The use of laser pointers
has become fairly widespread. The pointers are useful tools
for educators in the classroom and for lecturers at
conventions and meetings.
However, due to the low cost and
plentiful supply, these pointers are now being purchased and
used by the general public, including children, and used in
a way not intended by the manufacturers.
As a result, serious concerns about the
hazards of laser pointers have surfaced. Adding to the
dilemma and potential harm is the fact that not all laser
pointers are labeled properly. The lack of proper labeling
makes it difficult to discern if you have a pointer that
could create serious damage. One sure way to know if a laser
pointer is potentially dangerous is to test it and see if it
is capable of burning holes in paper, lighting matches or
popping balloons. If it is capable of any of these actions
it is most likely able to harm human eyes.
While the majority of the laser pointers
contain low to moderately powered diode lasers, more
powerful lasers can be found on the market. They are usually
imported from other countries that may have deficient or
non-existent standards for safe operation of lasers. These
pointers can present a significant potential for eye injury
and are often not properly labeled according to FDA
regulations. There are currently no restrictions for
purchasing laser pointers in the USA. However, the FDA has
issued a warning for laser pointers, urging that they be
used as intended, not as toys, and not by children unless
under adult supervision. As usual, this ethical standard
will eventually turn into a law if the public does not abide
by the recommendation.
The FDA warning has stated specifically
that exposure for 10 seconds or longer endangers the human
retina. In May, 2005, ophthalmologists at the Mayo Clinic
reported that green laser light will damage pigment cells in
the retina with as little as 60 seconds of exposure.
The misuse of lasers takes many forms.
They are sometimes used to annoy, distract and even
intimidate other people. Lasers are being flashed at
athletes during games to impair their performance and at
movie screens in theaters as a general distraction. They are
used to mimic a gun's laser sight. A red beam is often
projected to aim high powered weapons at their targets. This
particular action has caused alarm in police departments and
communities across the country. For example, police officers
have reportedly drawn their weapons when the light from
laser pointers is mistaken for a gun sight. Laser beams
projected into airspace to intercept aircraft have caused
distractions and temporary vision impairment to pilots. Most
of these incidents are considered malicious and demonstrate
a lack of understanding of the potential consequences of
laser illumination. Unfortunately, as the availability of
these devices has increased, so have the reports of their
misuse.
Momentary exposure from a laser pointer
can cause discomfort and temporary visual impairment, such
as glare, flash blindness and afterimages. The symptoms may
last only for a few seconds or minutes but can be extremely
dangerous if the exposed person is engaged in a vision
critical activity, such as driving a car or flying an
aircraft. The light energy that some laser pointers can
deliver into the eye may be more damaging than staring
directly into the sun. For example, a 15 year old Swiss boy
attempted to create his own laser light show using a laser
pointer which he bought on the internet together with a
mirror. Instead he inadvertently beamed the laser into his
eyes, creating permanent damage to his vision.
Dr. Martin Schmid, head of the retina
unit in the Department of Ophthalmology at Lucerne Cantonal
Hospital in Switzerland, is one of the authors of the case
report detailing the young boy’s eye damage in the New
England Journal of Medicine. The teenager noticed
immediately that his vision was blurry but was fearful of
informing his parents of the incident. Two weeks later he
couldn't hide the problem any longer and sought the help of
a doctor. The vision in his left eye was only fingers at
three feet. The right eye also showed severe acuity loss.
Dr. Schmid reported that the boy could barely see newspaper
print. A hemorrhage was noted in the right eye and several
retinal lesions in the left eye. After four months his
vision showed some improvement but remained moderately
impaired. The doctor concluded that laser pointers are a
"legitimate public menace."
