Light therapy
Encyclopedia
Light therapy or phototherapy (classically referred to as heliotherapy) consists of exposure to daylight or to specific wavelengths of light using laser
s, light-emitting diode
s, fluorescent lamp
s, dichroic lamps or very bright, full-spectrum light, usually controlled with various devices. The light is administered for a prescribed amount of time and, in some cases, at a specific time of day.
Common use of the term is associated with the treatment of skin disorders (chiefly psoriasis
), sleep disorder and some psychiatric disorders. Light therapy directed at the skin is also used to treat acne vulgaris
, eczema
and neonatal jaundice
. Light therapy which strikes the retina
of the eyes is used to treat circadian rhythm
disorders such as delayed sleep phase syndrome
and can also be used to treat seasonal affective disorder
, with some support for its use also with non-seasonal psychiatric disorders.
Other medical applications of light therapy also include pain management
, accelerated wound healing
, hair growth, improvement in blood properties and blood circulation, and sinus
-related diseases and disorders. Many of these use low level laser therapy
and red light therapy in the 620–660 nm range.
, ancient egypt
, and ancient Rome
. The Inca, Assyrian
and early German settlers also worshipped the sun as a health bringing deity. Indian medical literature dating to 1500 BC describes a treatment combining herbs with natural sunlight to treat non-pigmented skin areas. Buddhist literature from about 200 AD and 10th-century Chinese documents made similar references.
Faroese physician Niels Finsen
is believed to be the father of modern phototherapy. He developed the first artificial light source for this purpose, and used his invention to treat lupus vulgaris
. He received the Nobel Prize in Physiology or Medicine
in 1903.
Since then a large array of treatments have been developed from the use of controlled light. Though the popular consumer understanding of "light therapy" is associated with treating seasonal affective disorder
and skin conditions like psoriasis
, other applications include the application of low level laser
, red light
, near-infrared
and ultraviolet
lights for pain management
, hair growth, skin treatments, accelerated wound healing.
A feature of psoriasis is localized inflammation mediated by the immune system
. Ultraviolet
radiation is known to suppress the immune system and reduce inflammatory responses. Light therapy for skin conditions like psoriasis use UV-A (315–400 nm wavelength) or UV-B (280–315 nm wavelength) light waves. UV-A, combined with a drug taken orally, is known as PUVA
treatment.
It was found that some of the visible violet light present in sunlight (in the range 415–430 nm) activates a porphyrin
(Coproporphyrin III) in Propionibacterium acnes
which damages and ultimately kills the bacteria by releasing singlet oxygen. A total of 320 J/cm2
of light within this range renders the bacteria non-viable.
Since there are few porphyrins naturally found in the skin, the treatment is believed safe except in patients with porphyria
; although eye protection is used due to light-sensitive chemicals in the retina. The light is usually created by superluminous LED
s. This form of treatment has been approved by the FDA for some lightwave systems .
Overall improvements of on average 76% for 80% of patients occurs over three months; most studies show that it performs better than benzoyl peroxide
and the treatment is far better tolerated. However, approximately 10% of users see no improvement.
, Atopic Dermatitis
, Polymorphous light eruption
, Vitiligo
, Lichen Planus
and Mycosis Fungoides
.
radiation: UV-A and UV-B.
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.
s in the retina. To some degree, the reverse is true for serotonin
, 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.
Light therapy either uses a lightbox which emits up to 10,000 lux
of light, much brighter than a customary incandescent lamp, or a lower intensity of specific wavelengths of light from the blue (470 nm) to the green (525 nm) areas of the visible spectrum
. Newer light therapy devices use LED technology, making them much smaller and more convenient for users. 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, 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.
In treatment, the patient's eyes are to be at a prescribed distance from the light source with the light striking the retina. This does not require looking directly into the light.
