The principal danger from lasers is to the eye. The primary region of concern for low power visible lasers is the retina of the eye.
High powered lasers may cause additional damage in the cornea, and in some cases, skin damage through simple heating caused by the concentrated light energy within a small area.
Experts do not expect that lasers will show any long term cumulative effects. The principal cause of danger is through simple heating caused by the light energy being concentrated in a small absorbing spot. The eye is more sensitive to lasers because of its magnifying lens capability.
Low power helium-neon lasers that are used for alignment devices have no skin hazard and the primary concern is exposure to the retina. It is unlikely that eye damage will occur, but to insure safe operation of the laser, do not stare into the beam or its reflections.
Laser pointers have become widely available and are much less expensive. Instead of being solely educational and business tools, they are now marketed as toys. Increasing numbers of incidents of irresponsible use are being reported. A fact sheet on the potential eye safety problems of laser pointers has been prepared:
What type of light is produced?
Laser pointers are small handheld diode lasers powered by AAA or other small batteries. The diode emits light at a wavelength of 670 nm, producing a narrow intense beam of red laser light which can be directed over long distances. The typical laser pointer has a power output of 5 mW or less; by comparison a fluorescent lamp has a power rating of 40W. What makes the laser potentially dangerous to the eye and vision is the fact that its power is concentrated in the very narrow beam. When directed into the eye, the beam forms an image at the retina that may be as bright as the sun.
Like all lasers, laser pointers are given a hazard classification that is defined by the ANSI Z136.1 Standard for Safe Use of Lasers. A laser pointer is a class IIIA (three A) device. This is a device with the potential for eye damage from direct exposure to the beam.
What is the danger from a laser pointer?
Reports in the news media about people being flashed in the eyes by a laser pointer have mentioned temporary blindness as a result of the exposure. As with photo-flashes, a brief exposure to laser light results in bright afterimages that may interfere with vision, particularly in dim lighting or at night. In addition, attempts to move out of the way of the laser beam may place the exposed person in a dangerous position. For example a driver may lose control of his vehicle while trying to avoid being hit by the laser beam.
It is possible that retinal burns could occur with sustained exposure to the laser beam. Calculations show that the theoretical exposure for a clinically detectable retinal injury is reached after a continuous exposure in excess of 100 seconds. However, this requires a fully dilated pupil and deliberately staring into the beam for the entire time. Most of the incidents reported in the media involve brief, flash exposures to the laser. Under these circumstances, there may be visual discomfort and afterimages that interfere with vision, however there should be no permanent retinal injury.
We must emphasize that laser pointers are not toys. Staring into the beam or directing the beam into the eyes can result in eye injury after extended exposure. We note that some police forces have taken the position that deliberately directing a laser beam into a persons eyes is assault, and may warrant a criminal charge of assault with a weapon.
What should I do if I am flashed in the eyes with a laser pointer?
As soon as you are aware of the laser, look away from the laser beam or close your eyes, and move out of its way. If possible, ask the person shining the laser at you to stop immediately. However, the person with the laser may be quite far away from you and it may not be possible to identify him or her, or communicate directly.
If afterimages and visual discomfort persist for more than a few minutes, see your eyecare professional as soon as possible for assessment.
Reference: University of Waterloo, School of Optometry