From medical personnel and construction workers to pilots and members of the armed forces, lasers have become a critical part of many jobs. While our own eye reflexes protect us from many low-power visible lasers, such as the scanners at the supermarket, for many professionals the high-powered lasers required to perform their jobs pose a real threat to their vision. In fact, it wasn’t too long ago that Johns Hopkins hospital reported an alarming tread of eye injuries due to popular laser gadgets used by children and teens, calling for warning labels on these items.
What exactly happens if a laser hits an unprotected eye? In worst case scenarios, it can burn the retina or cornea. When light enters the eye, it is focused by the lens on the retina. When the light is too strong or lasts too long, the pigment in the retina absorbs the light, radiating heat. This is essentially what happens when you look at any bright light too long, including the sun. Reflexes cause you to look away, but often you will continue to see a bright spot for a few seconds while the retina is recovering. Unfortunately, laser exposure often leads to permanent retina or cornea damage. How can you best protect yourself and your employees?
Measuring the Danger
The best protection is to prevent the injury. Safety glasses are an affordable and practical precaution. Additionally, they are required by law in some situations. The Occupational Safety and Health Administration (OSHA) classifies lasers, requiring eye protection for classes 3B and 4. What safety glasses are best to use with lasers? Start by understanding four key features of how protection is measured. Assess the risk of your equipment, then compare that with the specifications of safety glasses.
- Wavelength. It’s critical to know the wavelength of the laser you are working with because laser wavelength is directly related to the potential damage. Wavelength is measured in nanometers (nm). Lasers have an aiming beam wavelength and an operating beam wavelength. The operating wavelength is the one that poses the threat. Be aware that multiple wavelength lasers may require customized eyewear with multiple layers. The wavelength of the laser is directly related to its potential for harm. For example, let’s compare laser exposure with the ultraviolet wavelengths from the sun, which measure 315 to 400 nm. Most of the radiation is absorbed by the lens and damage is minimal, often taking years to present in the form of cataracts. Comparatively, near infrared wavelengths measure 760 to 1400 nm and can cause retinal burns. Far infrared wavelengths, measuring over 1400 nm, can result in corneal burns.
- Scattered vs. Direct. The second variable to assess when selecting eyewear is the viewing environment. Greater protection is needed if workers are in a direct viewing situation as opposed to an area of diffused viewing where the radiation from the laser is scattered.
- Laser Power. Know the potential power of the laser to which you are exposed. Is it a continuous wave or pulsed system? Continuous wave systems will be expressed in the form of watts. The energy expended by multi-pulsed systems will be measured in joules, the pulse length in seconds and the repetition rate in Hertz.
- Optical Density (OD). Optical density refers to the amount of radiation allowed to pass through the lens filter. For example, an OD of 2.0 permits 1/100 of the laser light energy to pass through. Wearing safety glasses with a lower OD than needed can result in an injury.
Assessing Specific Needs
While safety is the priority, there are other factors to consider when selecting protective eyewear. Uncomfortable, ill-fitting or eyewear that obstructs the wearers view can reduce productivity and discourage compliance. When selecting glasses for your staff or yourself, think about the following factors too.
- What’s the best material? Consider the best weight, shape and fit for the job. Many glasses are universal in size, but can be adjusted for a custom fit. If you can wear safety glasses with a lower OD, polycarbonate laser glasses are a lightweight, comfortable option. Glass is a better option when higher OD lenses are required, but can be costly. Nanospec or thin-film-coated filters are lighter than glass and provide precise protection for specific wavelengths and OD, making them a more comfortable option for higher risk jobs. Coated lens technology is also a favored choice because it combines both reflective and absorptive properties.
- What about visibility? It’s important for workers to not have their visibility obstructed, for both safety and productivity reasons. You’ll have to balance options like the added protection of solid side shields with reduced visibility. It’s also important to remember that the color of the glasses can reduce visibility. While certain jobs may require a specific color lens, select what is needed. More protection is not always better if visibility is inhibited. Simply put, balance what’s required to perform the task safely. The coated lenses mentioned above are a popular choice because of their superior visibility over glass and polycarbonate.
- Do you have custom needs? Employers must also consider individual needs, in addition to industry standards. Do you have employees that already have glasses and need fitover safety glasses? Do they need safety glasses with bifocal or transition lenses?
Phillips Safety Products has the largest selection of specialized safety eyewear. Whether you need minimal or maximum protection, fitovers, transition lenses or a bifocal design, we have what you need in stock. Talk to one of our experts about your optic needs. Contact us today.