Laser therapy: Frequently asked questions
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What is laser therapy?
Laser therapy or Laser Phototherapy is a method where light from a laser is applied to tissue (or cells in culture) in order to influence cell or tissue functions with such low light intensity that heating is negligible. The effects achieved are hence not due to heating but to photochemical or photobiological reactions like the effect of light in plants. The lasers used are normally called therapeutic lasers or medical lasers.
How does it work?
Light energy enters the damaged cells and stimulates inter-cellular activity. This reduces pain in the area and speeds recovery of the damaged cells. Once the cells recover, the healing process is complete.
What is it used for?
Laser therapy may be used to:
- shrink or destroy tumours, polyps, or precancerous growths
- relieve symptoms of cancer
- remove kidney stones
- remove part of the prostate
- repair a detached retina
- improve vision
- treat hair loss resulting from alopecia or aging
- treat pain, including back nerve pain
Lasers can have a cauterizing, or sealing, effect and may be used to seal:
- nerve endings to reduce pain after surgery
- blood vessels to help prevent blood loss
- lymph vessels to reduce swelling and limit the spread of tumor cells
Lasers may be useful in treating the very early stages of some cancers, including:
- cervical cancer
- penile cancer
- vaginal cancer
- vulvar cancer
- non-small cell lung cancer
- basal cell skin cancer
For cancer, laser therapy is usually used alongside other treatments, such as surgery, chemotherapy, or radiation.
Laser therapy is also used cosmetically to:
- remove warts, moles, birthmarks, and sun spots
- remove hair
- lessen the appearance of wrinkles, blemishes, or scars
- remove tattoos
What should I expect during treatment?
Laser Therapy is a painless treatment that lasts an average of 8 minutes. You may experience a comfortable sensation at the point of application.
What can I expect after treatment?
Most people experience positive results in 1 to 3 treatments, with the average course of treatment being 7 to 10 sessions. Swelling is greatly reduced and there is a rapid relief of pain. Acute conditions usually subside quickly, typically within one phase of treatments, while chronic conditions can be controlled with regular treatments. The effects of MLS Laser Therapy are cumulative; therefore, expect to see improvement as you proceed through your treatment plan. It is critical that once you start, you complete the course of treatments recommended by your doctor or symptoms are likely to reoccur.
What are the risks?
Laser therapy has some risks. The risks for skin therapy include:
- changes in skin color
Is laser therapy scientifically well documented?
Basically yes. There are more than 130 double-blind positive studies confirming the clinical effect of low level laser therapy (LLLT). More than 3000 research reports are published. Looking at the limited LLLT dental literature alone (370 studies already in 1999), more than 90% of these studies do verify the clinical value of laser therapy. About 250 papers are annually published in peer reviewed scientific papers
Where do I find such documentation?
The book “Laser Therapy Handbook” is the best reference guide for literature documentation. Abstracts from scientific papers can be found on PubMed, http://www.pubmed.com
But I have heard that there are dozens of studies failing to find any effect of LLLT?
That is true. But you cannot just take any 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 flaws. 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 dosage, diagnosis, treatment technique and individual reaction.
Can therapeutic lasers injure your eyes?
Yes and no. Any strong light source – laser or not – can injure the eye. There are strong lasers that can cut in plastic and even steel. They can injure eyes and tissue, but laser pointers and therapeutic laser can normally not.
The risks different lasers pose to eyes are affected by the following factors:
- The output power (strength) of the laser
- The divergence of the light beam
- The exposure time
- The wavelength of the light
- The distribution of the light source
How do I know which laser I should buy?
The laser market is very complicated and full of pitfalls. How do you know which instruments are good? What is expensive? Will it be expensive in the long run to buy something cheap? It is easy to make hasty decisions when faced with a skilful salesman – who is likely to know much more about the field than the customer. Before you know it, you’ve signed on the dotted line. All lasers are given a laser class. This classification is only to indicate the possible eye risk and has nothing to do with the possible effectiveness in treatment. There are four laser classes where class 4 is the strongest and class 1, 2, 3A and 3B are less hazardous to eyes. Lasers in CD players and for reading bar codes are usually class 1 lasers while surgical and industrial lasers usually are class 4 lasers.
