Time for A Change Written by Dr. Jan Tunér
Time for A Change
By Dr. Jan Tunér
Is It Time to Consider Photobiomodulation As a Drug Equivalent?
By Tiina Karu, PhD, DrSci

Laser phototherapy (LPT) is an exciting an extremely promising treatment modality. Yet it has been struggling uphill for 40 years, constantly criticized, met with disbelief and prejudice. And the laser community has been in a defensive position all the time. Isn’t it time for a change? What do we actually know about LPT? I ask myself - and give myself the answers, just to make sure the answers are the correct ones…

1 Is biomodulation with laser light fact or fiction?
  Hard fact when it comes to in vitro effects. Good fact in the animal experimental set-up.
2 Is there enough scientific proof about the clinical effects?
  Not as much as we would like, but just as much or more than several traditional medical therapies.
3 Which is the major problem in research?
  The plethora of parameters, such as energy, dose, pulsing, number of sessions, wavelengths.
4 Is there enough information on PubMed?
  What is enough? But more than 200 papers annually for the past six years is not bad.
5 Why then still all these skeptics?
  They are either ignorant or just not updated. Or, in the best of cases, very prudent. That is OK with me.
6 What has caused all these negative attitudes?
  Poor and meager studies in the 80s and 90s, especially from researchers not really understanding what they were doing. Typical for new methods.
7 Any other reasons?
  Yes, since LPT works in so many medical indications, most areas have rather few studies, whereas in the pharmaceutical industry each “pill” receives its own and focused research. So the beauty of the therapy is in itself one of the obstacles at the moment.
8 Why is disbelief still prevailing here and there?
  Partly because of lack of qualified peer reviewers in scientific journals and because of too many poor laser manufacturers.
9 What do you (I) mean by poor?
  Poor of resources to sponsor research. Also in too many instances poor in responsibility.
10 Is LPT part of mainstream medicine?
  Not yet. It is in a borderline area between animal and clinical science for most indications.
11 Why are there then not studies enough proving the efficacy and cost effectiveness of LPT?
  Again, lack of resources, catch 22!
12 Would then larger clinical studies prove it?
  Yes, in a dozen of indications, provided persons understanding LPT are leading the studies.
13 Is the pharmaceutical industry fighting LPT?
  Don’t think they are, but if they knew better, they would.
14 Why are so many doctors negative to LPT?
  Because they are heavily influenced by the rich pharmaceutical industry.
15 What will change the situation?
  A number of retirements. And a constant strife for quality in LPT research. Only facts will do.
16 What can I do about it?
  Stop being defensive. You don’t have to be offensive (meaning rude), just stick to your conviction and stand up for it. You probably know more than the skeptics.
17 Will you (I) regret publishing this?
  Probably. As Winston said: “Speak in anger and you will present the best speech you will ever regret”.

Change will come!
Jan Tunér


  Frequently Asked Questions
1) What is LASER?
2) What is LLLT?
3) What is LILT, LPLT, therapeutic laser, soft laser, MID laser….etc.
4) Who are the pioneers of low level laser therapy?
5) Is laser therapy scientifically well documented?
6) Where do I find such documentation?
7) But I have heard that there are dozens of studies failing to find any effect of LLLT?
8) What other conditions does the Low Level Laser help treat?
9) Is Low Level Laser Therapy safe and is there any side effect?
10) How does it work?
11) Is this a temporary fix to my problem?
12) Which lasers can be used in medicine?
13) How come some LLLT equipment has power in watts and some only in milliwatts?
14) What are the most common laser types in LLLT?
15) How deep into the tissue can a laser penetrate?
16) Which type of laser is best suited to which job?
17) Can carbon dioxide lasers be used for LLLT?
18) How deep into the tissue can a laser penetrate?
19) Can LLLT cause cancer?
20) What happens if I use a too high dose?
21) Are there any counter indications?
22) Will I feel anything?
23) Does LLLT cause a heating of the tissue?
24) Does it have to be a laser? Why not use monochromatic non-coherent light?
25) Does the coherence of the laser light disappear when entering the tissue?
26) What are the two major differences between laser light and conventional light?
27) What does radiation mean when you are speaking of Lasers?
28) What is a joule?
29) What are the biological effects of laser light emitted from LLLT devices Laser?
30) Can therapeutic lasers damage the eye?
31) Which frequency (pulsing) should be used for the various therapies?
32) How many treatments will I need, and how often will I need to get the treatments?
  Questions & Answers
  What is LASER?

