Low-level laser therapy (LLLT) is a form of alternative medicine that applies low-level (low-power) lasers or light-emitting diodes (LEDs) to the surface or orifices of the body. Whereas "high-power" lasers are used in laser medicine to cut or destroy tissue, low-power lasers are claimed to relieve pain or to stimulate and enhance cell function.

The effects of LLLT appear to be limited to a specified set of wavelengths of laser,[1] and administering LLLT below the dose range does not appear to be effective.[2]

Despite a lack of consensus over its validity, some studies suggest that LLLT may be modestly effective, but in most cases no better than placebo, in relieving short-term pain for rheumatoid arthritis,[3] osteoarthritis,[4] acute and chronic neck pain,[5]tendinopathy,[1][6] and possibly chronic joint disorders.[2] The evidence for LLLT being useful in the treatment of low back pain,[7][8]dentistry[9][10] and wound healing is unclear.[11]

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Names

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Variations of LLLT have gone by a variety of alternate names including low-power laser therapy (LPLT), soft laser therapy, low-intensity laser therapy, low-energy laser therapy, cold laser therapy, bio-stimulation laser therapy, photobiomodulation,[12] photo-biotherapy, therapeutic laser, and monochromatic infrared light energy (MIRE) therapy.[13] When LLLT is administered to so-called "acupuncture points", the procedure may be called laser acupuncture. When applied to the head, LLLT may be known as transcranial photobiomodulation, transcranial near-infrared laser therapy (NILT) ,[14] or transcranial low level light therapy.

 

Medical uses

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Various LLLT devices have been promoted for use in treatment of several musculoskeletal conditions including carpal tunnel syndrome (CTS), fibromyalgia, osteoarthritis, andrheumatoid arthritis. They have also been promoted for temporomandibular joint (TMJ) disorders, wound healing, smoking cessation, and tuberculosis. While these treatments may briefly help some people with pain management, evidence does not support claims that they change long term outcomes, or that they work better than other, low tech ways of applying heat.[15]

The Centers for Medicare and Medicaid Services,[16] Aetna,[17] and Cigna[18] have reviewed the clinical evidence with respect to LLLT and found it insufficient to determine that LLLT is safe or effective for any purpose.

Mechanism[edit]

It is unclear how LLLT might work.[1] The effects of LLLT appear to be limited to a specified set of wavelengths of laser,[1] and administering LLLT below the dose range does not appear to be effective.[2] Photochemical reactions are well known in biological research; it may be that the light applied in low level laser therapy might react with the respiratory enzyme cytochrome c oxidase which is involved in the electron transport chain in mitochondria.[12][19]

 

History

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Hungarian physician and surgeon Endre Mester (1903-1984) is credited with the discovery of the biological effects of low power lasers,[20] which occurred a few years after the 1960 invention of the ruby laser and the 1961 invention of the helium–neon (HeNe) laser.[12] Mester accidentally discovered that low-level ruby laser light could regrow hair during an attempt to replicate an experiment that showed that such lasers could reduce tumors in mice. The laser he was using was faulty and wasn't as powerful as he thought; it failed to affect the tumors but he noticed that in the places where he had shaved the mice in order to do the experiments, the hair grew back faster on mice he treated compared with the placebos.[21] He published those results in 1967.[12] He went on to show that low level HeNe light could accelerate wound healing in mice.[12] By the 1970s he was applying low level laser light to treat people with skin ulcers.[12] In 1974 he founded the Laser Research Center at the Semmelweis Medical University in Budapest, and continued working there for the remainder of his life.[22] His sons carried on his work and brought it to the United States.[20]

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By 1987 companies selling lasers were claiming that they could treat pain, accelerate healing of sports injuries, and treat arthritis, but there was little evidence for this at that time.[20]By 2016 they had been marketed for wound healing, smoking cessation, tuberculosis, and musculoskeletal conditions such as temporomandibular joint disorders carpal tunnel syndrome, fibromyalgia, osteoarthritis, and rheumatoid arthritis, and there was still little evidence for these uses, other than a possible use in temporarily treating muscle or joint pain.[15] Mester originally called this approach "laser biostimulation'", but it soon became known as “low level laser therapy" and with the adaptation of light emitting diodes by those studying this approach, it became known as "low level light therapy", and to resolve confusion around the exact meaning of "low level", the term "photobiomodulation" arose.[21]

