TO REFRESH YOUR MEMORY
Low-level
laser therapy means light therapy with c o l d, low-energy and coherent
light. This light is safe, because it does not heat the tissue.
Therefore it belongs to laser class 3B! Here light is discharged in the
milliwatt range (up to a maximum of 500 mW).
Yet the term low-level
laser therapy is not protected. Some class 4 lasers are also low-energy
compared to surgical lasers with a very high power output. They work in a
range of up to 30 watt, and their light is w a r m. Therefore they
belong to laser class 4, which means they heat tissue and can be
dangerous. Thermal effects and skin burns can happen after just a few
seconds. Manufacturers of class 4 lasers claim: "Stronger is better.
Dangers can be excluded by using specific application techniques."
TO BE CLEAR FROM THE OUTSET
We do not claim that 4
lasers have no therapeutic effects! With certain orthopaedic
indications and when using suitable application techniques, they can no
doubt generate positive results. However, the crucial question is: Do we
need them? Are these effects stronger than with traditional low-level
lasers so that we should put up with the dangers that class 4 lasers
entail? Do they expand the application range and hence offer a genuine
advantage?
Our answer is: Definitely not. The contrary is true.
LET US COMPARE CLASS 3B AND 4 LASERS
Below we
compare the two laser classes with respect to their evidence, their
safety, and their effectiveness. Moreover, we comment on the claims made
by class 4 laser manufacturers.
1. EVIDENCE
During the past 40 years, 99% of
research on LLLT has been performed with class 3B lasers. There are more
than 300 RCTs and over 3,500 scientific studies on the effectiveness of
3B lasers. Manufacturers of class 4 lasers use the evidence of 3B
lasers to promote their products. Hardly any studies are available on
the effectiveness of class 4 lasers.
2. SAFETY
3B
lasers are not dangerous, they are safe. Even though a few
manufacturers claim the contrary, class 4 lasers are by no means
harmless. When applied improperly, they can quickly cause skin burns.
Especially in veterinary medicine, in which class 4 lasers are more
common, incidents keep happening.
We tested the heating of the tissue by a class 4 laser on a piece of meat (steak).
> Irradiating a Steak with a Class 4 Laser
> Temperature Comparison Class 3 ? Class 4
Depending
on the place and purpose of the application, the potential dangers of
class 4 lasers are more or less serious. With many applications, it must
be advised against using these lasers even if they are applied
"properly". These include, e.g., applications in the area of the eyes
and face, on the ear, mucous membranes, open wounds, for nerve
regeneration, in the case of dermatological indications, and conditions
which involve inflammations.
3. EFFECTIVENESS
Thesis 1: Higher power output = better tissue penetration = more effective
1. Wrong! because:
The modes of action in LLLT are of a biomodulatory nature and therefore depend primarily on the wavelength!
Biomodulatory
effects are mostly a consequence of the applied wavelength and its
absorption coefficient. After all, the purpose of LLLT is to impact the
cell's biochemistry. Different wavelengths have different medium
penetration depths in the skin of about 0.3 to 2 mm, which already at a
tissue depth of only 6 mm results in penetration differences between
0.000001 and 0.125 mm respectively. This is a factor of 125,000. By
contrast, the impact of the power applied is only marginal (e.g., 10,000
for a power difference of 5 mW and 5 W respectively)!
Due to the
critical importance of the wavelength, it is therefore also true that a
class 4 laser beam with a wavelength between 940 and 980 nm can
penetrate the skin less than a 3B laser with a wavelength between 800
and 900 nm.
2. Wrong! because:
In LLLT, the depth effect in the tissue is primarily based on amplification effects!
The
depth effect in LLLT is based on the "patient's internal amplification
effects" (PASER according to Mary Dason) which are triggered by LLLT.
LLLT does not require very high stimuli, as the primary effects in the
cell are set off by very low doses, while high doses have an inhibiting
effect. The enhancement and transfer of the effect takes place via
potentiating effects along the metabolism paths in the downstream and
the intercellular communication paths. This is precisely why LLLT is so
effective. In short: The depth effect in traditional LLLT with 3B lasers
already exists, and this precisely is LLLT!
Thesis 2: More is more helpful!
1. Wrong! because:
Hormesis is a characteristic of biological systems (Arndt-Schulz rule).
Ever
since laser therapy has existed, users have been told about the
so-called Arndt-Schulz rule, according to which weak stimuli promote
physiological processes, while strong stimuli inhibit them. Clinical
experience has confirmed this rule for decades and is well documented,
e.g. regarding the treatment of open wounds.
Even so, the argument
that more is better still stands a good chance to sound convincing
today. Partly in response to this indestructible notion, which is
largely fed by marketing strategies, the University of Massachusetts
founded its own association back in 2005: the International Dose
Response Society (see www.dose-response.org). Its purpose is to advance
the understanding of low-level effects and the associated phenomenon
that low doses stimulate while high doses inhibit. Research into
biological dose?effect relationships across the entire range from
promotion to destruction has great implications for many sciences. These
include medical disciplines such as toxicology, pharmacology,
neuroscience, immunology, physiology, and radiation biology.
The
research topic is hormesis, from the Greek for "to put in motion, to
trigger". Hormesis refers to the positive reaction of biological systems
to exposition of very low stimuli (such as toxins or other stressors).
