If you’ve ever held a laser pointer and wondered if it was safe to look directly into the light, the short answer is... No! Shining a laser beam directly into your eye can cause permanent damage. Laser pointers are hand-held devices that produce a focused beam of colored light. These pointers are often used by presenters to point to a particular item on a screen during a presentation.
Laser pointers are rated on the amount of light they produce which is measured in milliwatts (mW). The U.S. Food and Drug Administration’s Center for Devices and Radiological Health requires that all laser pointers made in the U.S. must have a label showing the class rating for that device. The lower the number, the “safer” the pointer is considered to be. Most U.S. made laser pointers produce red light that is in the 3 to 5 mW range. This puts them in the Class 3 category.
Laser pointers that produce 5 mW of light can cause permanent damage to the eye. It is tempting to compare the 5 milliwatt laser to the much higher 60 watt light bulb, but that comparison is not appropriate. Light bulbs are rated on the amount of power they use, not on the amount of light they produce. In addition, light bulbs produce light in all directions which diffuses the power of the light entering the eye. The further away from a light bulb you are, the less of the total light output you actually see from that bulb, which is why light bulbs appear brighter when you are closer to them. Laser pointers produce a narrow band of concentrated light. Looking directly into a laser pointer allows the entire output of the laser’s energy into the eye.
Laser pointers that are brighter than those allowed by U.S. regulations are available for sale on the internet. These pointers present serious risks to vision by causing permanent damage to the retina. The retina is the inside lining of the eye that receives light images and transforms them to electrical signals that can be sent to the brain. Damage to the retina can cause blind spots to develop in one part of the eye, or can cause complete blindness in one eye.
The most likely result of looking into a laser light is flashblindness. This is similar to the bright spot that floats in your vision after a camera flash goes off. The spot eventually fades, but this can take several minutes. Another temporary risk is seeing afterimages, which can last from several minutes to several days. Laser pointers can also create glare either by shining directly into the eye or by reflecting of a shiny surface. These may sound like small risks, but the results can be serious if an airplane pilot or driver of a car suddenly becomes blinded by laser light.
Fortunately, the eye has an automatic safeguard to protect against bright light. When you look toward a bright light, the eye automatically blinks. Forcing yourself not to blink while looking at a laser can cause even more damage to the eye. Children should not be allowed to play with laser pointers without close supervision to protect their vision. The light of a laser pointer reflected in a mirror can be as damaging to the eyes as looking directly in to the light. Paintball participants should also be aware of the danger of looking directly into a laser sight on a paintball gun.
Laser pointers are generally safe when used as the manufacturers intended, but they should not be used as toys. Children should learn not to look directly into a laser light just as they learn not to look directly at the sun. Laser pointers should only be purchased if they are clearly labeled with a safety warning and a U.S. classification of 3 or lower.
Sources:
Scientific American
All About Vision
Princeton University