Types of Lenses
Considering a particular eyesight disorder, a different rx lens can be prescribed. Opticians distinguish 4 types of prescription lenses: single vision, bifocal, trifocal and progressive.
Single Vision Lenses - provide all-purpose vision patients. They have one fixed field of focus at either distance vision, intermediate vision, or near vision.
How do prescription bifocal work?
A bifocal lens is really two lenses combined into one. Bifocals have a single visible line separating the two viewing zones. The upper part of the line bi-focal lenses correct distance vision and the lower part is for near vision. The driving distance area is designed like a single vision lens, while the near area contains the distance prescription and the additional amount of plus spherical power needed to see at a reading distance. The additional amount of plus power (also called ADD power), for reading is located in an area referred to as the segment.
Trifocals are lenses with three points of focus: usually for distance, intermediate and near. Trifocals have an added segment above the bifocal for viewing things in the intermediate zone, which is farther than the near zone: about arm's length away. Computer terminals are generally in the intermediate zone. A common style is the 7x28 flat-top or D-shaped segment, 28 mm wide, with a 7 mm high intermediate segment. Larger intermediate segments also available. Trifocals are becoming rarer as more people choose to wear progressive lenses.
Motorists who need to be able to see in the distance to drive as well as to see the gauges on the dashboard and to read a map also would benefit from a trifocal lens in order to see things in the distance, the intermediate and the near areas.
What is progressive lens?
A progressive lens make a progressive change from distance vision to near vision providing an infinite range of powers in between. An additional advantage of progressive lenses is the lack of a bifocal line. They are attractive and provide you with a gentle progression of correction from the top of the lens to the bottom.
Progressive addition lenses avoid the discontinuities in the visual field created by bifocal and trifocal lenses. The lenses are also more cosmetically attractive. The lenses suffer the disadvantage of creating regions of aberration away from the optic axis, yielding poor visual resolution. Although manufacturers are constantly striving to minimize these distortions, some wearers cannot tolerate the lenses. Over the past years manufacturers have been able to minimize the aberrations by using a wide array of mid and high index materials as well as new wave-front freeform technology.
Progressive Lenses- provide seamless vision at all distances. These lenses are variable focus with no visible lines, and provide a more natural visual solution then either of the lined multifocal solutions. Progressive lenses vary widely in price and in quality of lens design. Today there are as many as 60 different brands of progressive lenses available, with varying levels of advantage and disadvantage. The newer lens designs available have made great strides in ease of adaptation, ease of use, and wearer comfort; successfully addressing the disadvantages of older lens designs, many of which are still currently available. Progressive lenses offer the best all-around, daily use solution to people needing help at all distances.
Please Read this before purchasing Progressive Lenses: Progressive lenses are sometimes called "no-line" bifocals. Progressive lenses are basically trifocals without any visible lines. Progressive lenses were developed because many people wanted the convenience of not having to change their glasses to read, but they did not like other people to see the visible line. Progressive lens design: Progressive lenses offer the convenience of multifocals, but without the visible line. However, progressive lenses are much harder to use and to adapt to than bifocal or trifocal prescription glasses, and they are much more expensive. In order to create a no-line progressive lens, there are two large areas of the lens that you cannot see through. Imagine what an hourglass looks like. This is the shape of the area of the progressive lens that you can see through. Objects seen through the areas of the lens to the left and right of the narrow middle section are highly distorted and you cannot see through them. The bulge areas at the bottom and top of the lens are for near and distance vision, and the thinner "corridor" connecting them is for intermediate distances. On either side of the narrow portion of the hourglass objects will appear blurry. In general, more expensive progressive lenses like Varilux® lens have a wider corridor, and less expensive lenses have a narrower corridor that can restrict the viewing area considerably. On smaller lens sizes, it is necessary to slice off a portion of the bottom (reading section) of the lens in order to install the lens in the frame. As a result, the smaller the frame size, the smaller will be the reading portion of the lens. Adapting to progressive lenses In order to use a progressive lens, you must learn to move your head to see things; you cannot just move your eyes because you will be looking through a blurry part of the lens. This is called "adapting" to the lens. Most people can adapt within a month, but some people never adapt. It is common to experience dizziness and headaches during the time that you are adapting. Getting accustomed to progressive prescription glasses can be difficult, and you must have proper instruction by an eyecare professional. Sometimes, people who try progressive prescription lenses for the first time have a difficult time learning to look through the appropriate portion of the lens at the right time. Often a simple fitting adjustment to your prescription eyewear by your local optical professional can make all the difference.
Some people still have several pairs of glasses, one for each task or distance, with specific glasses for reading, computer use, and television watching. The overwhelming majority has already switched to Progressive Glasses. And when the sun is shining people definitely need a good pair of Progressive Sunglasses! There are a variety of options available to meet your specific progressive lens needs, including thin and light no line bifocal lenses, impact-resistant polycarbonate progressive eyeglass lenses, even adjustable tint lineless bifocal lenses.