They are also called "eustresses". Improvement through small doses and
inhibition through large doses can be illustrated by an upside-down
U-shaped curve. Its shape resembles that of the therapeutic dose window
for LLLT, which is based on clinical experience between stimulating and
cumulative negative effects due to low doses (mW range) and high doses
(W range) respectively.
2. Wrong! because:
An overdose has negative effects in LLLT.
Numerous
studies tell us that cellular metabolism mechanisms are inhibited by
excessive radiation doses. Since the beginnings of laser therapy,
inhibitory effects have mostly been ascribed to improper application in
the form of overdoses.
The reason is that in LLLT, the decisive
impact factor is not the radiation dose but the wavelength, on which the
impact on the cellular metabolism depends almost exclusively. With the
right wavelength, it can be achieved with even minimal doses of 0.1
Joule. Stimulation cannot be increased ad infinitum ? a physiological
system can work no better than perfectly. The physiological limits make
sense, and crossing and challenging them may cause great damage.
Therefore:
There exists no evidence for the claim that in LLLT more power means
greater effectiveness! There is, however, evidence for the exact
opposite!
Take a look at the following example:
Twenty-five RCTs
met the inclusion criteria for a systematic review and a meta-analysis
on the effectiveness of LLLT in the treatment of tendinopathies
conducted in 2010 (Tumilty et al. ?
http://www.ncbi.nlm.nih.gov/pubmed/19708800). Of these 25 studies, 12
had positive and 13 had negative results. The researchers were able to
demonstrate that the positive results were related to the fact that the
therapeutic dose windows were maintained (that is to say, the doses
recommended for LLLT) while the negative studies could be attributed to
overdoses.
Leading authorities on the research of the relationship
between dose and effect in LLLT and the greatest experts on LLLT
literature, such as Prof. Jan Bjordal, Dr. Jan Tunér and James Caroll,
have tirelessly explored these questions for years: How much laser is
enough? And how much is too much? How did negative study results come
about? And they never stop repeating:
Yes! There is a dose window in LLLT, and heeding it is crucial for its future and its acceptance!
3. Wrong! because:
Thermal effects are no primary effects of LLLT.
There
are studies which demonstrate that changes in the redox state of the
cell may also be triggered by photothermal (as opposed to
photobiomodulatory) effects, which might explain some therapeutic
effects of class 4 lasers. According to this explanation, 3B lasers
trigger photobiomodulatory processes, and class 4 lasers, photothermal
effects. Yet in the latter case, the transition between positive effects
that are induced via helpful thermal mechanisms in the cell and
inhibiting effects that are a result of overheating are extremely vague.
In specific cases, the tipping point depends on so many parameters
(such as type, tonus, and physiological age = stress elasticity of the
tissue) that it is difficult to conceive how it might be precisely
calculated.
By contrast, photobiomodulatory effects generate only
minimal thermal effects due to the cellular stimulation of the
metabolism and within the natural physiological margin.
4. RELIABLE DOSES
Manufacturers of class 4 lasers claim that dangers due to overdoses and skin burns are excluded because
the laser beam is expanded (i.e., not focused) and applied from a distance (which entails a great loss of intensity) and because
the laser beam is constantly moved, so that no excessive intensity can be generated at any one place.
Theoretically,
this is true: a class 4 laser is to be handled in such a way that it
becomes like a class 3 laser. The great expansion of the beam, treatment
from a distance, and constant movement of the laser are to neutralize
the dangers class 4 entails while maintaining the alleged advantages
that are a result of the greater power (in particular greater tissue
penetration). How is that supposed to be possible?
On the one hand
the greater power is supposedly more effective (which, as we have seen,
is already a basic misconception), and on the other, it is neutralized
from the start by the way in which it is to be handled so as to avoid
dangers. In plain English: it's a self-contradictory panacea.
Fact is
that when a class 4 laser is applied conscientiously, the same results
may be expected as with class 3B lasers ? at best.
Conscientious
application means: you know precisely the distance from which to
radiate, the degree by which the focus has to be expanded, and the
movement technique and speed that must be applied to remain within the
dose window that is effective with LLLT, and hence to avoid both
overdose and underdose. For when using this method, underdosing is by no
means impossible: by expanding the beam and moving it further away
reduces the beam density to such a degree that it is doubtful if the
same energy densities in the tissue can be achieved as with 3B lasers.
Assuming
that all adjustment measures for class 4 lasers could be defined so
precisely that a 3B laser could be simulated, these settings would
certainly have to be fixed. This would be possible with the help of
fixed scanners whose effective speed of movement and effective distance
to the tissue are ensured. Yet this is impossible with a handheld laser
unit.
Laser class | Class 3B | Class 4 |
Evidence | very high | Minimal Please note: The evidence in LLLT literature was generated with 3B lasers It does n o t apply to class 4 lasers! |
Safety | very high | Danger of burns |
Effectiveness
|
|
|
Cost-effectiveness | The fibre-optic cables used with laser class 4 are considerably more expensive than those of class 3 lasers and have a tendency to break. |
CONCLUSION
Class 4 lasers are not lasers in the
context of LLLT in the sense in which the term has been used in science
and actual practice for 50 years.
Class 4 lasers are potentially
dangerous without offering advantages either regarding penetration depth
in the tissue or regarding depth effectiveness.
Class 4 lasers might
be able to achieve similar results in certain instances in the
treatment of orthopaedic diseases. However, the results are difficult to
calculate. So are therefore the contrary effects due to overdoses and
underdoses.
MORE IS NOT ALWAYS BETTER!