Considering three major factors - clinical efficacy, ocular and dermatologic safety, and visual comfort - CET recommends the following criteria for light box selection:
is preferred for seasonal affective disorder
(SAD), light boxes may be effective for the treatment of the condition. Light boxes for seasonal affective disorder are designed to filter out most UV light, which can cause eye and skin damage. The U.S. Food and Drug Administration has not approved the use of light boxes to treat SAD due to unclear results in clinical trial
s, but light therapy is still seen as the main form of treatment for SAD. Direct sunlight, reflected into the windows of a home or office by a computer-controlled mirror device called a heliostat
, has also been used as a type of light therapy for the treatment of SAD.
It is possible that response to light therapy for SAD could be season dependent.
and postpartum depression
. A meta-analysis by the Cochrane Collaboration
concluded that "For patients suffering from non-seasonal depression, light therapy offers modest though promising antidepressive efficacy."
disorders such as delayed sleep phase syndrome
(DSPS), the timing of light exposure is critical. For DSPS, the light must be provided to the retina as soon after spontaneous awakening as possible to achieve the desired effect, as shown by the phase response curve
for light in humans. Some users have reported success with lights that turn on shortly before awakening (dawn simulation
). Morning use may also be effective for non-24-hour sleep-wake syndrome
, while evening use is recommended for advanced sleep phase syndrome
.
, and for jet lag
.
Light therapy is used to treat cases of neonatal jaundice
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
.
by reducing patients' tremors.
light causes progressive damage to human skin. 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. Ultraviolet light is also known to be a factor in formation of cataract
s. Researchers have questioned whether limiting blue light exposure could reduce the risk of age-related macular degeneration.
Modern phototherapy lamps used in the treatment of seasonal affective disorder and sleep disorder
s 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.
It is reported that bright light therapy may activate the production of reproductive hormones, such as testosterone
, luteinizing hormone
, follicle-stimulating hormone
, and estradiol
.
There are few absolute contraindications to light therapy, although there are some circumstances in which caution is required. These include when a patient has a condition that might render his or her eyes more vulnerable to phototoxicity, has a tendency toward mania, has a photosensitive skin condition, or is taking a photosensitizing herb (such as St. John's wort) or medication. Patients with porphyria
should avoid most forms of light therapy. Patients on certain drugs like methotrexate
or chloroquine
should use caution with light therapy as there is a chance that these drugs could cause porphyria.
Laser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of photons. The term "laser" originated as an acronym for Light Amplification by Stimulated Emission of Radiation...
s, light-emitting diode
Light-emitting diode
A light-emitting diode is a semiconductor light source. LEDs are used as indicator lamps in many devices and are increasingly used for other lighting...
s, fluorescent lamp
Fluorescent lamp
A fluorescent lamp or fluorescent tube is a gas-discharge lamp that uses electricity to excite mercury vapor. The excited mercury atoms produce short-wave ultraviolet light that then causes a phosphor to fluoresce, producing visible light. A fluorescent lamp converts electrical power into useful...
s, dichroic lamps or very bright, full-spectrum light, usually controlled with various devices. The light is administered for a prescribed amount of time and, in some cases, at a specific time of day.
Common use of the term is associated with the treatment of skin disorders (chiefly psoriasis
Psoriasis
Psoriasis is an autoimmune disease that appears on the skin. It occurs when the immune system mistakes the skin cells as a pathogen, and sends out faulty signals that speed up the growth cycle of skin cells. Psoriasis is not contagious. However, psoriasis has been linked to an increased risk of...
), sleep disorder and some psychiatric disorders. Light therapy directed at the skin is also used to treat acne vulgaris
Acne vulgaris
Acne vulgaris is a common human skin disease, characterized by areas of skin with seborrhea , comedones , papules , pustules , Nodules and possibly scarring...
, eczema
Eczema
Eczema is a form of dermatitis, or inflammation of the epidermis . In England, an estimated 5.7 million or about one in every nine people have been diagnosed with the disease by a clinician at some point in their lives.The term eczema is broadly applied to a range of persistent skin conditions...
and neonatal jaundice
Neonatal jaundice
Neonatal jaundice or Neonatal hyperbilirubinemia is a yellowing of the skin and other tissues of a newborn infant. A bilirubin level of more than 85 umol/l manifests clinical jaundice in neonates whereas in adults a level of 34 umol/l would look icteric...