LASER stands for Light Amplification by Stimulated Emission by Radiation.

  What is LLLT?

Low Level Laser Therapy (LLLT) is the new internationally accepted term for biostimulation with low energy lasers in order to achieve therapeutic desired effects.
Light or photon energy with the unique property of being able to penetrate up to two inches below the skin surface causing an increase in cellular metabolism with no tissue damage whatsoever.
Low level laser therapy, sometimes also referred to as cold laser therapy is quickly becoming the first line of attack in pain control and tissue healing in rehabilitative medicine.
Laser treatment in which energy output is low enough so that the temperature of the treated tissue does not rise above 98.6 F (normal body temperature). Low level laser therapy is safe, painless, and non-invasive and the results are often immediate and sustainable.

  What is LILT, LPLT, therapeutic laser, soft laser, MID laser….etc.?

In the literature LILT (Low Intensity Laser Therapy) and LPLT (Low Power Laser Therapy) is also frequently used.
Therapeutic Laser:
Regarding the laser instrument, chose to use the term "therapeutic laser" rather than "low level laser" or "low power laser", since high level lasers are also used for laser therapy.
Soft Laser:
The term "soft laser" was originally used to differentiate therapeutic lasers from "hard lasers", i.e. surgical lasers.
MID Laser; Medical Laser:
Several different designations then emerged, such as "MID laser" and "medical laser".
Bio-stimulation laser
Bio-regulating laser
has been proposed with the disadvantage that one can also give inhibiting doses.
Low-reactive-level Laser, Low-intensity-level Laser
Photo-biostimulation laser and Photo-biomodulation laser are other names.

Thus, it is obvious that the question of nomenclature is far from solved.
This is because there is a lack of full agreement internationally, and the names proposed thus far have been rather unwieldy. Feel free to forget them, but remember laser therapy or LLLT until agreement is reached on something else.

  Who are the pioneers of low level laser therapy?

The first systemic scientific research on the biological effects of low level laser was conducted by the late Professor Endre Mester of the Semmelweis Medical University in Budapest, Hungary, 1966.

  Is laser therapy scientifically well documented?

Basically yes.
LLLT has been in active and beneficial use in Europe for nearly 30 years. There are more than 100 double blind positive studies confirming the clinical effect of LLLT. Over 2,500 clinical studies and published research reports have shown the effectiveness of LLLT for a variety of health issues. Looking at the limited LLLT dental literature alone (370 studies), more than 90% of these studies do verify the clinical value of laser therapy.
LLLT has been a staple in veterinary practices for decades.
In the past 6 years, professional sports teams have begun utilizing LLLT.

  Where do I find such documentation?

The book of authors Tunér and Hode “The Laser Therapy Handbook" is a reference guide as well as a wealth of laser therapy knowledge. The book contains 600 pages, multicolored and loaded with new information about the clinical and scientific aspects of laser therapy. Among other things there are about 1400 references.

  But I have heard that there are dozens of studies failing to find any effect of LLLT?

That is true. But you can not just take a laser and irradiate for any length of time and using any technique. A closer look at the majority of the negative studies will reveal serious flaw. Look for link under Laser literature and read some examples. But LLLT will naturally not work on anything. Competent research certainly has failed to demonstrate effect in several indications. However, as with any treatment, it is a matter of dose, diagnosis, treatment technique and individual reaction.


What other conditions does the Low Level Laser help treat?


Low Level Laser is being used to treat a variety of painful and inflamed conditions of the soft tissues and joints.

  • Knee Pain
  • Joint Pain in knees, hands, ankles, and hips
  • Arthritis, Osteoarthritis, Rheumatoid Arthritis
  • Chronic neck, back, and shoulder pain
  • Carpal Tunnel Syndrome
  • Rotator Cuff Injury
  • Sport injuries
  • Bursitis
  • Tennis Elbow and Golfer’s elbow
  • Fibromyalgia
  • Plantar Fascitis
  • Headaches
  • Tendonitis
  • TMJ
  • Other Musculoskeletal injuries
  Is Low Level Laser Therapy safe and is there any side effect?

