Lens coatings for enhanced safety eyewear performance

By Glyn Jones

Advances in technology have significantly improved the performance of safety eyewear, from frame and lens materials to advanced lens coatings. Innovations from research and development efforts have allowed leading manufacturers to develop a range of lens coatings and treatments to optimize performance. A lens coating is a thin layer applied to safety eyewear lenses to enhance the wearer’s vision or overall field performance. These coatings can be used on both regular and prescription safety eyewear, often in multiple layers to offer further benefit. The diverse range of options makes it easier to take advantage of the current trends for improved performance.

Types of Lens Coatings

Let’s review eight types of lens coatings and treatments that enhance safety eyewear performance.

Scratch resistance: Most safety glasses are made from plastic polymers that meet the CSA standards such as polycarbonate or polyurethane. While lightweight and shatter-resistant materials these materials are softer and prone to scratching. To mitigate this, a thin coating of a harder material is applied to the surface of the lens. The layer is invisible but produces a lens surface that is less susceptible to scratches, extending its useful life.

Anti-fog: Anti-fog lens coatings help maintain uninterrupted visibility and are particularly beneficial for working in hot, humid, physically demanding, and climate-controlled conditions. Newer lens coating technologies can manipulate moisture, using surfactants coated on the lens surface. One such coating causes moisture droplets to flatten out and form a thin film, reducing the scattering of light and allowing workers to see more clearly. These coatings resist fogging longer than traditional anti-fog coatings, even after washing multiple times—up to 25 washings. This coating can also increase the scratch resistance of the lenses.

*As per Alberta OH&S, Alberta organizations must follow CSA Z94.3 – 2015, which does not provide approval for anti-fog coatings. However, as of December 2023, Eyesafe™ has sole approval to provide this coating in Alberta, as we have tested it to meet impact standards.

Anti-glare (anti-reflective coatings): Early advancements in lens coatings and specialized treatments included mirrored lenses.  Mirrored lenses are a type of anti-glare coating. They have a very thin reflective anti-glare, often metallic, coating on the outside of the lens. They can come in a range of colours but are not necessarily the same colour as the lens underneath and do not affect the colour that the wearer sees. The mirrored surface reflects light, which is what gives them their mirrored appearance, and as a result, less light enters your eyes, reducing glare and making things appear a little darker.

Anti-glare or anti-reflection (AR) coatings are also available without mirroring the lenses. These have a very thin layer which is applied to the front and back surfaces of the lenses. AR coatings reduce the brightness of the reflections from the lenses which makes them clearer to look through and less conspicuous than a mirrored lens. These lenses also increase visual acuity in patients with higher prescriptions and are mandatory for those with a significant prescription.

Blue light blockers:

Blue light is part of the visible light spectrum. It is emitted from fluorescent lights, compact fluorescent lightbulbs, and any LED flat-screen such as on computers and smartphones. Your eyes don’t filter out harmful blue light and longer-term exposure can harm the eyes and cause digital eye strain and fatigue. Blue light-blocking coatings can be applied to lenses which may absorb anywhere from 10% to over 90% of the blue light.

Blue light-blocking coatings work either by reflecting some of the blue light or by absorbing some of the blue light. The reflective coatings do not alter the colour of the light coming through the lenses. The absorptive coatings filter the light and can somewhat change the visible colour coming through to the eyes. Both are effective in reducing blue light exposure.

*As per Alberta OH&S, Alberta organizations must follow CSA Z94.3 – 2015, which does not provide approval for blue light-blocking coatings. However, as of December 2023, Eyesafe™ has sole approval to provide this coating in Alberta, as we have tested it to meet impact standards.

UV protection: UV exposure from the sun can damage the corneas and create other long-term eye damage. Excessive tearing, blurry vision, and sensitivity to light are all symptoms of overexposure to the sun. Wearing glasses that reduce UV exposure is important. UV-protective coatings prevent UVA and UVB rays from penetrating the lens, safeguarding the eyes from sun damage.

The level of UV protection is not directly related to lens darkness. Safety eyewear treated with a UV protective coating can offer protection without darkening the lenses if necessary.

Photochromic (Photogray) technology: Photochromic lenses, also known as photograying lenses, have a coating or are infused with molecules that will darken in response to UV rays, eliminating the need to change glasses when going from indoors to outdoors. A popular brand name of this technology is Transitions lenses developed by Corning in the 1960s.

Even on overcast days, the lenses will darken in response to UV rays penetrating the clouds. A wide variety of colours and shades are available for treated lenses depending on requirements and personal preferences. One challenge is that the lens takes a bit of time to adjust, making things very bright when you first go outdoors into the sun and very dark when you first return indoors. It is also important to note that these lenses may not work behind windshields unless a specific type is requested.

While photochromic lenses may not be the best choice for all safety eyewear applications, they offer versatility for variable work settings.

Polarized: Polarized lenses filter out reflected light, reducing glare and eye fatigue, especially from light reflected off water, snow, or ice. Polarized lenses have a special chemical coating applied to them that blocks and filters light passing through the lens to provide clarity in very bright conditions.

 

The range of lens coatings and treatments has grown significantly in the past few years. Choosing the right lens coatings for your safety eyewear involves a careful assessment of workplace hazards and experimentation with different tints, colours, and lens coatings.

Employees need to be supported in the workplace to ensure that safety eyewear is worn whenever workplace hazards are present. Ensuring any product you choose is CSA-approved is essential, and ongoing advocacy for full compliance with safety eyewear use is crucial for worker eye safety.

 

Glyn Jones is a partner at EHS Partnerships Ltd. in Calgary. He is a consulting occupational health and safety professional with 35 years of experience. He is a regular safety conference speaker in Canada, and he provides program design and instructional support to the University of New Brunswick’s OHS certificate and diploma programs.