high power lenses as thin and lightweight as possible, we recommend high index materials. High index materials are named because they have a higher index of light refraction. Basically, they can do the same optical job that Trivex does, but with less lens material making them thinner and lighter. No Coke bottle glasses here! Not only are high index lenses thinner, but they are also lighter and stronger, making your glasses more comfortable. When learning about high index lenses, you may hear many unfamiliar numbers and terms. Basically, remember the higher the index of refraction, the thinner the lens.
Polycarbonate: The first and still the most popular high index plastic is polycarbonate. Polycarbonate was originally developed for fighter jet cockpits. It is very strong, very light, and resistant to scratches and breaking. Safety glasses and most sports lenses are made of polycarbonate. In addition, the American Optometric Association (AOA) recommends polycarbonate lenses for all children.
Trivex: This material is the newest in the lens category. It has a mid index, but it is so light that it almost floats on water! It is a great choice for safety for impact resistant eyewear. It also works very well for rimless eyeglasses as it is one of the strongest lens materials available. *Dr. Tate’s #1 Recommendation
High-Index: High index lenses, are much thinner than regular glass, plastic, or even polycarbonate. Generally, we recommend high index with a prescription strength of 4.00 or over. Talk with our trained optician to decide which high index lens is right for you.
Anti-Reflective (No Glare) Coatings
Normal lenses often have glare, reflections, and “ghost images” off of bright lights such as fluorescent bulbs, computers, phones, headlight. Now we have a lens treatment system that can eliminate those annoyances and make lenses easier to clean and more scratch resistant. The reflections we see are a result of images reflecting off the surface of the lenses, there can be up to 4 images on the untreated lens from one light source. With untreated lenses, much of the light reflects off the lenses producing glare and reduces the wearer’s vision. In other words, the light reflections are a visual and cosmetic problem.
Anti-reflective coatings reduce 99.5 percent of reflections and the glare the lens would introduce. They make it easier for you to see and easier for others to see you. No-glare treatments are especially useful for those viewing computer screens, phones, tablets, and driving at night. The performance of anti-reflective lenses continues to improve with the arrival of the newest generation of ultra-premium anti-reflective coatings! The newest treatments take almost 20 hours to put on the lenses. Besides reducing reflections, they also make a more scratch resistant lens that is easier to clean. All of our no-glare lenses include a minimum 1 year warranty.
Photochromics (Transition Into Sunglasses)
If you are commonly outside and are bothered by bright, you should consider photochromic (transition) lenses. Photochromic lenses darken when exposed to UV rays. The change is caused by photochromic molecules that are found in a layer inside the lens. When the wearer goes outside (exposing to uv light), the lenses darken or tint. When the wearer goes back inside, the glasses become clear. This process gets faster and faster with each new generation of photochromics.
There are a variety of photochromic options available, with choices in color and darkness of tint. It is important to know ahead of time that photochromic do not darken when driving in a car because the windows of cars block UV light needed to change the lenses.
Polarized Lenses
Glare from other cars, water on the roads, and on your own windshield can make driving dangerous. It has been reported that 30 percent of wrecks site glare as a major cause. To eliminate this glare, we offer polarized lenses in both Rx and non-Rx sunglasses. Polarized lenses significantly reduce glare off of other objects, allowing better visibility and decreased eye strain so that you can drive safe. Polarized lenses are the most effective way to reduce glare off of other objects.
Interested in how these lenses work? Glare commonly comes from reflections off horizontal surfaces, so the light is “horizontally polarized.” Polarized lenses feature vertically-oriented filters known as ”polarizers.” They are a film placed in the middle of the lens when it was created, this is why we can not polarize lenses already made. These polarizers block the horizontally-polarized light, resulting in a glare-reduced view of the world. Polarized lenses are a must for for any outdoor enthusiast. Fishermen can see better through the water due to eliminating bright reflections from the water. Golfers can see the green easier, and joggers and bikers can enjoy reduced glare from the road. In addition, drivers can enjoy reduced glare off of the other cars and a safer driving experience for them and their passengers.
Bifocal Lenses
Bifocal lenses have been around for hundreds of years. A little-known fact is that bifocals were invented by Benjamin Franklin, and his style of bifocals are still available today. There are actually multiple types of bifocals, the D shaped style being the most common. Bifocals have the distance vision in all of the lens except a smaller area shaped like a sideways “D”, and found in the lower half of the lens. This D area is the near vision area usually set around 16-inches from the surface of the eye. These bifocals are commonly known as lined bifocals or flat-tops. Another popular style is the executive style lens, even though they are are less common. Executive lenses have the distance on the top half and are split horizontally down the middle of each lens with an elevated line discerning the near bottom area. It can be a challenge dealing with the sharp transition of the line on bifocals, making things like walking difficult. Thankfully science has changed since the 1700’s to develop a better type of multifocal lens, called the no-line, or progressive lens.
Trifocal Lenses
One of the negatives of bifocals is the missed intermediate area of the lens. As the eyes age a stronger prescription is needed to read, this makes the need for a mid-distance area in glasses. Without a middle are it is difficult to focus on objects at intermediate distances, such as grocery items on a shelf, your computer, or your speedometer. Thus, trifocals are necessary for an intermediate area of the lens to help with those tasks.
Trifocals, (aka lined trifocals), feature three areas of focus, each separated from the other by a distinct line. The three windows allow for focusing on distant objects, intermediate (computer/car dash), and for reading(phone/books). The downside of trifocals are the distinct lines that can affect your vision. That is why we recommend progressive lenses to allow clear comfortable vision at all distances.