In the past 4 years, the FDA has ruled that LLLT (Low Level Laser Therapy) is safe and the only contraindication (warning) is not to use it directly in the eyes.
For the past 30 years the technology of Low Level Laser Therapy (LLLT) has been formally accepted in many parts of the world such as Europe, Scandinavia, Russia and Japan. In all this time there have been no recorded long-term adverse effects from its use. It is considered to be non-invasive, painless and safe.
The question is often asked "If it's a laser aren't they used in surgical operations, to cauterize tissue?" The answer is "Yes" - Hot Lasers are able to cauterize (cut) tissue. However, the ones we use are "Low Level Laser" with designed parameters that make it impossible to damage even one cell in the body. Our lasers stimulate and energize the cells.
Industry has been using laser diodes for years in such applications as bar code readers, CD players, DVD players, laser printers and pointers. The FDA has listed bio-stimulation lasers as non-significant risk (NSR) devices.
The low level lasers shown here have received UL and CE approval for safety.

  How does it work?

All light has an effect on the cells of the human body. What that effect is shall be determined by the wavelengths of light applied. The low level laser produces a beam of light that has a specific wavelength and frequency. When the light of the laser is applied around the tissue, the electromagnetic energy is converted to chemical energy within each cell which sets in motion a chain of chemical reactions allowing the healing process to begin. This chemical reaction in the cell allows several things to occur.

  • Stimulates Healing and Repair of Tissue
  • Increases Tissue Strength
  • Reduces Pain: by stimulating cells to produce their own endorphins, a natural pain killer. Pain results from trauma, cellular disruption, malfunction, or less than optimal cellular function. Healing and pain relief come with cellular normalization. Photons enable cells to perform optimally by stimulating them to initiate bio-chemical reactions which produce enzymes and ATP (usable energy).
  • Reduces Inflammation: by suppressing inflammatory enzymes and enhancing the release of anti-inflammatory enzymes as much as 75%.
  • Decrease Swelling: by stimulating lymphatic drainage
  • Promotes Faster Wound Healing: by stimulating cells to increase the production of two major healing enzymes by as much as 75%, enhances lymphatic drainage thereby increasing circulation and speeding healing.
  • Increase Bone Repair Speed: by stimulating fibroblastic and osteoblastic proliferation
  • Stimulates Nerve Function
  • Promotes Cellular Oxygenation/Detoxification
  • Release Tight Muscles and Muscle Spasms: (both smooth and striated) that help create chronic pain, join problems and decreased mobility.
  • Enhance the Immune System: by increasing the number of "killer" cells by 400-900%.
  • Re-energize Cell Membranes: to allow transport of essential nutrients across cell walls (nutrients will not cross an injured or sick cell wall, thus slowing healing) allowing a healthy new cell to grow.
  Is this a temporary fix to my problem?

The good news is for most patients that have completed our Low level Laser Knee Program the results from the treatments have been sustainable. While some patients get immediate results, others usually require 6-12 treatments before there is a lasting effect. Since each person’s condition varies in severity the doctor will determine after reviewing your condition if laser treatments may benefit you.

  Which lasers can be used in medicine?

Examples of lasers that can be used in medicine:
Laser name Wavelength Pulsed Use in medicine or continuous

  • Crystalline laser medium:
    Ruby 694 nm p holograms, tattoo coagulation
    Nd: YAG 1 064 nm p coagulation
    Ho: YAG 2 130 nm p surgery, root canal
    Er: YAG 2 940 nm p surgery, dental drill
    KTP/532 532 nm p/c dermatology
    Alexandrite 720-800 nm p bone cutting
  • Semiconductor lasers:
    GaAs 904 nm p biostimulation
    GaAlAs 780-820-870 nm c biostimulation, surgery
    InGaAlP 630-685 nm c biostimulation
  • Liquid laser:
    Dye laser (tunable) p kidney stones
    Rhoda mine: 560-650nm c/p PDT, dermatology,
  • Gas lasers:
    HeNe 633, 3 390 nm c biostimulation
    Argon 350-514 nm c dermatology, eye
    CO2 10 600 nm c/p dermatology, surgery
    Exciter 193, 248, 308 nm p eye, vascular surgery
    Copper vapor 578 nm c/p dermatology

There are many other types, but those mentioned above are the most common.

