The evaluation of various safety glasses

Monday, November 16th, 2009 at 1:39 pm Post in Eyeglasses

Prevent Blindness America reports that 700,000 cases of eye injuries happen at work every year in the United States, and the figures of eye injuries at home and during sport are 125,000 and 40,000 respectively. It is also estimated that 90% of these injuries can be prevented by proper protective eyewear.

Regular eyeglasses can not be qualified as safety glasses. Both the frames and lenses of safety glasses must meet a higher standard of impact resistance. In U.S. the OSHA (Occupational Safety and Health Administration) is responsible for supervising workplace safety practices and has adopted safety glasses standards established by ANSI (American National Standards Institute). Protective products that are forced to obey these standards include eyeglasses, goggles, face shields, welding helmets and full-face respirators.

ANSI safety eyewear standards include some key features. Safety lenses have two main types: basic impact and high impact. The impact classification can be determined by a “drop ball” test. The one-itch diameter steel ball will be dropped onto the lens from a height of 50 itches. Basic impact tests examine lenses separately and high impact test evaluate the frame and lenses in together. Thinner prescription lenses should withstand the high impact testing. Lenses always have a “+” mark if they have high impact approval. “V” represents a photochromic lens and “S” stands for a lens with special tint.

There are also some tests for frames of safety eyeglasses and goggles. High mass impact test of frames uses a 17.6 ounces steel projectile. Frames that can retain the lens during the test will pass the test. Durability tests of frames include flammability-resistance test, corrosion-resistance test and so on. A “Z87” mark on a frame indicates that the frame has passed a basic impact test and “Z87+” means high impact. Quality prescription safety frames will be equipped with a “Z87-2” mark.

Certain employers should provide high impact protective eyewear to their employees. Those occupations include carpenters, plumbers, pipe fitters, machinists, millwrights and laborers. For independent contractors, it is also important to choose high impact safety eyewear for additional safety.

For home use, you can purchase non-prescription safety glasses from most hardware, building supply and sports goods stores. But prescription eyewear can only be prescribed by eye doctors or opticians. Most of these glasses are made of polycarbonate and you should choose those with “Z87” or “Z87-2” marks for best protection.

Safety glasses with elastic bands that attach to the back of temples are more helpful during sports. These bands can maintain safety glasses more effectively. Hunting, golfing and sport shooting require both acute vision and best eye protection, so that you should choose lenses with a high impact rating. Lenses with amber or yellow tints can enhance contrast during dim conditions. While fishing, lenses with polarized tint can reduce glare and wrap-around frames can protect your eyes against fish hooks. Photochromic lenses are perfect in changing outdoor lighting conditions. During paintball playing, additional head shields are necessary.

Lightweight polycarbonate is the favorable material for safety eyewear lenses. Polycarbonate lenses are also more impact-resistant. While reducing lens reflections, anti-reflective coating may affect the impact resistance of certain lenses. A prior impact resistance test is important before applying AR coating.