. Light therapy which strikes the retina
Retina
The vertebrate retina is a light-sensitive tissue lining the inner surface of the eye. The optics of the eye create an image of the visual world on the retina, which serves much the same function as the film in a camera. Light striking the retina initiates a cascade of chemical and electrical...
of the eyes is used to treat circadian rhythm
Circadian rhythm
A circadian rhythm, popularly referred to as body clock, is an endogenously driven , roughly 24-hour cycle in biochemical, physiological, or behavioural processes. Circadian rhythms have been widely observed in plants, animals, fungi and cyanobacteria...
disorders such as delayed sleep phase syndrome
Delayed sleep phase syndrome
Delayed sleep-phase syndrome , also known as delayed sleep-phase disorder or delayed sleep-phase type , is a circadian rhythm sleep disorder, a chronic disorder of the timing of sleep, peak period of alertness, the core body temperature rhythm, hormonal and other daily rhythms, compared to the...
and can also be used to treat seasonal affective disorder
Seasonal affective disorder
Seasonal affective disorder , also known as winter depression, winter blues, summer depression, summer blues, or seasonal depression, is a mood disorder in which people who have normal mental health throughout most of the year experience depressive symptoms in the winter or summer, spring or autumn...
, with some support for its use also with non-seasonal psychiatric disorders.
Other medical applications of light therapy also include pain management
Pain management
Pain management is a branch of medicine employing an interdisciplinary approach for easing the suffering and improving the quality of life of those living with pain. The typical pain management team includes medical practitioners, clinical psychologists, physiotherapists, occupational therapists,...
, accelerated wound healing
Wound healing
Wound healing, or cicatrisation, is an intricate process in which the skin repairs itself after injury. In normal skin, the epidermis and dermis exists in a steady-state equilibrium, forming a protective barrier against the external environment...
, hair growth, improvement in blood properties and blood circulation, and sinus
Sinus
- Anatomy :In anatomy, where a sinus is a sac or cavity in any organ or tissue:*Sinus , description of the general term*Paranasal sinuses, air cavities in the cranial bones, especially those near the nose, including:...
-related diseases and disorders. Many of these use low level laser therapy
Low level laser therapy
Low-level laser therapy is a medical and veterinary treatment that uses low-level lasers or light-emitting diodes to alter cellular function...
and red light therapy in the 620–660 nm range.
History
Many ancient cultures practiced various forms of heliotherapy, including people of the Ancient GreeceAncient Greece
Ancient Greece is a civilization belonging to a period of Greek history that lasted from the Archaic period of the 8th to 6th centuries BC to the end of antiquity. Immediately following this period was the beginning of the Early Middle Ages and the Byzantine era. Included in Ancient Greece is the...
, ancient egypt
Ancient Egypt
Ancient Egypt was an ancient civilization of Northeastern Africa, concentrated along the lower reaches of the Nile River in what is now the modern country of Egypt. Egyptian civilization coalesced around 3150 BC with the political unification of Upper and Lower Egypt under the first pharaoh...
, and ancient Rome
Ancient Rome
Ancient Rome was a thriving civilization that grew on the Italian Peninsula as early as the 8th century BC. Located along the Mediterranean Sea and centered on the city of Rome, it expanded to one of the largest empires in the ancient world....
. The Inca, Assyrian
Assyria
Assyria was a Semitic Akkadian kingdom, extant as a nation state from the mid–23rd century BC to 608 BC centred on the Upper Tigris river, in northern Mesopotamia , that came to rule regional empires a number of times through history. It was named for its original capital, the ancient city of Assur...
and early German settlers also worshipped the sun as a health bringing deity. Indian medical literature dating to 1500 BC describes a treatment combining herbs with natural sunlight to treat non-pigmented skin areas. Buddhist literature from about 200 AD and 10th-century Chinese documents made similar references.
