Once reserved for the operating room, lasers are finding their way into exam rooms. But what is a laser? Does low-level laser therapy actually work? Is laser therapy legitimate? Read on for the 6 things everyone should know about laser therapy.
History of Laser Therapy
Light therapy has been used in various medical applications for over 40 years. It was first used in the 1970s to facilitate healing of chronic wounds. According to Diowave, one manufacturer of office-based laser therapy, “we offer care providers the ability to treat pathologies with results never before seen in Insurance or Government based medicine.” That’s a pretty big claim. Let’s back up a little bit and discuss some basics.
1. What is a laser?
The folks at NASA define a laser as “a very narrow beam of light that is useful in many technologies and instruments.” The word laser is actually an acronym and stands for Light Amplification by Stimulated Emission of Radiation.
Laser light is completely artificial–there is no natural equivalent. Lasers produce tightly focused beams of monochromatic light in which all of the light waves are in sync, or phased. This is the single most important feature of a laser and what really sets it apart from other light sources like LED.
Not all lasers are created equal, however. The first significant distinction among lasers is the material used to amplify the energy. Some are gas-based using CO2 for a medium. Others are considered solid-state like the Yag laser which uses Yttrium Aluminum Garnet.
The most common laser you’re likely to come across, however, utilizes a diode (diode = two terminals, unidirectional flow). Diode lasers are also referred to as semiconductor lasers. The material used to amplify the energy, in any case, is called the “lasing material”. Your average laser pointer is a diode laser that might use a mix of materials such as aluminum, gallium, arsenic, phosphorus, or indium.
The difference between a laser and an LED
So is a light-emitting diode (LED) the same as a laser diode? No. “LEDs (Light Emitting Diodes) are different from laser diodes and are not subject to the Federal laser product performance standard.”
Lasers (read: phased light waves) can produce a single shade of light anywhere along the visible and non-visible spectrum. The visible light spectrum, as you may recall, is roughly between 400 and 800 nm. The wavelength produced depends on the lasing material.
Light from an LED, on the other hand, is not phased or coherent. Unlike standard bulbs, LEDs can be directional but still contain many different wavelengths that fluctuate randomly.
The Four Laser Categories
The FDA classifies lasers into four categories based on a potential to cause harm:
- Non-hazardous (i.e. CD players)
- Potentially hazardous (barcode scanners)
- a) Momentarily hazardous (laser pointers)
b) Immediately hazardous (industrial lasers)
- Immediately hazardous, may start a fire (medical lasers)
When discussing laser treatments for medical applications, it’s also important to know the wavelength (measured in nanometers), and power (measured in milliwatts). The wavelength corresponds to the body tissue that will absorb the energy, another fundamental concept to laser therapy. The targeted tissue absorbing the energy is called a chromophore. Common chromophores include melanin, hemoglobin, and tattoo ink.
2. Which lasers have proven medical applications?
CO2 lasers are common in dermatology. They are considered “ablative” and are used for AKs, SKs, warts, and scars to name a few. CO2 lasers produce a wavelength of 10,600 nm.
Er:YAG (YAG doped with erbium) lasers operate at 2940 nm and are also used for improving skin texture and for remodeling a rhinophyma.
Vascular lasers operate between 500 and 1000 nm to treat telangiectasias and angiomas. Examples of vascular lasers include the Nd:YAG (YAG + neodynium) and diode lasers. These types of lasers are also used for cosmetic purposes such as hair and tattoo removal and skin resurfacing.
Excimer lasers are ultraviolet gas lasers that are used in the LASIK procedures. One common device in this arena uses argon and fluorine as a lasing medium and operates at around 190 nm, below the visible spectrum.
Intense pulse light, or IPL devices, are not lasers but filtered flashlamps that emit light in a wide range of wavelengths. IPL devices are dimmer and less powerful than lasers but can still be used for freckles, age spots, and wrinkles.
3. What other types of lasers are used in a clinical setting?
Low-level lasers are also known as cold lasers or photobiomodulation lasers. These types of lasers are almost exclusively employed by chiropractors and physical therapists though a few dentists and podiatrists offer the service.
