Maintenance

ANTI-SCRATCH (hard-coated) LENS GENERAL
Lenses are coated with a silicone based permanent hard coating
Coatings will not wash off
Coatings protect against most chemicals and solvents
Coatings provide a high gloss finish
Coated lenses are easily cleaned and sanitized
Coated lenses are not affected by metalization (mirror lens)

PRIMARY PROPERTIES
Permanent coatings show no loss of anti-scratch properties for a minimum of 2 years
Anti-scratch coating DOES NOT affect the optical characteristics of the lens
Anti-scratch coating provides abrasion resistance to pencil hardness of 8H
Anti scratch coatings are completely UNAFFECTED by the following chemicals or solvents-
Low and high molecular weight alcohol
Glycol ethers
Aliphatic and aromatic solvents
Weal alkali/alkaline earth solutions
Mineral acids and EXCEPTION of hydrofluoric acid

CLEANING AND DISINFECTING METHODS
Wipe clear with a dry clean soft cloth
Clean with soap (mild detergent) and water
Pad dry with clean lint free cloth
Disinfect with the following methods: (does not affect coating)
General disinfectant
UV light germicide chamber
Placed at 100 degree C for 1 hour

PRODUCT MATERIALS: POLYCARBONATE GENERAL
Crystal clear and colorless, amorphous engineering thermoplastic notable for its high impact resistance PC was originally developed for aerospace industry for use in windows for airliners, space shuttles and face shields for astronaut helmets.
PC is a very soft material allowing it to absorb energy from an impact and not crack or break. The drawback to this feature is it's tendency to craze or scratch easily. Therefore most lenses are treated with an anti-scratch coating.
PC is exceptionally light weight due to it's low 1.2 specific gravity
PC, although seldom used for frame material, is more impact resistant than nylon

PRIMARY PROPERTIES
Optical characteristics:
Light transmission 88.0 % astm d 1003
Haze 1.0 astm d 1003
Refractive index 1.586 astm d 542
UV stabilized, won't dry out and become brittle after exposure to sunlight
Filters out 99.9% of all harmful UV radiation
Ability to add UV400 absorber to give extra UV protection (for enviroments with high levels of UV radiation)

CHEMICAL RESISTANCE
Acids-concentrated - FAIR
Acids-dilute - GOOD
Alcohols - GOOD
Alkalis - POOR
Aromatic hydrocarbons - POOR
Greases and Oils - GOOD
Halogens - POOR
Ketones - POOR
*Please note that chemical resistance is greatly increased when coated with an anti-scratch coating

PRODUCT MATERIALS: NYLON
GENERAL
Nylons are generally strong, tough, and resilient polymers
Nylons offer good barrier and high fatigue properties
Nylons offer good abrasion resistance
Nylons offer good resistance to oils, greases and solvents
Most common nylons used in spectacle frames is Nylon 6,6

PRIMARY PROPERTIES
Excellent impact resistance, good thermal stability
High abrasion and weathering resistance
Excellent flow properties
Good dielectric properties
Good resistance to a wide range of chemicals
Hypo-allergenic
A characteristic of nylon is that it has a tendency to absorb moisture. This is a characteristic that gives nylon its toughness. Upon initial injection (at manufacture) nylon frames are very hard and brittle. They are then left to cure so that they will absorb moisture from the air and soften. Once cured, they become very impact resistant. The curing or softening period takes 2-3 weeks.

Health and Safety

UV LIGHT
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 photokerato 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 melonoma will be fatal in most cases.
Protection from UV radiation (both UVA and UVB) is important, especially with our depleted ozone layer. You should understand that eye tissue does not develop a tolerance to UV radiation. 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-hypertensives, 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 lenses, polycarbonate ranks and 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.
There is seldom much UV inside a car, that's why photochromic (also known as polarized) lenses don't get very dark in the car.
If you have had cataract surgery, your surgeon can tell you whether or not your implant is UV protected. If not, you should already know that special protection is important.
The best protection comes from UV400 lens, with the UV absorber built into the material so it will not scratch off. Spectacle lenses made of glass are NOT good UV filters.

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