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 InGaAlP- or HeNe-laser has been used a great deal in dentistry in particular, as it was the first laser available. They are especially good for and have been used for wound healing for more than 40 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 keratoconjunctivitis with excellent results, that is, irradiation of the eye through the eye lid. 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 dosage 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.
* 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 dosages should be administered to mucous membrane! Most GaAs equipment is intended for extraoral use, but there are special lasers adapted for oral use.
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 fibre-optic light conductor which runs from the laser apparatus to the probe, but just a normal, cheap, robust electric cable. Optimum treatment dosages 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 myofacial 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 (InGaAlP laser) and GaAlAs laser. GaAs can, nevertheless, be used successfully on wounds in combination with HeNe or InGaAlP, but the dosages should be very low – under 0.5 J/cm2.
* The GaAlAs laser can have a wavelength in the interval 750 to 980 nm and has become increasingly popular. Most common wavelength is 808 nm. As they are very easy to run electrically, small rechargeable lasers have been put on the market, often not much larger than an electrical toothbrush. (They can run on normal or rechargeable batteries.). GaAlAs lasers have appeared on the market with an output of over 500 mW.
200-300 mW laser diodes are now relatively cheap and the GaAlAs laser gives “a lot of milliwatts for the money”. Recently, GaAlAs lasers have appeared on the market with an impressive output of over 500 mW. In Europe, GaAlAs laser with powers above 500 mW can only be used by doctors and dentists, being Class 4 lasers.
Many InGaAlP/GaAlAs lasers have well-designed, exchangeable, sterilizable intraoral fiber tips (light guides). For the infrared types especially, output power meters are essential because the light is invisible
Can carbon dioxide lasers be used for LLLT?
Yes. Therapeutic laser treatment with carbon dioxide lasers has become more and more popular. 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 a mm (unless focused to burn). Still, it does have biostimulative properties. So the effect most likely depends on transmittor 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 hair, 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 haemoglobin 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 also penetrate bone (as well as it can penetrate muscle tissue). Fat tissue is more transparent than muscle tissue.
For example: a InGaAlP laser with a power output of 35 mW has a greatest active depth of about 10 mm depending on the type of tissue involved. A GaAlAs probe of some strength has a penetration of 35 mm and a GaAs laser has a greatest active depth of between 30 and 40 mm (sometimes down to 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.N.B. Clothes will reduce penetration between 80 and 100% depending on thickness and colour
Can LLLT cause cancer?
The answer is no. No mutational effects have been observed resulting from light with wavelengths in the red or infra-red 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 can 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 tumours treated with LLLT can recede and completely disappear, although laser treatment had no effect on tumours over a certain size. It is probably the local immune system which is stimulated more than the tumour.
What happens if I use a too high dose?
You may have a biosuppressive effect or just a non optimal effect. That means that, for instance, the healing of a wound will take longer time than normally. Very high doses on healthy tissues will not damage them
Are there any contraindications?
No, no medical contraindications. In most countries there are legal contraindications, i.e. you should not treat cancer or some other serious diseases. Pregnancy is not a contra indication if treatment is done with common sense. Pacemakers are electronical and are not influenced by light. The most valid contraindication is possible lack of adequate medical treatment
Does LLLT cause a heating of the tissue?
Principally yes – all light will cause some heating if absorbed by tissue. However, stronger laser types like GaAlAs lasers in the 300-500 mW range may cause a noticeable heat sensation, particularly in hairy areas, dark tattoo and on sensitive tissues such as lips. The amount of melanin in the skin is an important factor; dark skin will be more heated than fair skin. The biological effects have nothing to do with heat. Due to increased circulation there is usually an increase of 0.5-1 degrees Celcius locally
Does it have to be a laser? Why not use monochromatic non coherent light?
Monochromatic non coherent light, such as light from LED’s can give good effect on superficial tissues such as wounds. In comparative studies, however, lasers have shown to be more effective than monochromatic non coherent light sources, especially in deep tissue.