  How come some LLLT equipment has power in watts and some only in milliwatts?

This applies to GaAs lasers. When a GaAs laser works in a pulsed fashion, the laser light power varies between the peak pulse output power and zero. Then usually the laser's average power output is of importance, especially in terms of dose calculation. The peak pulse power value is of some relevance for the maximum penetration depth of the light. Some manufacturers specify only the peak pulse output in their technical specifications. "70 milliwatts peak pulse output" naturally seems more impressive than 35 milliwatts average output! Rule of thumb is: Take the "watt peak pulse" figure, divide by 2, and you have the average output in mW. This rule of thumb is not valid for GaAs-lasers as these lasers are super pulsed (extremely low duty cycle).

  What are the most common laser types in LLLT?

Helium-Neon (HeNe) - visible, red
AlGaInP- visible, red
Gallium-Arsenide (GaAs) - invisible, infrared
Gallium-Aluminum-Arsenide (GaAlAs) - invisible, infrared

  What is the difference between visible red lasers and invisible, infrared lasers?

Visible red lasers penetrate the skin poorly, therefore are more suitable for superficial (skin and mucosal) lesions, superficial muscle and connective tissue injuries.
Infrared lasers, such as the HB-750 Laser penetrate deeper and are suitable for both superficial and deeper lesions.

  Which type of laser is best suited to which job?

There are three main types of laser on the market: HeNe (now being gradually replaced by the InGaAlP laser), GaAs and GaAlAs. They can be installed in separate instruments or combined in the same instrument.
The HeNe laser or InGaAlP laser has been used a great deal in dentistry in particular, as it was the first laser available. The HeNe laser has been used for wound healing for more than 30 years. One advantage is the documented beneficial effect on mucous membrane and skin (the types of problem it is best suited to), and the absence of risk of injury to the eyes. A Japanese researcher has even treated calves with kerato conjunctivitis with excellent results, that is, irradiation of the eye through the eyelid. Because HeNe light is visible, the eye's blink reflex protects it.
Normal HeNe output for dental use is 3-10 mW, although apparatus with up to 60 mW is available. An optimal dose when using a HeNe laser for wound healing is 1-4 J/cm2 around the edge of the wound, and approximately 0.5 J/cm2 in the open wound. HeNe lasers are used to treat skin wounds, wounds to mucous membrane, herpes simplex, herpes zoster (shingles), gingivitis, pains in skin and mucous membrane, conjunctivitis, etc.
It should be noted that HeNe fibers couldn't’t be sterilized in an autoclave. The alternative is to use alcohol to clean the tip, or to cover it with cling-film or a thermometer sleeve.
The GaAs laser is excellent for the treatment of pain and inflammations (even deep-lying ones), and is less suited to the treatment of wounds and mucous membrane. Very low doses should be administered to mucous membrane! Most GaAs equipment is intended for extra oral use, but there are special lasers adapted for oral use.
A GaAs laser needs an integral output meter that shows that there is a beam and its strength in milliwatts - this is necessary because the light this type of laser emits is invisible. Protective glasses for the patient may be appropriate in view of the invisible nature of the light.
In older systems the power output of conventional apparatus follows pulsation. This means that a GaAs laser with an average output of 10 mW when pulsing at 10,000 Hz only produces 1 mW when pulsed at 999 Hz and at 100 Hz only 0.1 mW. If you therefore want to administer treatment at low frequencies around e.g. 20 Hz (for the treatment of pain), the output power is, clinically speaking, unusable. However, there are GaAs lasers with "Power Pulse", which means that the power output is held constant at all pulse frequencies. This would be of interest to a physiotherapist, for example, when one considers that the GaAs laser has the deepest penetration of the common therapeutic lasers. Large doses can be administered to deep-lying tissue over a short period of time. A GaAs multi-probe can also shorten treatment times for conditions involving larger areas (neck/shoulders).
The GaAs laser is, like GaAlAs and InGaAlP lasers, a semiconductor laser. A purely practical advantage of this type of laser is that the laser diode is located in the hand-held probe. This means that there is no sensitive fiber-optic light conductor, which runs from the laser apparatus to the probe, but just a normal, cheap, robust electric cable. Optimum treatment doses with GaAs lasers are lower than with HeNe lasers. The GaAs laser is most effective in the treatment of pain, inflammations and functional disorders in muscles, tendons and joints (e.g. epicondylitis, tendonitis and Myofascial pain, gonarthrosis, etc.), and for deep-lying disorders in general. As mentioned above, GaAs is not thought to be as effective on wounds and other superficial problems as the HeNe laser T (InGaAlP laser) and GaAlAs laser. GaAs can, nevertheless, be used successfully on wounds in combination with HeNe or InGaAlP, but the doses should be very low - under 0.1 J/cm2.The GaAlAs laser has become increasingly popular. GaAlAs lasers have appeared on the market with an impressive output of over 2 W.
There are several types of GaAlAs-lasers. The most well documented type emits a continuous, invisible or barely visible light with the wavelength 820 nm. This laser assume an intermediate position as compared to the two other laser types, often proving effective on such skin conditions as leg ulcers but also, at least to some extent, on the problems of muscles, tendons and joints.
Many GaAlAs lasers have well-designed, exchangeable, sterilisable intraoral probes. Output meters are essential because the light from this type of laser is largely invisible.

