Lenses & Coatings
Normal lenses often create glare, reflections, and “ghost images.” Now that can be eliminated with an anti-reflective coating.
What we see is a result of light being sensed by our eyes. With normal glasses, much of the light reflects off the lenses. This produces glare. It also reduces the wearer’s visual acuity. In other words, the light reflections are a cosmetic and visual problem.
Anti-reflective coatings increase light transmission through the lenses to 99.5 percent. It makes it easier to see and easier for others to see you. These coatings are especially useful for those viewing computer screens and driving at night.
These lenses most people know as the lenses with the line or circle across them. They are actually 2 lenses fused together…the top portion for distance vision and the bottom portion for up-close reading. The advantage of these lenses over progressives is that they have no peripheral or “side” blur however the big disadvantage is that they give the patient no intermediate or range of vision, which is essential for computer work or any work at arms length, plus the obvious disadvantage of the visible line across them. These lenses tend to be reserved for patients who have used them successfully and happily for many years. Below is a picture of a traditional bifocal lens. There are a few designs of these lenses, pictured below is a flat top or D-seg bifocal.
Cosmetic and Specialty Tints
Your glasses don’t have to be an eyesore to those around you. Eyeglasses can be a stylish accessory, a part of your personality, or a way for you to be different. There are a variety of frames to choose from, but you may not know that there are a variety of ways to improve the appearance of the lenses, too. Cosmetic tints are now available. These tints offer a variety of colors and shades. You can choose light blue or any color under the rainbow. Some lenses are clear at the bottom and gradually get more colored towards the top of the lenses. There are many ways to adjust your lenses to whatever style suits your personality. Some tints are also functional.
Recently there has been much attention on a condition called Computer Vision Syndrome, or CVS. A special tint for your glasses can reduce eyestrain associated with CVS. There are many other tints to choose from, as well.
High Index Lenses
Previous to the last few years, the only materials available to use for lenses were glass and a hard resin called CR-39. But recently, high index lenses have become available. High index materials are named because they have a higher index of light refraction. Basically, they can do the same job that glass or CR-39 does, but high index lenses are much thinner and lighter. With high index lenses, you can avoid having “soda bottle” lenses.
When speaking about high index lenses, you may hear many unfamiliar numbers and terms. Here are a few things to remember.
The first and still 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 impact. Most sports lenses are made of polycarbonate.
Other high index materials are classified by numbers. The higher the number, the thinner and lighter the lens. The lower numbers are classified as mid-index lenses. Mid-index lenses, such as 1.54, 1.56, and 1.57. These lenses are thinner than glass, and nearly as strong as CR-39.
High index lenses, such as 1.66, 1.74, and 1.9, are much thinner than regular glass or plastic. Talk with your doctor to decide which high index lens is right for you.
Progressive lenses are typically for patients over the age of 40, and correct your vision for all distances, from infinity to up-close reading. It is for this reason they are superior to the traditional bifocal with the visible line across the lens, all of which will be explained in the next section. These lenses are probably the most important decision a patient makes regarding their vision correction, and this following section will explain why.
These lenses are called progressives because they progressively get stronger from the top of the lens to the bottom where you read up-close. There are hundreds if not thousands of designs of progressives on the market, and these lenses are like cars…they all do approximately the same job however you would rather drive a luxury car. These lenses are designed with a corridor of clear vision throughout the middle of the lens with peripheral or “side” vision blur. Typically the better lens will offer a wider corridor of vision with less peripheral blur. You probably have heard “horror” stories from friends and family about getting used to progressive lenses, this is usually due to improper fitting by the person selling you the glasses with or without the use of a poor lens design. You can buy a top of the line lens, but if not fit properly this lens will be useless to you. Having 2 opticians on hand at Advanced EyeCare with over 25 years of experience fitting these lenses you can be assured of having no problems.
Below is a rough chart that represents different categories of progressive lenses…note that as the categories get higher the amount of green (clear vision) increases. Category 1 lenses are of poor design and lead to patients having problems getting used to them therefore we do not sell them at Advanced EyeCare. As the categories increase, so does the quality of the lens and hence the quality of your vision.
If you’ve ever felt frustrated at needing prescription glasses and prescription sunglasses to accommodate an outdoor lifestyle, you should consider photochromic lenses. 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 or tint. When the wearer goes back inside, the glasses become clear.
There are a variety of photochromic options available. Depending on what you choose, you can customize the lenses to your needs. Some lenses darken only in direct sunlight, while others darken in little or no direct light. Some are designed to darken while you’re in the car to reduce road glare while you’re driving. You can even choose the color of the tint. Ask your doctor what options are available.
