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The natural
beautiful light of the sun has been used by man for both medical and
aesthetic purpose for millenniums. Spas in Europe have often been
located on lakes or the oceans to maximize the amount of sun rays one
could experience. People have gone to resorts on one side of a lake in
Hungary for centuries to benefit from the curative powers of the
polarized light reflected off the water. We know now that the lack of
sunlight can contribute to Seasonally Adjusted Depression (SAD) and a
deficiency in vitamin D. So we have learned how to use light to treat
these and other conditions.
We have learned a
great deal about light over the last few hundred years and we are still
learning. One early thing we learned is that sunlight consists of all
the different colored light rays that we can see and many that are
invisible. Some of these are widely recognized to be harmful. The
ultraviolet (UV) light from the sun can cause skin cancers. But we have
learned to use it also. For example, UV light is used to treat
psoriasis in people of all ages.
Man has learned to
make light work for him. First it came from fire, sticks, logs, oils
and other flammable substances. Then Thomas Edison invented the
electric light bulb and progress accelerated. In 1960, Thomas Maiman, a
research scientist at Hughes Aircraft, invented the laser, a very unique
form of light. His first laser was built with a ruby and the light was
red. Laser is an acronym for Light Amplification through
Stimulated Emission of Radiation. Yes, light is
radiation but all radiation is not dangerous like nuclear radiation.
For example, television and radio waves are radiation. Cell phone calls
travel via radiation. So radiation can be very safe and useful as well
as very dangerous. Laser development advanced rapidly in the early
1960’s. A year after Maiman published a report on his ruby laser, the
first visible HeliumNeon (HeNe) was operating. In 1962, Holonyak
developed both the light emitting diode and a semiconductor laser called
a laser diode at General Electric. Both originally produced red light
but can now be designed to emit different wavelengths or colors.
Light travels
through space in waves. Like waves of water, the distance between the
beginning and end determine their effect when they hit something. The
distance between the beginning of one wave and that of the next is
called a wavelength. For visible light, this distance is very short. It
is measured in nanometers and a nanometer (nm) is one billionth of a
meter.
Light of different
colors has different wavelengths but all light of one color have about
the same wavelengths. Blue light is approximately 400-495nm. Green runs
from 495-530nm and yellow is from 580-590nm. Red light starts around
610nm and goes to nearly 800nm where it merges into the near infrared
that becomes infrared light. That is the range of light used by man.
Laser light have
two unique features. One, it is monochromatic or one wavelength
(actually a very narrow band of wavelengths but one color). Two, it is
coherent (successive photons travel in well organized paths, one after
the other). Lasers may have three other characteristics- small
divergence (nearly parallel beams), high mean output power (MOP) and
polarity (waves move in the same plane).
Lasers are named
after the material or substance stimulated to produce the light.
Maiman’s ruby laser
produced 694nm red light. The next type of laser stimulated carbon
dioxide and was developed at Bell Labs. At 10,300nm,
its wavelength is invisible. Many applications of lasers have been developed and
refined. In most material processing applications, which include
changing a material be it stone, metal, tissue, etc., something absorbs
the photonic energy of the laser light and converts it to thermal
energy. The “something” is called a chromophore. The resulting heat
accomplishes the desired effect. Ruby laser is absorbed by red or brown
and one of its first uses was to treat bleeding of the retina in
diabetics. Carbon dioxide laser light is absorbed by water until it
vaporizes. As a result, it is used in surgery where tissue needs to be
precisely removed. The first applications included removing nodules
from vocal cords, pre-cancerous lesions from the cervix and brain
tumors. Lasers with different wavelengths and other operating
characteristics have been developed in the last decade.
A very useful
system that is replacing some lasers is called an Intense Pulsed Light
and is just that. A broad spectrum light source, mercury or sodium
vapor lamp, is activated with a very intense (high power, short
duration) pulse of electricity. This generates a pulse of light. This
light hits an optical filter that only lets certain wavelengths pass
through it. As a result, the light that leaves may be close to
monochromatic but it is NOT coherent or polarized. Some of these light
systems may achieve their effect very differently than lasers.
Generally, the effect is thermal but non-ablative. This occurs because
the pulse is so short-lived that it the heat produced upon absorption
vaporizes just a few cells and does it so quickly that heat does not
spread outward to effect surrounding cells.
At the American
Society for Laser Surgery and Medicine meeting in 1981, a general
surgeon presented a paper in which he used a red filter between the
patient and Kodak projector. He directed the light on a tumor that had
a photosensitive drug concentrated in it. The light activated a cascade
of events that killed the cancer cells. This type of work has evolved
into photodynamic therapy wherein a patient takes a drug that
concentrates in the malignant cells. The cells are exposed to a very
specific wavelength of light that is maximally absorbed by the drug (the
chromophore). The resulting reaction kills the cells. Originally used
in esophageal tumors, one drug, ALA PDT, has been approved for one skin
cancer and is being used on others. In addition, it is used on
precancerous lesions and sun damage areas that contain melanin, a brown
color substance that concentrates the drug.