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Society and culture

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Reimbursement

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As of 2006, the Centers for Medicare and Medicaid Services did not provide coverage for LLLT,[16] as of 2014 Aetna did not provide coverage,[17] and as of 2016 Cigna did not provide coverage.[18]

Research

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Musculoskeletal

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A 2008 Cochrane Library review concluded that LLLT has insufficient evidence for treatment of nonspecific low back pain,[7] a finding echoed in a 2010 review of chronic low back pain.[8] A 2015 review found benefit in nonspecific chronic low-back pain.[23]

LLLT may be useful in the treatment of both acute and chronic neck pain.[5] In 2013, however, a systematic review and meta-analysis of LLLT for neck pain indicated that the benefit was not of significant importance and that the evidence had a high risk of bias.[24]

There are tentative data that LLLT is useful in the short-term treatment of pain caused by rheumatoid arthritis,[3] and possibly chronic joint disorders.[2] While it does not appear to improve pain in temporomandibular disorders, it may improve function.[25] Evidence for usefulness in osteoarthritis is poor.[4][26]

There is tentative evidence of benefit in tendinopathy.[1][6] A 2015 review found benefit in shoulder tendinopathy.[27] A 2014 Cochrane review found tentative evidence that it may help in frozen shoulders.[28]

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Evidence does not support a benefit in delayed-onset muscle soreness.[29] It may be useful for muscle pain and injuries.[30]

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Mouth

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Similarly, the use of lasers to treat chronic periodontitis[9] and to speed healing of infections around dental implants[10] is suggested, but there is insufficient evidence to indicate a use superior to traditional practices.[31] There is tentative evidence for dentin hypersensitivity.[32] It does not appear to be useful for orthodontic pain[33][34] LLLT might be useful for wisdom tooth extraction (complications)[35] and oral mucositis.[36]

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Hair loss

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LLLT has been studied as a treatment for hair loss; a review in 2012 found little evidence to support the use of lasers to treat hair loss.[37] A 2014 review found tentative evidence for benefit for lasers.[38] While another 2014 review concluded that the results are mixed, have a high risk of bias, and that its effectiveness is unclear.[39] A 2015 review also found tentative evidence of benefit.[40]

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Brain injuries

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LLLT has been studied for traumatic brain injury (TBI) and stroke among other conditions.[12] When applied to the head it is known as transcranial photobiomodulation or transcranial low level light therapy.

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Cancer

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LLLT has been studied as a way to reduce pain and swelling in breast-cancer related lymphedema.[41][11] Stephen Barrett, writing for Quackwatch, concluded in 2009 there was evidence to support LLLT use for temporary pain relief, but "there's no reason to believe that they will influence the course of any ailment or are more effective than other forms of heat delivery."[42] Barrett's position was unchanged as of 2016.[15]

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Stem cells

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An ongoing area of research is the application of LLLT for increasing cell proliferation, including stem cells.[43]

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Veterinary use

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Veterinary clinics use cold laser devices to treat a wide variety of ailments, from arthritis to wounds, on dogs and cats.[44][45] Very little research has been done on the effects of this treatment on animals. Currently, laser therapy equipment is aggressively marketed to veterinarians as a supposedly powerful therapeutic tool and revenue generator. Brennen McKenzie, president of the Evidence-Based Veterinary Medical Association, has stated that "research into cold laser in dogs and cats is sparse and generally low quality. Most studies are small and have minimal or uncertain controls for bias and error".[46][47] While allowing that some studies show promising results, he reports that others do not. While believing that there is enough evidence to warrant further study, he concludes that there is not enough evidence to support routine clinical use of cold laser in animals.

If vets want to try this therapy, they have an obligation to be clear with client that the risks and benefits have not been established and that the treatment is essentially experimental. There is nothing wrong with such a treatment given appropriate informed consent, but the aggressive marketing of laser equipment to vets as a profitable treatment is ethically questionable given the lack of good evidence that it is a truly safe and effective treatment for any condition.[48]

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Light therapy—or phototherapy, classically referred to as heliotherapy—consists of exposure to daylight or to specific wavelengthsof light using polychromatic polarised light, lasers, light-emitting diodes, fluorescent lamps, dichroic lamps or very bright, full-spectrum light. The light is administered for a prescribed amount of time and, in some cases, at a specific time of day.