  Can carbon dioxide lasers be used for LLLT?

Yes. Therapeutic laser treatment with carbon dioxide lasers has become more and more popular, sometimes called EDL-laser (emitted defocused laser). This does not require instruments expressly designed for that purpose. Practically any carbon dioxide laser can be used as long as the beam can be spread out over an appropriate area, and as long as the power can be regulated to avoid burning. This can always be achieved with an additional lens of germanium or zinc selenide, if it cannot be done with the standard accessories accompanying the apparatus.
It is interesting to note that the CO2 wavelength cannot penetrate tissue but for a fraction of an mm (unless focused to burn). Still, it does have biostimulative properties. So the effect most likely depends on transmitter substances from superficial blood vessels. Conventional LLLT wavelengths combine this effect with "direct hits" in the deeper lying affected tissue.

  How deep into the tissue can a laser penetrate?

The depth of penetration of laser light depends on the light's wavelength, on whether the laser is super-pulsed, and on the power output, but also on the technical design of the apparatus and the treatment technique used. A laser designed for the treatment of humans is rarely suitable for treating animals with fur. There are, in fact, lasers specially made for this purpose. The special design feature here is that the laser diode(s) obtrude from the treatment probe rather like the teeth on a comb. By delving between the animal's hairs, the laser diode's glass surface comes in contact with the skin and all the light from the laser is "forced" into the tissue. A factor of importance here is the compressive removal of blood in the target tissue. When you press lightly with a laser probe against skin, the blood flows to the sides, so that the tissue right in front of the probe (and some distance into the tissue) is fairly empty of blood. As the hemoglobin in the blood is responsible for most of the absorption, this mechanical removal of blood greatly increases the depth of penetration of the laser light.
It is of no importance whether the light from a laser probe, held in contact with skin is a parallel beam or not.
There is no exact limit with respect to the penetration of the light. The light gets weaker and weaker the further from the surface it penetrates. There is, however, a limit at which the light intensity is so low that no biological effect of the light can be registered. This limit, where the effect ceases, is called the greatest active depth. In addition to the factors mentioned above, this depth is also contingent on tissue type, pigmentation, and dirt on the skin. It is worth noting that laser light can even penetrate bone (as well as it can penetrate muscle tissue). Fat tissue is more transparent than muscle tissue.
For example: a HeNe laser with a power output of 3.5 mW has a greatest active depth of 6-8 mm depending on the type of tissue involved. A HeNe laser with an output of 7 mW has a greatest active depth of 8-10 mm. A GaAlAs probe of some strength has a penetration of 35 mm with a 55 mm lateral spread. A GaAs laser has a greatest active depth of between 20 and 30 mm (sometimes down to 40-50 mm), depending on its peak pulse output (around a thousand times greater than its average power output). If you are working in direct contact with the skin, and press the probe against the skin, then the greatest active depth will be achieved.

  Can LLLT cause cancer?