Light reflected by shiny transparent materials is eliminated by a polarization filter. Glare off of water, snow, roads, or any reflective surface is eliminated by a polarized sunglass filter. With polarized glasses, the sea even seems more transparent!
Did you know…
- Natural light waves bounce around in all directions
- When light waves hit reflective surfaces, they become “polarized”
- Polarized light waves move in a horizontal direction. Polarized light causes harsh, blinding glare
- Glare impairs vision and hampers concentration when driving and playing sports. It can also lead to headaches and eyestrain
- Polarized lenses have a vertical filter which eliminates the glare from the horizontal polarized light
Whether enjoying the outdoors, playing sports or driving your car, polarized lenses enhance vision by increasing visual clarity and improving color and depth perception under all circumstances.
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 as well as their performance. With a scratch resistant coating, you don’t have to worry so much about minor scratches on your lenses.
Another advantage of scratch resistant coatings is that most coatings come with a one-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.
Everybody over the age of 40 starts to have difficulty reading small print. This is not a disease but a natural ageing process of the eye. The average patient will use either prescription reading glasses, drug-store readers, monovision contact lenses or bifocals. These are all fine options however in today’s technological world most of work with computers, we may need a specialty lens in order to cope with hours of near work. Traditional bifocals, monovision contacts, drug-store readers and prescription readers give no range of vision, meaning that the computer screen may be clear however objects slightly farther or closer than the screen will be out of focus. This is where specialty lenses come in. These lenses have slightly different prescriptions throughout the lens, which will give you a comfortable and clear range of vision…making them ideal for most office situations, or any situation in which you work at close objects for extended periods of time. Please ask the doctor or one of the staff regarding these lenses.
Bifocals allow the wearer to read through one area of the lens, and to focus on distant objects through another area of the lens. As the eyes age, though, a stronger prescription is 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, intermediately distanced objects, and for reading. The downside of trifocals is dealing with the lines between the different focusing powers. Fortunately, recent advances in technology have led to developments in no-line, or progressive lenses.
Single Vision Lenses
Single vision means that glasses are designed to correct for hyperopia (farsightedness), myopia (nearsightedness) or presbyopia (needing reading glasses after age 40) all of which may include astigmatism. Basically, single vision means any glasses that do not include a bifocal prescription. In most cases, any prescription for a patient under the age of 40 will be single vision. For “low” prescriptions (under + or – 4.00), an average plastic lens (CR-39) will be the lens of choice. For prescriptions over + or – 4.00 you would want to go for a thinner lens which would look better in the frame as well as decreasing the magnification of your eyes (in a farsighted prescription) or minification of your eyes (in a nearsighted prescription).
Lenses have a number assigned to them, which is called their refractive index, this will determine how thick or thin a lens is. Below is a brief list of the main lens options.
- 1.498: average plastic lens, thickest option, fine choice for under + or – 4.00
- 1.59: 20% thinner and 25% lighter and stronger than the average plastic lens, fine for under + or – 6.00
- 1.67: thinner again, fine for under + or – 10.00
- 1.74: thinner again, fine for under + or – 14.00
- 1.9: the thinnest lens in the world, fine for any high prescription, made of glass therefore not recommended for children
Other lens options include scratch resistance coatings, anti-reflection coatings, U.V. protective coatings, colored tints, and polarized tints, which prevent glare.
Having 2 licensed dispensing opticians on hand will make lens choice an easy and confident decision.
The ultimate in lens protection! Crizal lenses with Scotchgard Protector stay much cleaner for much longer. The outstanding clarity of Crizal anti-reflection and anti scratch lenses has been improved. It is now protected by Scotchgard Protector, the worlds leading protective brand.
Dust won’t stick during cleaning. Rain and grease slide off. With no glare, smudges, dust, dirt, oil, water or grease you will see as clearly as you did the first day you bought your new lenses. People will notice your eyes through your lenses rather than unsightly reflections on the lens surface.
Transitions lenses have made vast improvements throughout time. Remarkably clear indoors and dark outdoors, Transitions lenses are a wonderful option for patients of any age.
Note: Transitions Lenses are activated by UV rays. This means they will not fully darken in your car. Reason being, your windshield blocks out the majority of ultraviolet wavelengths.
Even without tinting or darkening your lenses, you can protect your eyes from harmful ultraviolet rays from the sun. Most people wear sunblock on their skin, yet never consider protecting their eyes.
Ultraviolet rays are invisible and are prominent even on cloudy days. Therefore, it is important to protect your eyes during all daylight situations.
Many lenses, such as high index, ultralite, polycarbonate and Transitions lenses have built-in UV protection.