Laser use at the University of Michigan (UM) encompasses many disciplines and applications. Due to the wide array of lasers and the potential hazards unique to each, OSEH has developed Laser Safety Guidance documents which address work practices to be followed while working with lasers at the UM. These guidelines should be used as tools for laser users when developing a laser safety program. This program must be designed to protect all employees from potential hazards and meet federal, state and industry standards.
Class 3b & 4
The unprotected human eye is extremely sensitive to laser radiation and can be permanently damaged from direct or reflected beams. Maximal care should be taken to provide protection to all persons working with high powered lasers by providing protective eyewear, as well as adequate engineering and administrative controls. For further information, refer to OSEH's Laser Safety Guideline.
What are the Effects of Laser Energy on the Eye?
The site of damage depends on the wavelength of the incident or reflected laser beam:
- Laser light in the visible to near infrared spectrum (i.e., 400 - 1400 nm) can cause damage to the retina resulting in scotoma (blind spot in the fovea). This wave band is also known as the "retinal hazard region".
- Laser light in the ultraviolet (290 - 400 nm) or far infrared (1400 - 10,600 nm) spectrum can cause damage to the cornea and/or to the lens.
Are There Any Specific Symptoms of Laser Eye Injuries?
The extent of ocular damage is determined by the laser irradiance, exposure duration, and beam size:
- Exposure to the invisible carbon dioxide laser beam (10,600 nm) can be detected by a burning pain at the site of exposure on the cornea or sclera.
- Exposure to a visible laser beam can be detected by a bright color flash of the emitted wavelength and an after-image of its complementary color (e.g., a green 532 nm laser light would produce a green flash followed by a red after-image). When the retina is affected, there may be difficulty in detecting blue or green colors secondary to cone damage, and pigmentation of the retina may be detected.
- Exposure to the Q-switched Nd:YAG laser beam (1064 nm) is especially hazardous and may initially go undetected because the beam is invisible and the retina lacks pain sensory nerves. In other cases, damage may be associated with an audible "pop" at the time of exposure.
Personal Protective Eyewear
Protective eyewear in the form of goggles, glasses, and shields provides the principal means to ensure against ocular injury, and must be worn at all times during laser operation, especially during alignment procedures. Laser safety eyewear is designed to reduce the amount of incident light of specific wavelength(s) to safe levels, while transmitting sufficient light for good vision. Each laser requires a specific type of protective eyewear, and factors that must be considered when selecting eyewear include: laser wavelength and peak irradiance, optical density (OD), visual transmittance, field of view, effects on color vision, absence of irreversible bleaching of the filter, comfort, and impact resistance. Ignorance of any of these factors may result in serious eye injury.
Where to go in the Event of an Injury
Call Occupational Health Services 764-8021 during regular business hours. After hours, go to the University of Michigan Health System's emergency department.
In accordance with ANSI Z136.1-2014 an area which contains a Class 2 or Class 2M laser or laser system should be posted with an appropriate caution sign. (See example below)
In accordance with ANSI Z136.1-2014 an area which contains a Class 3R, Class 3B, or Class 4 laser or laser system shall be posted with an appropriate danger sign. (See example below)
Warning sign for temporary controlled areas. (See example below)
A limited quantity of Class 3R, 3B, and 4 signs are available through OSEH. For more information on laser signs and/or requirements contact Russ Garcia at OSEH, (734)647-5224.