General Lens Type & Material Information
Here at Randolph Eye Associates, we are happy to explain the different types of lenses as well as their materials.
Hard Resin (plastic)
Conventional hard resin lenses are half the weight of glass lenses and can be tinted to almost any color and density. Hard resin lenses are more easily scratched than glass but can have an optional scratch protection applied. More impact resistant than glass, hard resin lenses do not require heat treating.
Lighter, Thinner Lenses
Modern technology has created lenses that bend light differently so that stronger corrections are thinner than when made in conventional materials. Such lenses are called “high index” and stronger corrections are more attractive because they are slimmer. Glass lenses are also available with the slimming advantages of High index but are considerably heavier. High index plastic uses less material so they are often lighter in weight. High index lenses absorb all harmful UV light and can be tinted to any shade or color.
Lenses That Darken in the Sun
These are lenses that darken as you go from indoors to outdoors. They are available in both glass and lightweight hard resin. They darken to shades of grey and brown. Ask for a demonstration of photosensitive lenses.
Polycarbonate lenses are the most impact resistant lenses available and are always the lens of choice for young people and active patients. Polycarbonate lenses are high index and are usually the lightest, most comfortable lenses. They absorb all harmful UV light and can be made with ultra thin edges because of their unique strength.
For years glass was the only lens material available and glass still offers superior optics. The most scratch-resistant material, the primary disadvantage of glass is its weight, generally twice that of hard resin. Glass lenses are heat or chemically treated to increase impact resistance.
Single Vision Lenses
Single vision lenses function as all purpose glasses for people who have normal accommodation. People who normally wear bifocals or trifocals can use single vision for distance or near lenses. Single vision lenses can also function as occupational glasses for certain types of work. Single vision lenses are available in all lens materials.
These new lenses provide special visual and cosmetic benefits for stronger corrections and increase edge to edge clarity. Flatter than conventional lenses, aspheric lenses eliminate the “bulgy” appearance of strong plus lenses (far-sighted corrections) and greatly enhance the appearance of finished eyewear. People with strong nearsighted corrections also benefit from thinner, lighter weight glasses when their lenses are aspheric. Because aspheric lenses are positioned closer to the face, there is less eye magnification with farsighted corrections and less “small eyes” look with nearsighted corrections. Aspheric lenses are often made of high index materials for the ultimate in thin lenses.
Flat Top Bifocals
This is an older style bifocal form and has limited compatibility with many of today’s lens upgrades. The bifocal portion is made in a variety of widths to help with various close-up occupations. Flat top bifocals are made in every type of lens material.
Franklin Style Bifocals
Sometimes used for those who need a wide field of vision for near work (accountants, for example), Franklin style bifocals have a distinctive appearance and are thicker because of their design. They are generally only available in glass, hard resin and photochromic glass. They are being replaced by wide Flat Top bifocals.
Trifocals come in a variety of designs. Flat-top trifocals are the most widely used form. The added segment provides clear vision at arm’s length distance, the area that is usually bluffed for bifocal wearers. Trifocals are available in all lens materials.
Progressives (no line bifocals)
These lenses provide all the benefits of bifocals but add the feature of continuous clear vision at all distances, including mid-range distance (arm’s length). Progressives have the cosmetic advantage of appearing to be single vision lenses so they never reveal the user wears bifocals. Progressives are available in all lens materials and also made in aspheric form. Because of their many benefits, they are the lens of choice for bifocal and trifocal wearers.
Many occupations impose demanding visual requirements on those who wear bifocals or trifocals. Special occupational designs are available to solve these special needs. If the visual requirements of your job falls into this category, let us know and we’ll explain what will work best for your individual needs.
All sorts of special lens designs are available for the special needs of sports enthusiasts. Polycarbonate is usually the material of choice for active sports.
There are a variety of options for those who use computers. These include special filters and anti-reflection coatings.
Polarized Sun Lenses
These are the exciting sunglasses that eliminate reflected glare. They are especially appropriate for drivers, fisherman, hunters and all types of outdoors activities.
OPTIONAL LENS TREATMENTS
Scratch Protection Coating
Light weight hard resin lenses can be more easily scratched than glass lenses. Special coatings have been developed to help protect lenses from normal scratching. The modest additional cost for such scratch coating is usually a prudent investment.
It is generally accepted that the ultraviolet rays in sunlight pose potential harm to the eyes. Special treatment is available for hard resin lenses that completely blocks hazardous UV light. Lenses like polycarbonate and high index include built-in UV protection at no extra cost.
Special anti-reflective coatings are now available for spectacle lenses, much like those used for fine camera lenses. These coatings are particularly effective for reducing eye fatigue for computer operators and anyone driving at night. And, of course, AR lenses enhance appearance by removing all distracting reflections.
These are, by no means, the only lenses available. By telling us of any unusual work or leisure visual requirements, we can tailor exactly the right lenses for all your visual needs.