Faroese physician Niels Finsen
Niels Ryberg Finsen
Niels Ryberg Finsen was a Faroese-Danish physician and scientist of Icelandic descent. He was awarded the Nobel Prize in Medicine and Physiology in 1903 "in recognition of his contribution to the treatment of diseases, especially lupus vulgaris, with concentrated light radiation, whereby he has...
is believed to be the father of modern phototherapy. He developed the first artificial light source for this purpose, and used his invention to treat lupus vulgaris
Lupus vulgaris
Lupus vulgaris are painful cutaneous tuberculosis skin lesions with nodular appearance, most often on the face around nose, eyelids, lips, cheeks and ears. The lesions may ultimately develop into disfiguring skin ulcers if left untreated...
. He received the Nobel Prize in Physiology or Medicine
Nobel Prize in Physiology or Medicine
The Nobel Prize in Physiology or Medicine administered by the Nobel Foundation, is awarded once a year for outstanding discoveries in the field of life science and medicine. It is one of five Nobel Prizes established in 1895 by Swedish chemist Alfred Nobel, the inventor of dynamite, in his will...
in 1903.
Since then a large array of treatments have been developed from the use of controlled light. Though the popular consumer understanding of "light therapy" is associated with treating seasonal affective disorder
Seasonal affective disorder
Seasonal affective disorder , also known as winter depression, winter blues, summer depression, summer blues, or seasonal depression, is a mood disorder in which people who have normal mental health throughout most of the year experience depressive symptoms in the winter or summer, spring or autumn...
and skin conditions like psoriasis
Psoriasis
Psoriasis is an autoimmune disease that appears on the skin. It occurs when the immune system mistakes the skin cells as a pathogen, and sends out faulty signals that speed up the growth cycle of skin cells. Psoriasis is not contagious. However, psoriasis has been linked to an increased risk of...
, other applications include the application of low level laser
Low level laser therapy
Low-level laser therapy is a medical and veterinary treatment that uses low-level lasers or light-emitting diodes to alter cellular function...
, red light
Red light
Red light may refer to:Films:* Red Light, a 1949 crime film starring George Raft* Redlight, a 2009 documentary of the Redlight Children Campaign* Red Lights , a 2004 French film, also known as Feux rouges...
, near-infrared
Infrared
Infrared light is electromagnetic radiation with a wavelength longer than that of visible light, measured from the nominal edge of visible red light at 0.74 micrometres , and extending conventionally to 300 µm...
and ultraviolet
Ultraviolet
Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...
lights for pain management
Pain management
Pain management is a branch of medicine employing an interdisciplinary approach for easing the suffering and improving the quality of life of those living with pain. The typical pain management team includes medical practitioners, clinical psychologists, physiotherapists, occupational therapists,...
, hair growth, skin treatments, accelerated wound healing.
Psoriasis
Three percent of the population suffer from psoriasis, and UVB phototherapy has been shown to effectively treat the disease.A feature of psoriasis is localized inflammation mediated by the immune system
Immune system
An immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own...
. Ultraviolet
Ultraviolet
Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...
radiation is known to suppress the immune system and reduce inflammatory responses. Light therapy for skin conditions like psoriasis use UV-A (315–400 nm wavelength) or UV-B (280–315 nm wavelength) light waves. UV-A, combined with a drug taken orally, is known as PUVA
PUVA
PUVA is a psoralen + UVA treatment for eczema, psoriasis, graft-versus-host disease and vitiligo, and mycosis fungoides. The psoralen is applied or taken orally to sensitize the skin, then the skin is exposed to UVA. Long term use has been associated with higher rates of skin cancer.Psoralens are...
treatment.
Acne vulgaris
Sunlight was long known to improve acne, and this was thought to be due to antibacterial and other effects of the ultraviolet spectrum which cannot be used as a long-term treatment due to the likelihood of skin damage.It was found that some of the visible violet light present in sunlight (in the range 415–430 nm) activates a porphyrin
Porphyrin
Porphyrins are a group of organic compounds, many naturally occurring. One of the best-known porphyrins is heme, the pigment in red blood cells; heme is a cofactor of the protein hemoglobin. Porphyrins are heterocyclic macrocycles composed of four modified pyrrole subunits interconnected at...
