Eye Lenses Terms
HELPFUL EYE LENSES TERMS
Polarized lenses- Most safety glasses are not polarized, however, they are 99.9% UV protected, but polarized lenses block out harmful UV rays while allowing specific un-harmful lights in for great visibility (used primarily for fishing).
UV A Rays- Though All safety glasses are 99.9% UV A protected UV-Rays May produce severe reactions to all layers of the cornea.
UV B Rays- These UV-B may cause permanent cataracts. All safety glasses are 99.9% UV B protected.
UV C Rays- Only specialized safety glasses meet UV C standards. Which may produce photo keratitis.(welder's flash).
Lens Coatings- Depending on the coating applied, coatings protect your lenses from scratches, fogging, breakage and uv rays,
Polycarbonate Lenses- These lenses are tough, transparent lenses with high impact strength. All selections of safety glasses have polycarbonate lenses
Wrap-around Lenses- The wrap around safety glasses are OSHA approved even though they don't have side shields. Lenses wrap around to provide more protection than normal safety lenses.
Side Shields- Shields attached to the side of safety glasses for added eye protection.
Z87.1 Standards- All safety glasses must conform to the Safety standards for impact resistant lenses and frames.
UV Protection- Protection against the harmful UV rays.
CSA- These are the Canadian Standards Association-that are responsible for certifying manufacturers products or services to their published requirements.
Adjustable Temples- Temples adjust for comfort and tight fit for the person wearing them.
Ratchet Temples- Temples adjust for comfort and tight fit for the person wearing them.
Impact Resistant Lenses- These are hard, treated lenses that meet or exceed safety standards for impact resistance against debris and breakage.
Vermilion Lens- These are the rose color safety glasses, Vermillion lenses reduce glare, amplify light, block blue light, and are especially great for glass cutting and sheet metal work.
Amber Lens- The amber glasses are synonymous with the yellow lens. Amber lenses reduce glare and amplify light. They are great for low light environments.
Welding Lens- Welding lenses come in two shades, 3.0 and the 5.0. They are the darkest of safety shades and work well for light gas and arc welding.
Clear Lens- Clear lenses are a general purpose lens that provide maximum protection and visibility.
Fog-Free Lenses- The fog free lenses are great for humid environments or unstable climates, and work great for moving from one extreme to another.
Mirrored Lenses- Mirrored glasses are just as dark as the smoke lenses, they just have a different appearance when on the outside looking in. The Mirrored lenses reduce eyestrain outdoors and in sunny environments while protecting the eyes.
Smoke Lenses- The smoke lenses are similar to a sunglass lens as far as appearance, but Smoke lenses greatly reduce eyestrain in sunny environments but also allowing visibility in dark environments.
Sunglasses- Sunglasses provide protection from harmful light rays; however, they are not impact resistant like a safety glass.
Safety glasses- Protect the eyes from flying debris, chemicals and harmful lights. All safety glasses must conform to Z87.1 standards, and should have a small (Z87.1) mark on the lens or the frame.
Prescription safety glasses- While these glasses protect the eyes from flying debris, chemicals, and harmful UV rays, they also have prescription lenses or prescription inserts.
Espresso Lens- The espresso lens is brown tinted lens, very similar to the smoke lens Greatly reduces eyestrain in sunny environments but also allows visibility in dark environments.. Most Uvex brand glasses use the espresso lens; however, the web-site describes the lens as a smoke to avoid confusion.
Copper Blue Blocker Lens- Great for haze and fog situations as they provide ultraviolet protection, filters in select blue wave to help vision.. The lens looks brownish and shaded; however, it intensifies the outdoor light much like the amber and vermilion lens.
Uvex- A name brand manufacturer of safety glasses. Most Uvex products are made in the U.S.
Clip on side shields- These are shields that attach to the sides of glasses that do not have side protection. Most clip on side shields do not make the prescription glass Osha compliant. The lens itself must be a polycarbonate impact resistant lens in order to pass.
Chemical Splash Goggles- Goggles that provide a tighter fit than safety glasses for maximum protection .from chemicals, acids, or paint.
Ultra-Violet radiation is divided into UVB radiation (290-315 nm) shorter wave lengths and UVA radiation (315-380 nm) longer wave lengths.