One common use of the term is associated with the treatment of skin disorders, chiefly psoriasis, acne vulgaris, eczema and neonatal jaundice.[citation needed]

Light therapy which strikes the retina of the eyes is used to treat diabetic retinopathy and also circadian rhythm disorders such asdelayed sleep phase disorder and can also be used to treat seasonal affective disorder, with some support for its use also with non-seasonal psychiatric disorders.

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Medical uses

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Skin conditions

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The treatments involve exposing the skin to ultraviolet light. The exposures can be to small area of the skin or over the whole body surface, like in a tanning bed. The most common treatment is with narrowband UVB (NB-UVB) with a wavelength of 311–313 nanometer. It was found that this is the safest treatment.[1] Full body phototherapy can be delivered at a doctor's office or at home using a large high power UVB booth.[2]

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Atopic dermatitis

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Light therapy is considered one of the best monotherapy treatments for atopic dermatitis (AD), when applied to patients who have not responded to traditional topical treatments. The therapy offers a wide range of options: UVA1 for acute AD, NB-UVB for chronic AD, and balneophototherapy have proven their efficacy over the recent past. Patients tolerate the therapy safely but, as in any therapy, there are adverse effects and care should be taken in its application, particularly to children.[3]

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Psoriasis

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See also: Goeckerman therapy

For psoriasis, UVB phototherapy has been shown to be effective.[4] A feature of psoriasis is localized inflammation mediated by the immune system.[5] Ultraviolet radiation is known to suppress the immune system and reduce inflammatory responses. Light therapy for skin conditions like psoriasis usually use NB-UVB (311 nm wavelength) though it may use UV-A (315–400 nm wavelength) or UV-B (280–315 nm wavelength) light waves. UV-A, combined with psoralen, a drug taken orally, is known as PUVA treatment. In UVB phototherapy the exposure time is very short, seconds to minutes depending on intensity of lamps and the person's skin pigment and sensitivity. The time is controlled with a timer that turns off the lamps after the treatment time ends.

 

Vitiligo

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One percent of the population suffer from vitiligo, and narrowband UVB phototherapy is an effective treatment. "NB-UVB phototherapy results in satisfactory repigmentation in our vitiligo patients and should be offered as a treatment option."[6]

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Acne vulgaris

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Evidence for light therapy and lasers in acne vulgaris as of 2012 is not sufficient to recommend them.[7] There is moderate evidence for the efficacy of blue and blue-red light therapies in treating mild acne, but most studies are of low quality.[8][9] While light therapy appears to provide short term benefit, there is a lack of long term outcome data or data in those with severe acne.[10]

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Cancer

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According to the American Cancer Society, there is some evidence that ultraviolet light therapy may be effective in helping treat certain kinds of skin cancer, and ultraviolet blood irradiation therapy is established for this application. However, alternative uses of light for cancer treatment – light box therapy and colored light therapy – are not supported by evidence.[11] Photodynamic therapy (often with red light) is used to treat certain superficial non-melanoma skin cancers.[12]

 

Other skin conditions

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Phototherapy can be effective in the treatment of eczema, atopic dermatitis, polymorphous light eruption, cutaneous T-cell lymphoma[13] and lichen planus. Narrowband UVB lamps, 311–313 nanometer is the most common treatment.[14]

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Wound healing

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Low level laser therapy has been studied as a potential treatment for chronic wounds.[15] Reviews of the scientific literature do not support the widespread use of this technique due to inconsistent results and low research quality.[15][16] Higher power lasers have also been used to close acute wounds as an alternative to stitching.[15]

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Retinal conditions

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There is preliminary evidence that light therapy is an effective treatment for diabetic retinopathy and diabetic macular oedema.[17][18]

 

Mood and sleep related

 

Seasonal affective disorder

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Main article: Seasonal affective disorder

The effectiveness of light therapy for treating SAD may be linked to the fact that light therapy makes up for lost sunlight exposure and resets the body's internal clock.[19] Studies show that light therapy helps reduce the debilitating and depressive behaviors of SAD, such as excessive sleepiness and fatigue, with results lasting for at least 1 month. Light therapy is preferred over antidepressants in the treatment of SAD because it is a relatively safe and easy therapy.[20]

It is possible that response to light therapy for SAD could be season dependent.[21] Morning therapy has provided the best results because light in the early morning aids in regulating the circadian rhythm.[20]

