More than 1,000 eye injuries occur in the workplace daily. About 60% of these injuries happen to people who are not wearing any protective eyewear. About 4% happen because people are wearing the wrong type of safety products. This section looks at the reasons why people need to protect themselves from eye injury on the job or at home. It reviews types of safety eyewear and lenses, standards for safety products, and how to care for safety lenses.
Why wear safety glasses?
According to the U.S. Bureau of Labor Statistics, about 1,000 eye injuries occur in the workplace daily. Flying debris accounts for about 70% of occupational eye injuries, while chemical splashes are responsible for about 20%. In about 60% of accidents, the worker was not wearing safety eyewear. In about 4%, the worker was wearing the wrong type of eye protection.
Many employers are required by law to pay for safety eyewear for their employees. But it’s up to each worker to learn how to wear and use safety eyewear appropriately to prevent permanent eye injury.
In any environment where workers are exposed to flying particles, chemicals, vapors, splashes, dust, metal shavings, fiberglass or glass, heat, or intense light, experts warn that prescription glasses and contact lenses are not enough to prevent eye injuries.
Factories and laboratories are not the only places where people are vulnerable to work-related eye injuries. In the USA alone, nearly 110,000 people suffer eye injuries every year in home accidents with household cleaners, flying debris in home workshops, and tree or shrub branches during yard work.
When handling power tools, lawn or gardening equipment, and hazardous chemicals, experts strongly recommend the use of safety goggles. Protective eyewear should fit snugly and properly, they say. Safety glasses or goggles should give workers clear, distortion-free vision. The straps, frames and lenses should be durable yet fit comfortably.
Your eye doctor (optometrist or ophthalmologist) can advise you about the appropriate choice of protective eyewear for your occupation.
Several countries have set standards to ensure the impact resistance of safety eyewear in the workplace.
In the United States, the Food and Drug Administration (FDA) requires that all eyeglass lenses meet the minimum requirement for impact resistance in a drop-ball test. All lenses must withstand the impact of a steel ball dropped from a height of 50 inches.
Voluntary standards for eyewear safety are set by the American National Standards Association (ANSI). These standards were developed with the American Optometry Association (AOA), American Optical Industry Association (AOIA), Optical Manufacturers Association (OMA), American Academy of Ophthalmology, Optical Laboratories Association (OLA), Opticians Association of America (OAA) and others.
ANSI standard Z87.1 sets minimum performance guidelines for occupational eyewear to protect workers from job-related eye injuries. Occupational eyewear that meets ANSI standards may bear a "Z87.1" marking.
Many U.S. states have laws that require workers in certain occupations to wear safety eyewear. In some cases, employers must supply protective eye equipment for their employees.
In Europe, tests for impact resistance differ from North America. In the static load tests, a 23-lb. weight is placed on the lens. If it can deflect the weight for 10 seconds without shattering, the lens is considered safe.
Wherever the job, experts advise employees to check with their eye doctor to find out more about standards for safety eyewear.
Safety glasses
Industrial-strength safety glasses protect the wearer from flying particles and, to some degree, from hazardous chemicals. For extra protection, shields may be attached to both sides of the frame. In the USA, side shields must be attached before safety glasses can receive American National Standards Institute (ANSI Z87.1) approval. Experts advise anyone who does machine tooling, woodworking or grinding to wear side shields.
Safety glasses use specially polycarbonate, plastic or treated glass lenses, which are designed to meet industrial standards. According to experts, safety frames should hold lenses in place during a heavy impact. There is less risk that polycarbonate lenses of more than 2 mm thick will fall out of safety frames, they say.
Safety goggles
From nose to ear, safety goggles provide complete front and side protection from airborne debris. These goggles can be worn over prescription glasses. Because they seal against the face, safety goggles usually offer better eye protection against flying particles and chemical splashes. Experts recommend safety goggles when gardening, working with glass, pouring small quantities of chemicals from manual devices, handling blood or other potentially infectious liquids, repairing cars or trucks, grinding or chipping, cutting brush or lumber, and mowing lawns.
