Laser pointers are visible lasers with a relatively low power output which are frequently used in lecture halls and demonstrations to point at topics of interest on a presentation board. In a school setting, they have become ubiquitous, and they are very useful teaching aids. A drop in the price of laser pointers has also led to increased use among the general population. More common use of these devices has raised concerns about their safety, especially around the eyes.
The biggest concern with laser pointers and the eyes is temporary optical problems. These issues include flash blindness, glare, and afterimages. Flash blindness occurs whenever someone is exposed to a bright light source. While it only lasts for a few seconds, it can be extremely dangerous when someone is involved in a task which requires vision, such as driving. Afterimages can last for several days, and take the form of small spots in the vision. Glare, a reduction of visibility caused by bright light, occurs while the laser is directed at the eyes.
Fortunately, the eye problems most commonly associated with laser pointers do not take the form of permanent damage. Reduction of visibility can certainly represent a danger, however, and these devices should be used with care for this reason. More profound optical damage can also result, if the exposure is prolonged. Most laser pointers have a very low power output, but when it is focused on the retina through the lens of the eye, it can cause damage. Continuously staring into a laser through a fully dilated eye for over one minute may cause a retinal burn.
In most regions, the labeling of laser pointers is regulated. The device should have a “caution” label which also indicates which class the laser is in, and the power output. Many laser pointers are IIIA devices, meaning that there is a potential for damage with direct exposure to the laser. Class two lasers are less powerful, and are a better choice if you are concerned about safety. However, the lower light output may not be effective in a lecture hall.
If used responsibly, a laser pointer should not present a danger. It should never be used as a toy or pointed directly at someone else. When using a laser pointer outdoors, be aware of passing cars and aircraft, as there have been documented instances of issues related to lasers in the eyes of pilots and drivers. Do not let a child use this device, and if you find one pointed at your eye, move and remind the person pointing it at you that these devices should not be directed toward someone's face.