The answer is no. No mutational effects have been observed resulting from light with wavelengths in the red or infrared range and of doses used within LLLT. But what happens if I treat someone who has cancer and is unaware of it? Can the cancer's growth be stimulated? The effects of LLLT on cancer cells in vitro have been studied, and it was observed that they could be stimulated by laser light. However, with respect to a cancer in vivo, the situation is rather different. Experiments on rats have shown that small tumors treated with LLLT can recede and completely disappear, although laser treatment had no effect on tumors over a certain size. It is probably the local immune system, which is stimulated more than the tumor.
The situation is the same for bacteria and virus in culture. These are stimulated by laser light in certain doses, while a bacterial or viral infection is cured much quicker after the treatment with LLLT

  What happens if I use a too high dose?

You will have a biosuppressive effect. At least if you try to heal of a wound or treat for hair loss, then it will take longer time than normally. Very high doses on healthy tissues will not damage them.

  Are there any counter indications?

You should not treat cancer, for legal reasons. Pregnant women are not a counter indication, if used with common sense. Pace makers are electronically, do not respond to light. Epilepsy may be a counter indication. The most valid counter indication is lack of medical training.

  Will I feel anything?

No. Low level lasers do not generate perceivable heat. Therefore, when the laser contacts the skin the patient experiences no burning as a result of the laser. Most people feel nothing at all while a few may feel a slight tingling during the treatment.

  Does LLLT cause a heating of the tissue?

Due to increased microcirculation there is usually an increase of 0.5~1 centigrade locally. The biological effects have nothing to do with the heat. Our patented taped-laser module plays a roll of laser beam reflection shield, makes more microcirculation. Therefore, an increase of 2~3 centigrade in the attached part is normal. Other GaAlAs lasers in the 300-500 mW or higher range will cause a noticeable heat sensation, particularly in hairy areas and on sensitive tissues such as lips.

  Does it have to be a laser? Why not use monochromatic non-coherent /LED/other types of standard light?

Light emitted from a laser diode is monochromatic (having only one wavelength), parallel and coherent (having waves with similar direction, amplitude, and phase). These qualities make laser light much more valuable for therapeutic benefits.
Monochromatic non-coherent light, such as light from LED's can be useful for superficial tissues such as wounds. In comparative studies, however, lasers have shown to be more effective than monochromatic non-coherent light sources. Non-coherent light will not be as effective in deeper areas.
Laser light has unique physical properties, which no ordinary light has. This is the key to why laser light is so effective compared to other kinds of light in healing. 
LED based systems have gradually improved during the years and are now better documented. Because of lack of scientific support in the past, some manufacturers have quoted laser research as proof of the effectiveness of LED therapy, meaning that they are one and the same. Such argumentation should be a “warning lamp” to the customer.
LED’s can easily be arranged in “clusters” to cover large areas, while this is quite possible but less common with lasers. Combining LED’s and lasers in the same cluster is sometimes found, but the usefulness has not been documented.

  Does the coherence of the laser light disappear when entering the tissue?

No. The length of coherence, though, is shortened. Through interference between laser rays in the tissue, very small "islands" of more intense light, called speckles occur. These speckles will be created as deep as the light reaches in the tissue and within a speckle volume, the light is partially polarized. It is easy to show that speckles are formed rather deep down in tissue and the existence of real speckles proves that the light is coherent.

  What are the major differences between laser light and conventional light?

Laser light is monochromatic (narrow spectrum, specific wavelength) and coherent

  What does radiation mean when you are speaking of Lasers?

"Radiation" is often misinterpreted since it is also used to describe radioactive materials and ionized radiation. The use of the word "radiation" in terms of laser light is merely an expression of energy transmission.



  What is a joule?

A joule is a measure of energy generated by laser.

  What are the biological effects of laser light emitted from LLLT devices Laser?

• Increased cell metabolism
• Simulated cell growth
• Cell regeneration
• Increased tissue activity
• Anti-inflammatory
• Edema reduction
• Reduced fibrous tissue formation
• Stimulated nerve function
• Collagen deposition

  Can therapeutic lasers damage the eye?