Face shields
Face shields protect the face from corrosive chemicals, blood or potentially infectious liquids, flying chips and other airborne debris. They are not designed to protect the eye from a heavy impact. They are primarily used by people who work in laboratories or handle light chemicals. Face shields should not be worn as primary eye protection. Because these products do not seal against the face, experts advise workers to wear safety goggles under face shields.
Welding goggles, shields and helmets
Welding goggles and shields protect the eyes against intense light and hot flying sparks. Since welding generates infrared light, these products also contain an infrared-absorbing filter. Generally, the degree of protection is rated on a scale. The higher the shade number, the greater the protection against infrared light. Different types of work demand different degrees of protection, so experts advise workers to check what shade factor is required for their job. Color or tint alone is no guarantee of protection against infrared exposure.
Task-specific eyewear
Some manufacturers produce safety eyewear for employees who need eye protection during specific tasks, such as working with lasers or radiation.
The choice of lens type is an important safety consideration, advise experts. The U.S. Consumer Product Safety Commission estimates that 2,417 eye injuries were related to eye-protection devices in 1995 (the latest year for which statistics are available). And, according to U.S. Bureau of Labor Statistics, about 4% of eye injuries that occur on the job each day are caused by the inappropriate choice of safety eyewear.
Glass, plastic or polycarbonate lenses are used in safety eyewear. All have certain advantages and disadvantages, experts state. Most lenses are available with lens treatments, including tinted, abrasion-resistant, ultraviolet and anti-reflective coatings.
Glass has the best optical properties (Abbe value: 60) but most weight and least safety protection. Glass lenses have little haze and are highly scratch-resistant, but they shatter easily and react with fluorides. Glass lenses are not recommended for safety protection, except in extremely abrasive environments.
Plastic lenses are about half the weight of glass. The optical properties of plastic (Abbe value: 58) are close to those of glass. Plastic lenses are inert to chemicals and generally safer than glass.
Polycarbonate is the lens material of choice for safety protection. It is stronger than comparable lenses of glass or plastic. However, polycarbonate has worse optical properties (Abbe value: 30). This material is most vulnerable around the periphery, where it may crack or split under pressure. Polycarbonate scratches more easily than glass or plastic.
Only polycarbonate is tough enough.
A Tufts University study, published in the American Medical Association Journal, found that only polycarbonate lenses were strong enough to withstand impact tests with golf balls, tennis balls and air-gun pellets. Even thick, plastic safety glasses did not provide enough eye protection from these hazards.
The study tested four industrial safety-eyewear lenses that met U.S. ANSI standards. Objects were fired at lenses at speeds that reflected a range of potential impacts in industry, the military, hobbies, car crashes and more.
Plastic lenses shattered under the impact of a tennis ball fired at 55 miles per hour (mph). High-index plastic lenses faired worse, shattering at just 40 mph. Surprisingly, glass lenses shattered at 89 mph.
Only polycarbonate lenses exceeded impact test parameters. When a baseball was fired at the highest possible velocity (135 mph), 3.1-mm thick polycarbonate lenses remained intact.
Lens care
Cracked, pitted, fogged or scratched lenses must be replaced immediately, warn experts. These lens faults reduce clear vision and compromise impact protection. Experts advise workers and hobbyists to inspect safety lenses frequently and immediately replace any worn, broken or damaged parts.
Experts suggest that workers clean safety lenses often in mild soap and lukewarm water. A microfiber cloth can clear grease and dirt from safety lenses without danger of scratching. Experts advise against the use of solvents and paper products, which can scratch or damage lenses.
To sterilize and disinfect safety lenses, experts suggest gas or ultraviolet sterilization. Alternatively, the lenses can be immersed for 10 minutes in a generic liquid disinfectant that won’t harm plastic or polycarbonate materials. Allow the lenses to air dry, as rinsing stops the disinfection process. Special disinfectant sprays can be purchased from safety eyewear manufacturers.
Source
American Medical Association Journal. 1997; v. 277, no. 2: p. 142-144