A 2007 systematic review by the Swedish agency SBU found insufficient evidence that light therapy was able to alleviate symptoms of depression or seasonal affective disorder.[22]The report recommended that: "Approximately 100 participants are required to establish whether the therapy is moderately more effective than placebo".[22] Although treatment in light therapy rooms was well established in Sweden, no satisfactory, controlled studies had been published on the subject.[22] This led to the closure of a number of clinics offering light therapy in Sweden.[23]

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Non-seasonal depression

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Light therapy has also been suggested in the treatment of non-seasonal depression and other psychiatric mood disturbances, including major depressive disorder,[24] bipolar disorder and postpartum depression.[25][26] A meta-analysis by the Cochrane Collaboration concluded that "for patients suffering from non-seasonal depression, light therapy offers modest though promising antidepressive efficacy."[27] A 2008 systematic review concluded that "overall, bright light therapy is an excellent candidate for inclusion into the therapeutic inventory available for the treatment of nonseasonal depression today, as adjuvant therapy to antidepressant medication, or eventually as stand-alone treatment for specific subgroups of depressed patients."[28] A 2015 review found that supporting evidence for light therapy was limited due to serious methodological flaws.[29]

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Circadian rhythm sleep disorders and jet lag

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Main article: Circadian rhythm sleep disorder

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Chronic circadian rhythm sleep disorders (CRSD)

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In the management of circadian rhythm disorders such as delayed sleep phase disorder (DSPD), the timing of light exposure is critical. Light exposure administered to the eyes before or after the nadir of the core body temperature rhythm can affect the phase response curve.[30] Use upon awakening may also be effective for non-24-hour sleep–wake disorder.[31] Some users have reported success with lights that turn on shortly before awakening (dawn simulation). Evening use is recommended for people with advanced sleep phase disorder. Some, but not all, totally blind people whose retinae are intact, may benefit from light therapy.

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Situational CRSD

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Light therapy has been tested for individuals with shift work sleep disorder,[32] and for jet lag.[33]

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Sleep disorder in Parkinson's disease

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Light therapy has been trialed in treating sleep disorders experienced by patients with Parkinson's disease.[34]

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Neonatal jaundice (Postnatal Jaundice)

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Further information: Neonatal jaundice

Light therapy is used to treat cases of neonatal jaundice[35] through the isomerization of the bilirubin and consequently transformation into compounds that the newborn can excrete via urine and stools. A common treatment of neonatal jaundice is the bili light or billiblanket.

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Techniques

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Photodynamic therapy

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Main article: Photodynamic therapy

Photodynamic therapy is a form of phototherapy using nontoxic light-sensitive compounds that are exposed selectively to light, whereupon they become toxic to targeted malignant and other diseased cells

One of the treatments is using blue light with aminolevulinic acid for the treatment of actinic keratosis. This is not a U.S. FDA-approved treatment for acne vulgaris.[36]

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Light boxes

 

The brightness and color temperature of light from a light box are quite similar to daylight.

"Light box" redirects here. For other uses, see Lightbox (disambiguation).

The production of the hormone melatonin, a sleep regulator, is inhibited by light and permitted by darkness as registered by photosensitive ganglion cells in the retina. To some degree, the reverse is true for serotonin[citation needed], which has been linked to mood disorders. Hence, for the purpose of manipulating melatonin levels or timing, light boxes providing very specific types of artificial illumination to the retina of the eye are effective.[citation needed]

Light therapy uses either a light box which emits up to 10,000 lux of light at a specified distance, much brighter than a customary lamp, or a lower intensity of specific wavelengths of light from the blue (460 nm) to the green (525 nm) areas of the visible spectrum.[37] A 1995 study showed that green light therapy at doses of 350 lux produces melatonin suppression and phase shifts equivalent to 10,000 lux white light therapy,[38][39] but another study published in May 2010 suggests that the blue light often used for SAD treatment should perhaps be replaced by green or white illumination, because of a possible involvement of the cones in melatonin suppression.[40]

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In treatment, the patient's eyes are to be at a prescribed distance from the light source with the light striking the (lower) retina. This does not require looking directly into the light.

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Considering three major factors – clinical efficacy, ocular and dermatologic safety, and visual comfort, the Center for Environmental Therapeutics (CET) recommends the following criteria for light box selection:[41]

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• Light boxes should have been tested successfully in peer-reviewed clinical trials.

• The box should provide 10,000 lux of illumination at a comfortable sitting distance. Product specifications are often missing or unverified; illuminance can be controlled using alight meter.