(Coproporphyrin III) in Propionibacterium acnes
Propionibacterium acnes
Propionibacterium acnes is a relatively slow growing, typically aerotolerant anaerobic gram positive bacterium that is linked to the skin condition acne; it can also cause chronic blepharitis and endophthalmitis, the latter particularly following intraocular surgery...
which damages and ultimately kills the bacteria by releasing singlet oxygen. A total of 320 J/cm2
Fluence
In physics, fluence is the flux integrated over time. For particles, it is defined as the total number of particles that intersect a unit area in a specific time interval of interest, and has units of m–2...
of light within this range renders the bacteria non-viable.
Since there are few porphyrins naturally found in the skin, the treatment is believed safe except in patients with porphyria
Porphyria
Porphyrias are a group of inherited or acquired disorders of certain enzymes in the heme bio-synthetic pathway . They are broadly classified as acute porphyrias and cutaneous porphyrias, based on the site of the overproduction and accumulation of the porphyrins...
; although eye protection is used due to light-sensitive chemicals in the retina. The light is usually created by superluminous LED
LEd
LEd is a TeX/LaTeX editing software working under Microsoft Windows. It is a freeware product....
s. This form of treatment has been approved by the FDA for some lightwave systems .
Overall improvements of on average 76% for 80% of patients occurs over three months; most studies show that it performs better than benzoyl peroxide
Benzoyl peroxide
Benzoyl peroxide is an organic compound in the peroxide family. It consists of two benzoyl groups bridged by a peroxide link. Its structural formula is [C6H5C]2O2. It is one of the most important organic peroxides in terms of applications and the scale of its production...
and the treatment is far better tolerated. However, approximately 10% of users see no improvement.
Other skin conditions
Phototherapy can be effective in the treatment of EczemaEczema
Eczema is a form of dermatitis, or inflammation of the epidermis . In England, an estimated 5.7 million or about one in every nine people have been diagnosed with the disease by a clinician at some point in their lives.The term eczema is broadly applied to a range of persistent skin conditions...
, Atopic Dermatitis
Atopic dermatitis
Atopic dermatitis is an inflammatory, chronically relapsing, non-contagious and pruritic skin disorder...
, Polymorphous light eruption
Polymorphous Light Eruption
Polymorphous light eruption , or polymorphic light eruption , is a skin condition caused by sunlight.- Types :Two subtypes have been described:*Juvenile spring eruption*Benign summer light eruption-Presentation:...
, Vitiligo
Vitiligo
Vitiligo is a condition that causes depigmentation of sections of skin. It occurs when melanocytes, the cells responsible for skin pigmentation, die or are unable to function. The cause of vitiligo is unknown, but research suggests that it may arise from autoimmune, genetic, oxidative stress,...
, Lichen Planus
Lichen planus
Lichen planus is a chronic mucocutaneous disease that affects the skin, tongue, and oral mucosa. The disease presents itself in the form of papules, lesions, or rashes. Lichen planus does not involve lichens, the fungus/algae symbionts that often grow on tree trunks; the name refers to the dry and...
and Mycosis Fungoides
Mycosis fungoides
-External links:* * *...
.
Tanning
Tanning is caused by the effects of two different spectrums of ultravioletUltraviolet
Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...
radiation: UV-A and UV-B.
Wound healing
Some case studies have found low-level laser light to be possibly helpful as an adjuctive treatment in wound healing, although a review of the overall scientific literature does not support the use of low-level laser therapy for this purpose.Photodynamic therapy
This treatment is based on a photo-sensitive liquid that is injected to the body. this liquid is attached to the unhealthy cells of the body. When it is exposed from outside to strong light it become solid, and thus it kills the unhealthy cells.One of the treatments is using blue light with aminolevulinic acid
Photodynamic therapy
Photodynamic therapy is used clinically to treat a wide range of medical conditions, including malignant cancers, and is recognised as a treatment strategy which is both minimally invasive and minimally toxic...
for the treatment of actinic keratosis
Actinic keratosis
Actinic keratosis is a premalignant condition of thick, scaly, or crusty patches of skin. It is more common in fair-skinned people. It is associated with those who are frequently exposed to the sun, as it is usually accompanied by solar damage...