Here are a few facts about UV radiation.
• UV causes photo keratitis conjunctivitis commonly known as snow blindness
• UV contributes to and accelerates the development of cataracts
• UV causes corneal degeneration and contributes to the development of pinquecula and pterygium
• UV causes degeneration of retinal pigment epithelium (this accelerates "age related macular degeneration"- ARMD) which is a major cause of blindness in North America today
• UV causes tumors of the eyelid. These squamous cell carcinomas are common and serious. A malignant melanoma will be fatal in most cases.
You should understand that eye tissue does not develop a tolerance to UV radiation. Protection from UV radiation (both UVA and UVB) is important, especially with our depleted ozone layer. No one is immune to its ocular effects. People with blonde hair and blue iris' are most vulnerable to UV damage. Damage to eye tissue by repeated exposure to UV radiation is incremental and irreversible. Some medications can increase your sensitivity to UV radiation. Some examples of these medications are tranquilizers, anti-hypertensive, diuretics, oral contraceptives, antipsychotics, antidiabetics, and antibiotics. With this background information you can now appreciate the value of UV inhibitors in spectacle lenses.
Spectacle lenses are commonly made from 3 materials: Crown Glass, CR Resin, and Polycarbonate. In terms of the best safety, polycarbonate lenses rank at the top followed by CR39 resins and then a treated crown glass lens. The polycarbonate and CR39 resins lenses can have a scratch resistant coating applied and they are about half the weight of crown glass lenses. When comparing polycarbonate lenses to lens materials made from crown glass, it is interesting to note that clear and coated crown glass lenses provide no effective protection from UV radiation. Some solid (through the glass) tints offer partial UV radiation protection. CR39 resin lenses block UVB and therefore offer partial protection in their clear form. (A UV inhibitor can be added to block UVA in the CR39 material). Polycarbonate lenses block UVA and UVB (up to 380 nm) in the clear form.
SOURCES OF UV LIGHT
• Low Pressure mercury lamps, such as fluorescence or "black lights"
• Low pressure mercury lamps, such as actinic lamps
• Low pressure mercury lamps, such as germicidal lamps
• Medium pressure lamps, such as photochemical lamps
• High pressure mercury lamps and metal halide lamps, such as sun lamps
• High and very high pressure mercury and xenon lamps such as sun lamps, solaria, pulsed lamp systems
UV LIGHT AND THE EYE
In addition to visible light, the sun also radiates energy at higher and lower wavelengths, just as sounds can be too high, or low-pitched to hear. We can feel lower-energy radiation on our skin as heat. That's infrared (IR), beyond the red end of the color spectrum. Too much infrared can be harmful, but hazardous infrared light are not as common as other, high energy end of the spectrum, called ultra-violet. UV means "beyond blue".
Intense ultra-violet sources are common, like sunlight, tanning beds and welding arcs. But fluorescent lights and computer screens are not significant sources of ultra-violet light. There are three sites in the eye where UV often causes damage. At the cornea, sudden intense UV exposure can cause a "flash burn". This makes the cornea and iris sore for a day or two, such as a sunburn on the skin. A sore iris can be very painful in bright light. With enough exposure, the cornea turns hazy white, sometimes beyond its ability to heal. This is the mechanism of snow blindness. Slower, more chronic UV exposure is thought to promote a condition where membranes around the cornea grow too aggressively-pinguecula and pterygium.
The retina (the inner lining that perceives light) is very sensitive to ultra-violet. It develops defects, holes and blisters when exposed to substantial UV. Retinal problems after cataract surgery were diminished substantially when the FDA approved UV coatings on lens implants. Finally, the crystalline lens inside the eye can be demonstrated to change in response to ultra-violet, and any loss of transparency is technically a cataract. But the typical cataract has adaptive (beneficial) aspects, namely the side effect of protecting the sensitive retina. The lens turns yellow (the best color to block UV) and gets milky, measurable more opaque to ultra-violet. However, farmers and bookkeepers don't differ enormously in their incidence of cataracts.
There are situations where UV absorbing lenses are a good idea. If you spend a lot of time in sunlight, or on water, sand, snow, or around arc welders, you would likely benefit from UV protection.