• Fluorescent lamps should have a smooth diffusing screen that filters out ultraviolet (UV) rays. UV rays are harmful to the eyes and skin.

• Blue light is known to be superior to red light in managing depressive symptoms which have a seasonal pattern.[42]

• The light should be projected downward toward the eyes at an angle to minimize aversive visual glare.

• Smaller is not better; when using a compact light box, even small head movements will take the eyes out of the therapeutic range of the light.

 

Risks and complications

 

Ultraviolet

 

Ultraviolet light causes progressive damage to human skin and erythema even from small doses.[43][44] This is mediated by genetic damage, collagen damage, as well as destruction of vitamin A and vitamin C in the skin and free radical generation.[citation needed] Ultraviolet light is also known to be a factor in formation of cataracts.[45][46] Ultraviolet radiation exposure is strongly linked to incidence of skin cancer.[47][43][48]

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Visible light

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Optical radiation of any kind with enough intensity can cause damage to the eyes and skin including photoconjunctivitis and photokeratitis.[49] Researchers have questioned whether limiting blue light exposure could reduce the risk of age-related macular degeneration.[50] It is reported that bright light therapy may activate the production of reproductive hormones, such as testosterone, luteinizing hormone, follicle-stimulating hormone, and estradiol.[51][52]

Modern phototherapy lamps used in the treatment of seasonal affective disorder and sleep disorders either filter out or do not emit ultraviolet light and are considered safe and effective for the intended purpose, as long as photosensitizing drugs are not being taken at the same time and in the absence of any existing eye conditions. Light therapy is a mood altering treatment, and just as with drug treatments, there is a possibility of triggering a manic state from a depressive state, causing anxiety and other side effects. While these side effects are usually controllable, it is recommended that patients undertake light therapy under the supervision of an experienced clinician, rather than attempting to self-medicate.[53]

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Contraindications to light therapy for seasonal affective disorder include conditions that might render the eyes more vulnerable to phototoxicity, tendency toward mania, photosensitive skin conditions, or use of a photosensitizing herb (such as St. John's wort) or medication.[54][55] Patients with porphyria should avoid most forms of light therapy. Patients on certain drugs such as methotrexate or chloroquine should use caution with light therapy as there is a chance that these drugs could cause porphyria.[citation needed]

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Side effects of light therapy for sleep phase disorders include jumpiness or jitteriness, headache, eye irritation and nausea.[56] Some non-depressive physical complaints, such as poor vision and skin rash or irritation, may improve with light therapy.[57]

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History

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Many ancient cultures practiced various forms of heliotherapy, including people of Ancient Greece, Ancient Egypt, and Ancient Rome.[58] The Inca, Assyrian and early Germansettlers also worshipped the sun as a health bringing deity. Indian medical literature dating to 1500 BCE describes a treatment combining herbs with natural sunlight to treat non-pigmented skin areas. Buddhist literature from about 200 CE and 10th-century Chinese documents make similar references.

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The Faroese physician Niels Finsen is believed to be the father of modern phototherapy. He developed the first artificial light source for this purpose.[citation needed] Finsen used short wavelength light to treat lupus vulgaris, a skin infection caused by Mycobacterium tuberculosis. He thought that the beneficial effect was due to ultraviolet light killing the bacteria, but recent studies showed that his lens and filter system did not allow such short wavelengths to pass through, leading instead to the conclusion that light of approximately 400 nanometers generated reactive oxygen that would kill the bacteria.[59] Finsen also used red light to treat smallpox lesions. He received the Nobel Prize in Physiology or Medicine in 1903.[60] Scientific evidence for some of his treatments is lacking, and later eradication of smallpox and development of antibiotics for tuberculosis rendered light therapy obsolete for these diseases.[61]

From the late nineteenth century until the early 1930s, light therapy was considered an effective and mainstream medical therapy in the UK for conditions such as varicose ulcer, 'sickly children' and a wide range of other conditions. Controlled trials by the medical scientist Dora Colebrook supported by the Medical Research Council, indicated that light therapy was not effective for such a wide range of conditions.[62]

Since then a large array of treatments using controlled light have been developed. Though the popular consumer understanding of "light therapy" is associated with treating seasonal affective disorder, circadian rhythm disorders and skin conditions like psoriasis, other applications include the use of low level laser, red light, near-infrared and ultraviolet lights forpain management, hair growth,[citation needed] skin treatments,[which?] and accelerated wound healing.[citation needed]

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