Task Specific Lenses- are any lenses made to provide a unique solution to a specific problem. Hobbyists, computer users, auto mechanics, radiologists, pool players, musicians, golfers, etc., etc... each has specific and unique problems in their visual requirements. For each there is a unique solution not normally used for daily wear. These may include lenses that have bifocals above AND below the eye for people who work over their heads; a bifocal segment located in the outer periphery of the glasses so golfers can have an unobstructed view of the ball while still being able to see a scorecard. Specially design progressive lenses which concentrate on the distances between 12 inches to 10 feet for pool players, office workers, computer users, etc.
Please send us an e-mail if you need any other type of lens.
Protective eyewear is beneficial to those who are working with or those who might be exposed to ultraviolet radiation, particularly short wave UV. Given that light may reach the eye from the sides, full coverage eye protection is usually warranted if there is an increased risk of exposure, as in high altitude mountaineering.
High intensities of UVB light are hazardous to the eyes, and exposure can cause welder's flash (photokeratitis or arc eye) and may lead to cataracts, pterygium, and pinguecula formation.
Ordinary, untreated eyeglasses give some protection. Most plastic lenses give more protection than glass lenses, because, as noted above, glass is transparent to UVA and the common acrylic plastic used for lenses is less so. Some plastic lens materials, such as polycarbonate, inherently block most UV. There are protective treatments available for eyeglass lenses that need it which will give better protection. But even a treatment that completely blocks UV will not protect the eye from light that arrives around the lens.
Glass and plastic can be coated to diminish the amount of ultraviolet radiation that passes through.
Ultraviolet UV Protection
Ultraviolet light can't be seen by the human eye. Studies suggest that UV rays can be harmful to your vision. UV is commonly divided into two types: UV-A and UV-B. All eyewear sunglasses, prescription and nonprescription glasses should block a minimum of 95 percent of UV-A rays. UV-A light is less intense than UV-B, but, UV-A penetrates deeper into the eye than UV-B. UV-A is what causes aging. UV-B light is what causes sunburn of the skin. It can damage the cornea and lens of the eye. Polarized, high index and polycarbonate lenses include 99%
Glare is the result of excessive contrast between bright and dark areas in the field of view. Light shining into the eyes of pedestrians and drivers can obscure night vision for up to an hour after exposure. Caused by high contrast between light and dark areas, glare can also make it difficult for the human eye to adjust to the differences in brightness. Glare is particularly an issue in road safety, as bright and/or badly shielded lights around roads may partially blind drivers or pedestrians unexpectedly, and contribute to accidents.
Polarized lenses are the most effective way to cut down reflected glare. Regular tinted sun lenses reduce the amount of visible light, but they offer no protection against glare a major source of discomfort and distortion of your vision when you are in the sun. They work particularly well to shield your eyes from reflections off water, snow or shiny objects. For those who drive a car, work and play in the sun, there are no better lenses than polarized!
Tints reduce visible light. Brown, green and gray tints are most common for sunglasses. Rose or pink help people who work in an environment with fluorescent lighting. Fashion tints may also complement your facial tones and make your glasses look more attractive on your face. Coordinating your frame color with the tint color provides a fashionable look.
Anti-reflection, or "AR" coatings are the most common type of optical coating in the world. Applied to elements from eyeglasses and camera lenses, to components used in high-power laser systems, AR coatings are designed to minimize natural back reflections that could otherwise interfere with the preferred operation of an optical system
Opticians dispense "anti reflection lenses" because the decreased reflection makes them look better, and they produce less glare, which is particularly noticeable when driving at night or working in front of a computer monitor. The decreased glare means that wearers often find their eyes are less tired, particularly at the end of the day. Allowing more light to pass through the lens also increases contrast and therefore increases visual acuity.
Many anti-reflection lenses include an additional coating that repels water and grease, making them easier to keep clean. Anti-reflection coatings are particularly suited to high-index lenses, as they reflect more light without the coating than a lower-index lens. Additionally, high index materials can generally be coated easier and cheaper than lower-index ones.
Excessive scratching caused by everyday use of eyeglass lenses can compromise your vision and detract from your appearance. Scratch-resistant coatings (also known as a "hard coat") can be added to the front and back surfaces of your lenses to increase their scratch resistance and durability and protect the investment you've made in your eyewear.
The basic lens we offer is lighter weight than traditional glass. It is coated with a scratch resistant material to make it last longer than uncoated lenses. It has a wide availability of prescription types to fit almost any need, plus it is easily tintable to get the custom look you want.
Be careful even with anti-scratch coating because it's still softer than glass and will scratch if you don't care for your lenses properly. It’s scratch resistant, not scratch proof coating.
No matter what coatings you choose for your glasses, you will still need to handle them with care, since no coating can make your lenses completely scratch proof.
A corrective lens is a lens worn on or before the eye, used to treat myopia, hyperopia,astigmatism, and presbyopia. The most common types of corrective lenses are eyeglass lenses and contact lenses.
Myopia (near sightedness) requires biconcave or diverging lenses, whereas Hyperopia (far sightedness) requires biconvex or converging lenses.
Corrective lenses are usually prescribed by an optometrist. The prescription consists of the necessary corrections for refraction errors in each eye, individually for distance and near vision.
How can I determine which shape and style frame will look best on me? There are so many choices of frame styles today; different shapes, different materials, different colors. To find the shape that's right for you, look at the structure of your face. The right frame will contrast the shape of your face, repeat your best feature and be in scale with the size of your face.