Yes and no! Read the following:
The following factors are of importance regarding the eye risk of different lasers:
The divergence of the light beam. A parallel light beam with a small diameter is by far the most dangerous type of beam. It can enter the pupil, in its entirety, and be focused by the eye's lens to a spot with a diameter of hundredths of a millimeter. The entire light output is concentrated on this small area. With a 10 mW beam, the power density can be up to 12,000 W/cm2 the output power (strength) of the laser. It is fairly obvious that a powerful laser (many watts) is more hazardous to stare into than a weak laser.
The wavelength of the light within the visible wavelength range, we respond to strong light with a quick blinking reflex. This reduces the exposure time and thereby the light energy which enters the eye. Light sources which emit invisible radiation, whether an infrared laser or an infrared diode, always entail a higher risk than the equivalent source of visible light. Radiation at wavelengths over 1400 nm is absorbed by the eye's lens and is thus rendered safe, provided the power of the beam is not too high. Radiation at wavelengths over 3,000 nm is absorbed by the cornea and is less dangerous.
The distribution of the light source
If the light source is concentrated, which is often the case in the context of lasers, an image of the source is projected on the retina as a point, provided it lies within our accommodation range, i.e. the area in which we can see clearly. A widely spread light source is projected onto the retina in a correspondingly wide image, in which the light is spread over a larger area, i.e. with a lower power density as a consequence. For example: a clear light bulb (which is apprehended as a more concentrated light source) penetrates the eye more than a so-called "pearl" light bulb. A laser system with several light sources placed separately, such as a multi-probe (the probe is the part of the laser you hold and apply to the area to be treated; a single probe means there is only one laser diode in the probe, as opposed to a multi- probe, which has several laser diodes) with several laser diodes, can, seen as a whole, be very powerful but at the same time constitute a smaller hazard to the eye than if the entire power output was from one laser diode, because the diodes' separate placement means that they are reproduced in different places on the retina.
We have often heard this kind of remark: "If it's a class 3B laser then it's fine, otherwise it has no effect. This is of course entirely incorrect and has lead to a situation where manufacturers have produced lasers to meet the 3B classification, so that they will sell in greater volumes. Let us look at a couple of examples:
A GaAlAs laser with a wavelength of 830 nm, an output of 1 mW and a well collimated beam (1 mrad divergence) is classified as laser class 3B as it is judged to be hazardous to the eyes. The reason for this is partly the collimated beam, and partly the wavelength, which is just outside the visible range and hence provokes no blink reflex in strong light.
A HeNe laser with a wavelength of 633 nm, an output of 10 mW and divergent beams (1 rad divergence, which corresponds to a cone of light with a top angle of about 57°) is classified as laser class 3A because, owing to its divergence, it cannot damage the eyes.
With the recent advent of "high power low power lasers", i.e. GaAlAs lasers in the range 100-500 mW there is another story. These lasers are indeed dangerous for the eyes and should only be used by qualified persons and with proper protective measures taken.

  Which frequency (pulsing) should be used for the various therapies?

First we must differentiate between “chopping” and “super pulsing”. Some lasers, like the GaAs laser, are always pulsed. The pulses are very short but the peak power in the pulse is very high, several watts, but the pulse duration is typically only 200 nanoseconds. Other lasers like the HeNe and the GaAlAs are always continuous, but can be “pulsed” by mechanical or electrical devices. This means that the beam is turned off and on but the output of each pulse is still the same.
When pulsing one generally loses power. With most GaAs lasers the power decreases with lowered frequencies (unless there is a pulse train arrangement) and with “chopped” lasers, we typically loose 50% (50% duty cycle). The output is of course the same in the pulses but since it is turned off 50% of the time, treatment time must be extended.
There is sound evidence from cell studies that the pulsing makes a difference. But the evidence from clinical studies is almost absent. Since GaAs is always pulsed, we have to choose a frequency and then to use the anecdotal evidence there is. But the loss of power on lowered frequencies must be observed! For other lasers the choice of frequency is pure guesswork.

  How many treatments will I need, and how often will I need to get the treatments?

In order to heal the tissues quickly and to maintain the cells in biostimulation, a patient comes in for a treatment several times a week for a half hour each time. The average number of treatments can range anywhere from 15-25, depending on the severity of the condition. The less severe or acute the condition, the fewer number of treatments required. The more severe or more chronic the condition, the greater the number of treatments required.

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