. This is not a U.S. FDA-approved treatment for acne vulgaris.
Light boxes
The production of the hormone melatonin, a sleep regulator, is inhibited by light and permitted by darkness as registered by photosensitive ganglion cellPhotosensitive ganglion cell
Photosensitive ganglion cells, also called photosensitive Retinal Ganglion Cells , intrinsically photosensitive Retinal Ganglion Cells or melanopsin-containing ganglion cells, are a type of neuron in the retina of the mammalian eye.They were discovered in the early 1990sand are, unlike other...
s in the retina. To some degree, the reverse is true for serotonin
Serotonin
Serotonin or 5-hydroxytryptamine is a monoamine neurotransmitter. Biochemically derived from tryptophan, serotonin is primarily found in the gastrointestinal tract, platelets, and in the central nervous system of animals including humans...
, which has been linked to mood disorders. Hence, for the purpose of manipulating melatonin
Melatonin
Melatonin , also known chemically as N-acetyl-5-methoxytryptamine, is a naturally occurring compound found in animals, plants, and microbes...
levels or timing, light boxes providing very specific types of artificial illumination
Lighting
Lighting or illumination is the deliberate application of light to achieve some practical or aesthetic effect. Lighting includes the use of both artificial light sources such as lamps and light fixtures, as well as natural illumination by capturing daylight...
to the retina of the eye are effective.
Light therapy either uses a lightbox which emits up to 10,000 lux
Lux
The lux is the SI unit of illuminance and luminous emittance, measuring luminous flux per unit area. It is used in photometry as a measure of the intensity, as perceived by the human eye, of light that hits or passes through a surface...
of light, much brighter than a customary incandescent lamp, or a lower intensity of specific wavelengths of light from the blue (470 nm) to the green (525 nm) areas of the visible spectrum
Visible spectrum
The visible spectrum is the portion of the electromagnetic spectrum that is visible to the human eye. Electromagnetic radiation in this range of wavelengths is called visible light or simply light. A typical human eye will respond to wavelengths from about 390 to 750 nm. In terms of...
. Newer light therapy devices use LED technology, making them much smaller and more convenient for users. 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, 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.
In treatment, the patient's eyes are to be at a prescribed distance from the light source with the light striking the retina. This does not require looking directly into the light.
Considering three major factors - clinical efficacy, ocular and dermatologic safety, and visual comfort - CET recommends the following criteria for light box selection:
- Any light box you buy 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.
- Fluorescent lamps should have a smooth diffusing screen that filters out ultraviolet (UV) rays. UV rays are harmful to the eyes and skin.
- The lamps should give off white light rather than colored light. "Full spectrum" lamps and blue (or bluish) lamps provide no known therapeutic advantage.
- 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.
Seasonal affective disorder
While full sunlightSunlight
Sunlight, in the broad sense, is the total frequency spectrum of electromagnetic radiation given off by the Sun. On Earth, sunlight is filtered through the Earth's atmosphere, and solar radiation is obvious as daylight when the Sun is above the horizon.When the direct solar radiation is not blocked...
is preferred for seasonal affective disorder
Seasonal affective disorder
Seasonal affective disorder , also known as winter depression, winter blues, summer depression, summer blues, or seasonal depression, is a mood disorder in which people who have normal mental health throughout most of the year experience depressive symptoms in the winter or summer, spring or autumn...
(SAD), light boxes may be effective for the treatment of the condition. Light boxes for seasonal affective disorder are designed to filter out most UV light, which can cause eye and skin damage. The U.S. Food and Drug Administration has not approved the use of light boxes to treat SAD due to unclear results in clinical trial
Clinical trial
Clinical trials are a set of procedures in medical research and drug development that are conducted to allow safety and efficacy data to be collected for health interventions...
s, but light therapy is still seen as the main form of treatment for SAD. Direct sunlight, reflected into the windows of a home or office by a computer-controlled mirror device called a heliostat
Heliostat
A heliostat is a device that includes a mirror, usually a plane mirror, which turns so as to keep reflecting sunlight toward a predetermined target, compensating for the sun's apparent motions in the sky. The target may be a physical object, distant from the heliostat, or a direction in space...