Low Level Laser
Therapy (LLLT) roots go back to the 1960's when Andre Meister in Hungary
conducted experiments to determine if laser radiation was hazardous. He
observed that it actually accelerated wound healing and appeared to make
hair grow faster. Trelles, Pontinen, Tuner and Hode and others in
Europe plus Ohshiro and Calderhead in Japan advanced the early work such
that Low Level Laser Therapy has been used in Europe and Asia for a
variety of applications since the early 1970’s. This is a non-thermal,
non-ablative therapy that accomplishes its effect through
photobiostimulation. Originally, helium-neon or HeNe lasers were used.
These were later replaced with laser diodes that are much smaller and
more robust than HeNe lasers made with glass tubes. Many different
names have been applied to this type of therapy. They include Low Level
Laser Therapy, cold laser, soft laser, etc. Low Intensity Light Therapy
(LILT) is probably the most descriptive term because it includes the use
of light from other sources, including Light Emitting Diodes (LEDs)
which are becoming very common. The US Food and Drug Administration did
not take this area of application seriously until a few years ago. They
designated LEDs as non-significant risk devices which makes attaining
approval to market much easier. However, they basically ignored the
product until they approved the first system in January 2002. That was
an infrared unit for carpal tunnel syndrome. Since then, they have
approved quite a few systems for musculoskeletal treatment and one LED
system for wrinkles and rhytids.
Within the last
twenty years, different studies have shown that blue and/or red light
can be used to treat mild to moderate acne. Blue light is recognized as
having anti-microbial properties and red light has also been shown to
have anti-inflammatory effects. Red light has been used to help heal
decubitus ulcers (bed sores), reduce the effect of herpes, accelerate
recovery of sprains and help in other situations.
More recently
researchers have shown that yellow and red light stimulate fibroblast
activity that leads to more collagen. This produces beneficial
photocosmetic effects on aging conditions such as fine lines, wrinkles,
rosacea, and photodamaged skin.
Frequently Asked Questions
How does Low
Intensity Light Therapy (LILT) work?
LILT actually works through several mechanisms. However, the most
widely identified mechanism involves mitochondria. Light stimulates the
production of Adenosine TriPhosphate (ATP) that is the basic energy unit
for cellular activity. ATP is then used in different ways by the body.
One way is to increase fibroblast activity which is another pretty basic
biological function. Fibroblasts can lead to increased collagen
formation. Collagen is the basic protein cell in the body and is a
major component of most tissue, particularly soft and connective
tissue. Another effect of light is increased blood circulation,
particularly microcirculation. Combine increased fibroblast activity
and increased microblood flow and you can understand why it has been
used for years to heal bed sores and other chronic wounds. But light
can affect the lymphatic system and elements in blood. Although
increased blood flow has long been thought to be a reason why many
people have been successfully treated to slow hair loss and grow hair, a
recent research report suggesta that it also effects blood components
similarly to minoxidil (Rogaine®.)
When LILT is used
with ALA or Levulan, the light activates a cascade of events that
produces singlet oxygen that kills nearby cells.
Are there
well-defined principles of LILT?
Yes. The following principles have been presented as “laws” so they are
well-defined.
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The immediate
effect of light hitting tissue is local but the secondary effect is
regional. An early indicator of this was when a bed sore on one leg
was treated and the untreated sore on the other leg responded as
well.
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There is a
Dosage Window. Too little light does no good and too much light stop
many effects.
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The effects are
cumulative. Several small treatments are better than one large
treatment
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The effects are
transient. Like many medicines, the effects go away when you stop
treatments. However, this is not always true as a muscle that has
healed with the help of LILT will stay healed. This is true in
applications like hair rejuvenation. |
Will I feel anything during LILT?
In straight LILT applications, you feel nothing. LILT works through
photobiostimulation. It is absolutely NON-THERMAL so there is no heat.
This is why LILT devices have been called cold lasers or soft lasers.
However, it is possible to feel some heat from the electrical
inefficiency of the light source. Less than 100% of the electrical
energy is converted to light energy. The difference is primarily given
off as heat. This is similar to the incandescent light bulb that you
know gets hot to the touch during use. But, the laser diode or LED does
not get hot to the touch. Instead, heat is produced in the electronic
circuitry behind the diode.
When LILT is used to activate ALA, you may feel the resultant chemical
reaction.
Must lasers be
used?
No. Light from LEDs, metal hydride, fluorescent and other light sources
have been demonstrated to be effective in many applications. For
example, acne has been treated successfully with light from LEDs, metal
halide lamps and flourescent tubes with and without Levulan.
Pioneering
physicians and researchers who started with lasers and moved on to laser
diodes used to say very firmly that lasers are required. Their reasons
are many including the unscrupulous early marketing of LED systems by
some people as lasers. However, they seem to have migrated to a
current position that laser diode application requirements are better
studied and understood and that LED treatments parameters are still
being defined. A representative of one of the larger laser diode system
manufacturers who also makes LED systems maintains that in superficial
applications both are effective. In deep tissue applications, lasers
are better.
What are the differences between lasers and LEDs?
