Lasers in the visible and near infrared range of the spectrum have the greatest potential for retinal injury, as the cornea and the lens are transparent to those wavelengths and the lens can focus the laser energy onto the retina.
The risk of eye injury from laser light and heat is particularly of concern as eyes focus and intensify light entering them. Repeated exposure to relatively low powered lasers, or from a single exposure to medium powered lasers may cause long term damage to sight or minor damage to skin.
Class 4-High Power Lasers and Laser Systems (top)
A high power laser or laser system that can produce a hazard not only from direct or specular reflections, but also from a diffuse reflection. In addition, such lasers may produce fire and skin hazards.
The human body is vulnerable to the output of certain lasers, and under certain circumstances, exposure can result in damage to the eye and skin.
The major danger of laser light is hazards from beams entering the eye. The eye is the organ most sensitive to light. Just as a magnifying glass can be used to focus the sun and burn wood, the lens in the human eye focuses the laser beam into a tiny spot than can burn the retina.
For visible-beam consumer lasers, there are four main classes. Each is described in more detail here: Class 2, Class 3R, Class 3B and Class 4. The first two Classes are relatively safe for eye exposure; the last two are hazardous. The chart below shows how the eye injury hazard increases as the laser's power increases.
Thermal effects are the predominant cause of laser radiation injury, but photo-chemical effects can also be of concern for specific wavelengths of laser radiation. Even moderately powered lasers can cause injury to the eye. High power lasers can also burn the skin.
With high power lasers, the damage can occur in less time than a quarter of a second. Symptoms of a laser burn in the eye include a headache shortly after exposure, excessive watering of the eyes, and sudden appearance of floaters in your vision.
In the U.S., it is legal under federal law to own a laser of any power. But often people talk about “illegal laser pointers”. This is somewhat confusing shorthand meaning that the manufacturer or seller illegally called a laser above 5 milliwatts a “pointer”, or illegally promoted it for pointing purposes.
CLASS IV LASERS: Class IV lasers are systems with power levels greater than 500 mW for continuous wave lasers or greater than 10 J/cm for a 0.25 s pulsed laser. These lasers will produce eye, skin and fire hazards. This includes intrabeam viewing, specular reflections or diffuse reflections.
Ablative lasers are best for individuals with significant skin damage or aging concerns who are looking for substantial improvements. However, because they are more aggressive, they come with longer recovery times and a higher risk of side effects like redness, swelling, and scarring.
One of the most common tell-tale signs of too much laser is super-sensitive, red skin. If you overdo lasering, your skin might not get the time to recover and become more sensitive, leading to other broader issues such as pigmentation.
Skin injuries can be caused by powerful lasers at any wavelength. Focused beams can evaporate tissue and result in third degree burns. In the UV region (< 400 nm) even low level exposures from scattered radiation can cause erythema (sunburn), skin cancer, or accelerated skin aging.
For visible-light lasers, Class 4 lasers' have an output power 500 milliwatts and above. There is no upper limit for Class 4 -- this is the most hazardous laser classification.
These include both direct beam hazards such as tissue burns, eye damage, endotracheal tube fire, drape fire, and explosion of gases, or non-beam hazards (those that are secondary to the actual beam interaction) such as laser generated airborne contaminants (surgical plume), electrical damage, toxic dyes, and system ...
The most common accident scenarios involve: performing alignment while not wearing proper eye protection, stray beams reflected off optics; jewelry, badges, or other objects inserted or falling into the beam path; poor communication between users, wearing the wrong eyewear for wavelengths being used; inadequate or no ...
At 150 milliwatts, the beam from a laser can be felt on the skin, depending on the beam focus, and at roughly 500 milliwatts, the laser's beam can be a skin burn hazard if the person is within a few meters of the laser.
Electrical hazards
Many lasers use high voltage and high current electrical power. The danger of electrical shock or electrocution arises when an untrained or unauthorized person tries to perform maintenance work without following the proper safety procedures. ANSI Standard Z136.
Even though the beam coming out of a laser level has only a small amount of power, it is concentrated enough to harm your eyes. Anyone using a laser level should follow the below precautions: NEVER stare into a laser beam.
Some lasers emit radiation in the form of light. Others emit radiation that is invisible to the eye, such as ultraviolet or infrared radiation. In general, laser radiation is not in itself harmful, and behaves much like ordinary light in its interaction with the body.
The health effects that could occur due to exposure to a laser beam are damage to the skin and eyes. Skin effects include erythema, elastosis (photoageing), immediate pigment darkening (tanning), burns and skin cancer. Eye effects include photokeratitis, photoconjunctivitis, cataracts, photoretinal damage and burns.
Class 2 visible-light lasers are considered safe for unintentional eye exposure, because a person will normally turn away or blink to avoid the bright light.
If used incorrectly they can cause ocular damage, potentially resulting in devastating vision loss. The ocular and visual morbidity can result in significant expenses for medical care and inability to work (temporarily or permanently) for civilians and military personnel.