Optical Discount Centre
Types of Lenses
There are many lens types, tints or coatings that may be recommended to you at ODC . Here is a brief guide describing your lens options:
Mid-Index Lenses
New plastic materials have been developed that are thinner and therefore lighter than CR-39. Often the new materials are described by their refractive index.The higher the refractive index, the thinner the lens can be. CR-39 has a refractive index of 1.5. At ODC we sell 1.56 index lenses as our standard lens. This lens is thinner than CR-39.
High Index Lenses
For higher prescriptions even 1.56 lenses may look too thick, particulalry in semi rimless and rimless frames.Lenses are available with a refractive index of 1.6 and 1.67. These lenses are referred to as high index lenses and are priced upon your prescription.
CR-39 Plastic Lenses
Originally spectacle lenses were made from glass, making them very hard and not easy to scratch, but at the same time, heavy and easy to break. This sometimes results in wearers receiving serious eye injuries.During the early 1960's a lightweight plastic lens called CR-39 was introduced, having a similar thickness to glass lenses but they scratched easily. Hard coatings were then developed.
A hard coating is a coating applied to the surface of a plastic lens to harden the surface and reduce scratching. All lenses sold by Optical Discount Centre are hard coated for FREE.
Hard coatings harden the surface, but they do not make the lens unscratchable. CR-39 is the main lens material used today in plastic lenses.
UV Protection
All lenses sold by Optical Discount Centre filter out most UV light. Prescription sunglasses are coated for FREE, at no extra cost, with a UV coating to block all UV light.Aspheric Lenses
Aspheric lenses are made with a non-spherical curvature, making them thinner and flatter. All high index lenses sold by Optical Discount Centre are aspheric.It can take a few days to get used to wearing aspheric lenses for the first time as the curvature is different from standard lenses. But once you are used to them you will see that they give clearer and less distorted vision.
Transitions® Lenses
Transitions® lenses change colour in response to UV light, meaning that they become dark in the sunlight and lighten up indoors. Transitions® lenses block 100% of UV rays to protect your eyes from UVA and UVB radiation which could damage your eyes. They become as dark as sunglasses outdoors and about half as dark as sunglasses when inside a car.Transitions® is a registered trademark of Transitions Optical, Inc.
Anti-Reflective Coatings
An anti-reflective coating or also called multicoat, reduces the reflections visible on the lens surface. Lenses with anti-reflective coatings are excellent for night vision because they reduce the reflections caused by light reflecting off the lens surface. Unfortunately, they do not reduce glare.Anti-reflective coatings make glasses look better as the lens looks more clear, rather that having visible reflections on it. This means people can see your eyes rather than the lens in front of your eyes.
Anti-reflective coatings are made of a thin coating of material which absorbs light rather than reflecting it. Modern hydrophobic anti-reflective coatings, as used by Optical Discount Centre are easy to keep clean.
Single Stock Vision Lenses
Lenses with only one optical power. These are often reading glasses or glasses worn all the time.Bifocal Lenses
Lenses with two optical powers. There is a line separating the two powers. The top section usually is for distance vision and the bottom section is for near vision.Multifocal Lenses
Multifocals, also called graduated or progressive lenses, have no line on the lens, but the top of the lens is for distance vision and the bottom is for reading. Some people may take a few days or a week to get used to them.
"Why are our glasses so cheap?"
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