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Both are monochromatic light sources. However, the band, or range,
of light waves is narrower for lasers than for most LEDs. For
example, a 670nm laser diode may emit lightwaves between 665 and
675nm whereas the lightwaves from a 660nm LED may range from 640 to
680nm. In most applications, the wider range does not change
results.
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Lasers emit light waves that are almost parallel whereas LED light
waves move in different directions.
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Laser light waves have similar photons moving in step in time and in
space (coherent) whereas LED light waves travel in all directions
and are not in step (incoherent.)
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Laser beams can be focused to extremely small spots where LED light
can focused but the spots are much larger. |
Does coherence and polarity make a difference?
Much of the
original work with what was then called Low Level Laser Therapy (LLLT)
was done in the old Soviet Union. Dr. Tina Karu is widely respected as
one of, if not the leading expert in the science of LLLT and now LILT.
She has repeatedly published that coherency makes no difference.
Other researchers have reached the same conclusion. The lack of effect
due to polarity has long been recognized since polarity is lost almost
immediately upon the light entering a biological target as is coherency.
So why do some of
the original researchers maintain lasers are better than LEDs? The
primary reason presented is that lasers, particularly the semiconductor
lasers most commonly used today, do not have perfectly uniform energy
distribution. Instead they have hot spots called speckles in which the
photons are packed much closer together. These photons may penetrate
deeper or, in some cases, actually produce localized thermal effects- be
they good or bad.
Do LEDs have any advantages over lasers?
Yes. Because they
are incoherent, they present no optical hazard to a person’s eyes. As a
result, higher power units can be sold for individual use. For
example, only Class IIIa lasers can be sold without restrictions to
individuals in the USA. Class IIIa lasers emit less than five (5)
milliwatts. However, since LEDs are incoherent and have been classed
as non-significant risk devices by the FDA, they can be more powerful
and still be safe. Generally this offsets any absorption advantage of a
laser. For example, if the light from a laser is absorbed 10% better by
a chromophore than that from an LED but the LED sends four times, or
400%, more photons by the chromophore, more are absorbed in less time.
How does that
benefit me?
It reduces the time for the application - significantly. For example,
most superficial applications require 2 to 4 Joules of energy. That is
2,000 to 4,000 millijoules. If you use a 5 milliwatt laser, it emits 5
millijoules. You will need 400 to 800 seconds or nearly seven to
fourteen MINUTES to deliver the required energy. BUT, if you use a LED
product that emits 100 millijoules, you will only need 20 to 40
SECONDS. Some practitioners say that about 40% more energy is required
with LEDs to get the same effect. That means you would finish the
application in 28 to 56 SECONDS rather than seven to fourteen
MINUTES.
I have read about a SuperPulsed LED system. What
is that?
Hype. The original surgical lasers had a pulse operating mode that
allowed the operator to set a pulse time shorter than he could turn the
laser On and Off using his foot pedal. This added precision to the
removal of tissue in microsurgery but did not really change the
characteristics of the laser beam as it operated in the continuous wave
mode. Carbon dioxide laser manufacturers developed a different type of
pulse with a different tissue effect. This became known as SuperPulse.
A very short but intense pulse of electrical energy was put into the
laser, creating a very short, intense pulse of laser light. The profile
of the pulse looked somewhat like a dagger. In the Surgilase 150XJ,
which became the gold standard of skin resurfacing lasers, the peak
power in the pulse was about eight to ten times the nominal output
before the pulse would end. Quantitatively, that meant that the 150
watt laser would produce a 1200 to 1500 watt beam for a few
microseconds. The tissue effect was very different from that of a
continuous wave beam even though the average powers were about the same
(the high power bursts cannot be maintained for long.)
LED manufacturers
say that a LED can be pulsed to about 2.5 times its nominal rating. 2.5
times 8 to 10 milliwatts isn’t much. So, if they are pulsed a few times
a second or 64,000 times per second, the output is still 20 to 25
milliwatts.
What is the
significance of pulsing?
Mixed. There has
been articles that say pulsing makes no difference. More recently,
there have been several articles or reports that claim different tissue
effects for different pulse rates. Some manufacturers claim “patent
pending frequencies" that have some unique effect. Peer reviewed
articles, those reviewed by fellow physicians, are the best source of
meaningful, definitive differences. That has not happened yet. Large
manufacturers of both laser and LED systems have always included pulsing
options for users who believe they are useful.
Do LEDs really
lasts 100,000 hours?
Some LEDs are described as having a 100,000 hours life. That is not
100,000 hours at full power though. Actually, it is the time until the
output has reached half the rated level. Light output starts to
deteriorate after the first twenty-four hours and drops off to half or
less around 100,000 hours. Typically, you will notice any change in
effect during the first 3,000 to 10,000 hours.
Can LILT cause
cancer?
No. A phenomenon that is not unique to LILT is that what happens in a
laboratory, in vitro testing, may not happen in life. This is true of
drugs as well as light. Although there have been several articles
reporting a negative effect of low intensity light on cancer cells in a
petri dish, there are no reports of a single case where it is suspected
to caused or contributed
to cancer in people. In fact, there are animal studies that show tumors
are either unaffected by light or tend to shrink and even disappear.
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