, has also been used as a type of light therapy for the treatment of SAD.
It is possible that response to light therapy for SAD could be season dependent.
Non-seasonal depression
Light therapy has also been suggested in the treatment of non-seasonal depression and other psychiatric disturbances, including major depressive disorder, bipolar disorderBipolar disorder
Bipolar disorder or bipolar affective disorder, historically known as manic–depressive disorder, is a psychiatric diagnosis that describes a category of mood disorders defined by the presence of one or more episodes of abnormally elevated energy levels, cognition, and mood with or without one or...
and postpartum depression
Postpartum depression
Postpartum depression , also called postnatal depression, is a form of clinical depression which can affect women, and less frequently men, typically after childbirth. Studies report prevalence rates among women from 5% to 25%, but methodological differences among the studies make the actual...
. A meta-analysis by the Cochrane Collaboration
Cochrane Collaboration
The Cochrane Collaboration is a group of over 28,000 volunteers in more than 100 countries who review the effects of health care interventions tested in biomedical randomized controlled trials. A few more recent reviews have also studied the results of non-randomized, observational studies...
concluded that "For patients suffering from non-seasonal depression, light therapy offers modest though promising antidepressive efficacy."
Chronic CRSD
In the management of circadian rhythmCircadian rhythm
A circadian rhythm, popularly referred to as body clock, is an endogenously driven , roughly 24-hour cycle in biochemical, physiological, or behavioural processes. Circadian rhythms have been widely observed in plants, animals, fungi and cyanobacteria...
disorders such as delayed sleep phase syndrome
Delayed sleep phase syndrome
Delayed sleep-phase syndrome , also known as delayed sleep-phase disorder or delayed sleep-phase type , is a circadian rhythm sleep disorder, a chronic disorder of the timing of sleep, peak period of alertness, the core body temperature rhythm, hormonal and other daily rhythms, compared to the...
(DSPS), the timing of light exposure is critical. For DSPS, the light must be provided to the retina as soon after spontaneous awakening as possible to achieve the desired effect, as shown by the phase response curve
Phase response curve
A phase response curve illustrates the transient change in the cycle period of an oscillation induced by a perturbation as a function of the phase at which it is received...
for light in humans. Some users have reported success with lights that turn on shortly before awakening (dawn simulation
Dawn simulation
Dawn simulation is a technique originally developed to help treat seasonal affective disorder, but can be used as a soundless alarm clock to wake up the body naturally...
). Morning use may also be effective for non-24-hour sleep-wake syndrome
Non-24-hour sleep-wake syndrome
Non-24-hour sleep-wake syndrome is a chronic circadian rhythm sleep disorder, classified within Chapter VI, Diseases of the Nervous System, in the ICD-10. It can be defined as "a chronic steady pattern comprising one- to two-hour daily delays in sleep onset and wake times in an individual living...
, while evening use is recommended for advanced sleep phase syndrome
Advanced sleep phase syndrome
Advanced sleep phase syndrome , also known as the advanced sleep-phase type of circadian rhythm sleep disorder, is a condition in which patients feel very sleepy and go to bed early in the evening and wake up very early in the morning Advanced sleep phase syndrome (ASPS), also known as the...
.
Situational CRSD
Light therapy has been tested for individuals on shift workShift work sleep disorder
Shift work sleep disorder is a circadian rhythm sleep disorder characterized by insomnia and excessive sleepiness affecting people whose work hours are scheduled during the typical sleep period...
, and for jet lag
Jet lag
Jet lag, medically referred to as desynchronosis, is a physiological condition which results from alterations to the body's circadian rhythms; it is classified as one of the circadian rhythm sleep disorders...
.
