Through a different lens

Consider tint, impact resistance when choosing the right safety lenses

Wade Harding stood holding a plank of wood steady as a co-worker shot spikes with an air nailing gun into the wood. Suddenly, a spike ricocheted off the wood and flew towards his left eye. When the 9-cm spike lodged in the lens of his safety glasses, the ironworker in Vanderhoof, B.C., fell backwards and felt the nail graze his eyelid. Later that day, after a visit to a hospital, Harding returned and finished his shift.

Safety glasses are essential to protecting workers’ eyes. Ocular injuries can lead to irritation, infection, burns and temporary or permanent vision loss.

Knowing how to select the right lenses for a company’s glasses can be a complicated task. It starts with checking federal and provincial OHS laws that set out specific requirements for personal protective equipment. Most jurisdictions in Canada require use of eyewear certified by the CSA Group. All eyewear that meets or exceeds CSA Z94.3, Eye and Face Protectors, is stamped with the association’s mark.

The next step is a hazard assessment. Most eye injuries are caused by flying particles and chemicals. They may also be caused by objects, such as a tree branch or chain, swinging from a fixed position. 

In addition to looking for potential hazards, managers should consider the nature of the job, says Dave Shanahan, OHS standards project manager for the CSA, based in Toronto. There may be a need for visual acuity, or other special requirements. Truck drivers, for example, have to be able to distinguish certain colours in difficult conditions, such as warning lights.

The work environment should also be assessed, says Shanahan.

“They should look at whether or not the environment is very harsh and dusty, whether or not it’s very humid or dry, whether the person will be working in direct sunlight or be working under fluorescent lights. All these environmental factors need to be taken into account,” he says.

Managers must also identify individual workers’ needs. Some will require prescription glasses; others will have such eye health conditions as light sensitivity and colour blindness.

Impact resistance

The primary quality of safety lenses is impact resistance. Material, thickness and dimensions all play a role in allowing the lens to withstand certain impacts without shattering or failing.

The most common type of material used for lenses today is a thermoplastic polymer called polycarbonate. It is extremely impact resistant and is lightweight and heat resistant. Another material that meets the CSA standard is CR-39, a plastic polymer that has high abrasion resistance, is about one-half the weight of glass and provides more choices for coatings and tinting. Lenses made of Trivex, a brand name of PPG Industries, based in Pittsburgh, Penn., are thin and lightweight but often more expensive than those made of polycarbonate. 

Safety lenses are made in a variety of tints or shades. In some lighting conditions, tinted lenses will improve workers’ ability to see fine details. In other cases, workers prefer darkened lenses because they have a specific condition, such as light sensitivity. 

“So, they wish to reduce the light in their environment in order to not have to squint or see a halo effect (a ring or streak around a light),” Shanahan says.

However, he cautions, when tinted or shaded lenses are selected, the employer should ensure they are CSA-compliant. Some types of tinting and shading can affect the impact resistance of the lenses.

Photochromic, or transition, lenses are light-sensitive, changing their tinting as light intensifies or weakens. Polarized lenses help eliminate glare from the sun and maintain visual acuity. Clear, tinted, polarized and photochromic lenses offer various degrees of protection against ultraviolet light. Tinted lenses do not always have UV radiation protection built in.

Workers who spend a great deal of time outdoors and in bright sunlight — such as oil rig workers and some public sector employees — should wear safety sunglasses.

Welders, too, who can suffer severe eye damage by exposure to the UV light caused by arc flash, need tinted lenses. Getting the right tint for this kind of work is more involved, says Charlotte Kessler, vice-president of business development at Regina-based F.O. Safety Eyewear.

“There’s a wide array of UV tints, different colours based on the different wave lengths they’re looking to block,” she says, adding there are few choices available in prescription.

“With prescription, the tint process is different, so it’s a lot harder to do. You can do outdoor tints and some basic colours. You just wouldn’t be able to do infrared tints, that sort of thing.”

Use of tinted glasses depends on several factors, Kessler says. It is often policy-driven: some companies prohibit tints in certain areas. Where workers are going in and out of a site frequently, managers may choose transition glasses, so employees are not changing back and forth.

Other companies find the colour doesn’t change fast enough, creating a potential hazard. In these cases, they may opt to provide employees with two pairs of glasses: one clear, the other permanently tinted.

Providing two pairs is the better option, Kessler says. Employees then have the protection they need in
both situations.

“You choose tint for outdoor work. And when they’re outdoors, they can have a true polarized lens to block the glare. The glare, when you’re on a construction or mine site, for instance, is often more of a factor than the sun, especially in the winter,” she says.

Digital lenses allow for better optics and give employees the best chance of being able to see “anything that may be coming at them,” says Kessler.

“We can be so much more precise in how we lay the prescription out through the lens that we can widen the visual range of the (worker),” she says.

Safety lenses are often coated to preserve their effectiveness against factors that impair visibility.

An anti-scratch coating protects against scratches that can happen when glasses are carried in a worker’s pocket, left on a workbench or exposed to abrasive elements. And an anti-fog coating can protect against condensation forming on the lens. 

In selecting safety lenses, Shanahan says, managers should always remember one size does not fit all. Glasses bought in bulk are unlikely to address the requirements of the workplace environment or of workers’ needs, proving less effective and uncomfortable for some people.

“Meeting individual needs can enable the worker to do his or her job better,” he explains. “And there may also be a comfort factor. So, a person may be straining their eyes to see or the glasses feel physically uncomfortable on the head. That’s a disincentive for wearing them.”

 Style, too, can encourage workers to wear safety eyewear, Shanahan says. Workers often used to complain protective eyewear looked boxy and rigid and was bulky in size. But manufacturers now are producing glasses that are both effective and attractive.

 “They’re getting a lot more space-age looking — wrap-around varieties. That might be an incentive for some people to wear eyewear. It makes them look good as well as protects them,” he says. “After all, you can specify the best personal protective equipment. But if it’s not worn properly, or when it’s really needed, then it defeats the whole purpose.”

Linda Johnson is a freelance writer based in Toronto. She can be reached at [email protected].