The laser pointer used by the young Swiss
victim produced an output of 150 milliwatts, which is far
above the maximum output of 5 mw that is expected from a
laser pointer that is sold to the public. It is worth noting
that it's possible to purchase laser pointers as strong as
700 mw, and such a device may not look any different than a
lower powered laser. Dr. Schmid adds that there are
instructions on the internet for changing low powered
devices into high powered ones. Eye specialists concur,
"Children shouldn't have access to laser pointers. They
are not giving presentations, so why would they need to have
them?" Dr. Roy Chuck, chair of Ophthalmology and Visual
Sciences at Montefiore Medical Center and Albert Einstein
College of Medicine, New York City, states, “When it comes
to laser toys buying a well known name brand may be helpful
in this case. But when you're buying off the internet, it's
not as regulated and you just can't tell what the strength
of the laser may be."
Lasers used in toys are labeled as Class
I, but the products aren't always labeled properly. It is
stressed that even at a safe level, if the child stares into
the beam long enough it can cause eye damage. One may
purchase a "safe" laser toy, but it's possible
that a creative child may turn to the internet and figure
ways to boost the power of the laser. Listed under
"burning laser pointers" there are a huge amount
of videos showing dangerous experiments that can be done
with the lasers. Moreover, there are an increasing number of
home pages and videos that demonstrate how to turn legal,
low power lasers into burning, high power lasers.
There have been reports of more powerful
laser pointers imported from Russia and China that lack the
appropriate warning labels. Some of these laser pointers
emit green beams from frequency doubled Nd:Yag lasers
operating at 532 mw and have emissions significantly
exceeding the maximum permissible exposure. One of the
lasers has a filter in the cap, which, if removed, allows
the laser to emit both 532 mw and 1064 mw beams. This places
the laser in excess of 15 mw making it an even more
hazardous Class III B laser as opposed to the currently
allowed class III A laser. All laser pointers should have a
small sticker on them with either a yellow
"caution" or a black and red "danger”
designation. The experts say that it would be prudent not to
purchase or use unlabeled laser pointers. Why should we be
worried about a lowly 5 mw laser that is 5 thousandth of a
watt which is less than one percent of one percent of the
power of a 60 watt incandescent bulb? First, the numbers are
used differently.
Light bulb wattage measures the power it
uses. It only converts about 10 percent of that electrical
power into light. In a laser, the power is a measure of the
light output. Second, the light bulb gives light in all
directions, so you only see a small part of the whole at any
one time. As you move away from the bulb, you see a quarter
of the light every time the distance is doubled. A laser
pointer gives all the light energy in one small,
concentrated beam. If it gets into the eye, you receive all
of the laser's energy, not just a fraction of the energy as
in the ordinary light bulb. Third, a light bulb gives off
light at many different wave lengths. A laser is
monochromatic; it is only one, concentrated wavelength with
no loss of energy. The resulting light energy is more
potentially damaging as a result.
The acronym Laser stands for Light
Amplification by Stimulated Emission of Radiation. The
common red laser pointer is a diode laser. This is really
just a special type of transistor, or diode that creates the
wavelength used in the pointer. Because of the unique
features of laser light, it is magnified 100,000 times as it
passes through the eye. The light energy not only passes
through to the retina, but the eye focuses the light on the
retina. The combinations of these two features increase the
likelihood of ocular damage through misuse of the laser
pointers.
The eye actually sees a small part of the
electromagnetic spectrum that runs from cosmic ray energies
to long radio waves. We see only the wavelengths from violet
to red. Infrared and ultraviolet are just outside our
ability to see. The eye is most sensitive to yellow light
(550nm). Meaning we will see the color yellow faster than
any other color. That is why so many hazard devices (fire
trucks, fire hydrants, etc.) are converting to yellow. At
the same power, 670 nm red light is only 3 percent as bright
as the equivalent in yellow. When determining safety limits
for the laser pointer values must be chosen. As with most
safety boundaries, the limits on lasers have been chosen to
err on the side of caution. Misuse of the lasers or altering
the laser is simply foolish and can have life altering
consequences as with that 15 year old Swiss boy. In life
many factors contribute to something becoming harmful. And
so it is with laser pointers -- different conditions
determine when retinal damage will actually occur.