Low-level laser therapy (LLLT) uses a class I, II, or III “red beam or near infrared nonthermal lasers with a wavelength between 600 and 1000 nanometers and from 5 to 500 milliwatts (mW).”
On the other hand, high-intensity laser therapy (HILT) utilizes a more powerful Class IV laser that produces 40,000 mW, or 40 W, of power and is supposedly able to penetrate deeper into the tissue. Their use is sometimes referred to as Deep Laser Therapy. Surgical lasers are also powered around 40 W.
4. How is laser treatment measured?
This is a difficult question to answer and one of the reasons high quality data on low level laser therapy is lacking.
One article in the Annals of Biomedical Engineering puts it this way, “Response to low level laser therapy changes with wavelength, irradiance, time, pulses and maybe even coherence and polarization, the treatment should cover an adequate area of the pathology, and then there is a matter of how long to irradiate for.”
So, lot’s of options and thus difficult to develop specific protocols that can subsequently be validated.
Let’s break it down into familiar parts: Medicine and Dose
The “medicine” of low level laser therapy involves a combination of the specific wavelength, how much power is used over a certain area (W/cm2), whether or not the light is pulsed, the speckle pattern, and whether or not the light is polarized or nonpolarized (sunlight = nonpolarized, glare = polarized).
Laser therapy doses are calculated using the amount of energy (measured in Joules), the energy density (J/cm2), treatment time and frequency of treatment.
There’s a significant problem with some of these assumptions, however. For example, the World Association for Laser Therapy (WALT) offers treatment suggestions but the measurement for energy and energy density makes assumptions for the power density (that W/cm2 we mentioned earlier). It’s almost like ordering 5 cc’s of whatever’s available–it’s not specific enough.
In case you were wondering though, WALT recommends between 4-8 J/cm2 per point for a tennis elbow but might be several thousand Joules in total per treatment.
5. What evidence is there for cold lasers (low-level laser therapy) and high-intensity lasers?
Let’s see what old Mr. Cochrane has to say…
A 2005 meta-analysis of 222 patients with rheumatoid arthritis reported that those treated with a cold laser (LLLT, class I-III) were able to reduce morning stiffness by 27 minutes as well as reducing pain by 1 point on the visual analog scale (the classic 0-10 pain scale). The major flaw of this analysis (or rather the trials within it) was that there was no single treatment protocol or consensus on the type of laser used.
One meta-analysis published in the BMJ went as far as to report the specifics of treatment and found that “LLLT reduces pain and disability in knee osteoarthritis at 4–8 J with 785–860 nm wavelength and at 1–3 J with 904 nm wavelength per treatment spot.”
Regarding HILT, a 2019 meta-analysis determined that although the quality of available evidence was “very low to low“, patients with back pain treated with HILT generally did better than those treated with sham lasers or conventional therapies alone. Similar findings were reported here and here.
6. Does insurance cover low-level laser therapy?
Basically, no, and it can get expensive.
Aetna considers LLLT for oral mucositis associated with cancer treatment to be medically necessary while it’s deemed experimental for all other uses. Cold laser therapy, is purported to treat everything from Alzheimer’s and obesity to soft tissue injuries and chronic pain.
In a policy brief justifying their lack of coverage for low level laser therapy, a Blue Cross/Blue Shield affiliate writes “The exact mechanism of its effect on tissue healing is unknown; hypotheses have included improved cellular repair and stimulation of the immune, lymphatic, and vascular systems.”
And the cost adds up. One New Jersey podiatrist treats her patients “two to three times a week for six to 10 sessions” for soft tissue injuries. Treatment sessions typically cost between $50 and $100. On the bright side, there are essentially no side effects of cold laser therapy.
While already a well-established part of surgical and aesthetic practice, there is still much we don’t know about the use of lasers in medicine, especially low-level laser therapy. If treatment protocols can be developed with clear targets, then clinical trials could validate their use for specific conditions. Until then, we must cautiously interpret available evidence and be wary of anecdote.
This post was medically reviewed by Joni Collins DMS, PA-C, CAC
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