Neonatal jaundice
Neonatal jaundice
Neonatal jaundice or Neonatal hyperbilirubinemia is a yellowing of the skin and other tissues of a newborn infant. A bilirubin level of more than 85 umol/l manifests clinical jaundice in neonates whereas in adults a level of 34 umol/l would look icteric...
through the isomerization of the bilirubin
Bilirubin
Bilirubin is the yellow breakdown product of normal heme catabolism. Heme is found in hemoglobin, a principal component of red blood cells. Bilirubin is excreted in bile and urine, and elevated levels may indicate certain diseases...
and consequently transformation into compounds that the newborn can excrete via urine and stools. A common treatment of neonatal jaundice is the Bili light
Bili light
A bili light is a phototherapy tool to treat newborn jaundice which in higher levels causes brain damage , leading to cerebral palsy, auditory neuropathy, gaze abnormalities and dental enamel hypoplasia. The therapy uses a blue light that converts bilirubin so that it can be excreted in the urine...
.
Parkinson's disease
Bright light therapy may ease Parkinson's diseaseParkinson's disease
Parkinson's disease is a degenerative disorder of the central nervous system...
by reducing patients' tremors.
Safety
UltravioletUltraviolet
Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...
light causes progressive damage to human skin. This is mediated by genetic damage, collagen damage, as well as destruction of vitamin A
Vitamin A
Vitamin A is a vitamin that is needed by the retina of the eye in the form of a specific metabolite, the light-absorbing molecule retinal, that is necessary for both low-light and color vision...
and vitamin C
Vitamin C
Vitamin C or L-ascorbic acid or L-ascorbate is an essential nutrient for humans and certain other animal species. In living organisms ascorbate acts as an antioxidant by protecting the body against oxidative stress...
in the skin and free radical generation. Ultraviolet light is also known to be a factor in formation of cataract
Cataract
A cataract is a clouding that develops in the crystalline lens of the eye or in its envelope, varying in degree from slight to complete opacity and obstructing the passage of light...
s. Researchers have questioned whether limiting blue light exposure could reduce the risk of age-related macular degeneration.
Modern phototherapy lamps used in the treatment of seasonal affective disorder and sleep disorder
Sleep disorder
A sleep disorder, or somnipathy, is a medical disorder of the sleep patterns of a person or animal. Some sleep disorders are serious enough to interfere with normal physical, mental and emotional functioning...
s 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.
It is reported that bright light therapy may activate the production of reproductive hormones, such as testosterone
Testosterone
Testosterone is a steroid hormone from the androgen group and is found in mammals, reptiles, birds, and other vertebrates. In mammals, testosterone is primarily secreted in the testes of males and the ovaries of females, although small amounts are also secreted by the adrenal glands...
, luteinizing hormone
Luteinizing hormone
Luteinizing hormone is a hormone produced by the anterior pituitary gland. In females, an acute rise of LH called the LH surge triggers ovulation and development of the corpus luteum. In males, where LH had also been called interstitial cell-stimulating hormone , it stimulates Leydig cell...
, follicle-stimulating hormone
Follicle-stimulating hormone
Follicle-stimulating hormone is a hormone found in humans and other animals. It is synthesized and secreted by gonadotrophs of the anterior pituitary gland. FSH regulates the development, growth, pubertal maturation, and reproductive processes of the body. FSH and Luteinizing hormone act...
, and estradiol
Estradiol
Estradiol is a sex hormone. Estradiol is abbreviated E2 as it has 2 hydroxyl groups in its molecular structure. Estrone has 1 and estriol has 3 . Estradiol is about 10 times as potent as estrone and about 80 times as potent as estriol in its estrogenic effect...
.
There are few absolute contraindications to light therapy, although there are some circumstances in which caution is required. These include when a patient has a condition that might render his or her eyes more vulnerable to phototoxicity, has a tendency toward mania, has a photosensitive skin condition, or is taking a photosensitizing herb (such as St. John's wort) or medication. Patients with porphyria
Porphyria
Porphyrias are a group of inherited or acquired disorders of certain enzymes in the heme bio-synthetic pathway . They are broadly classified as acute porphyrias and cutaneous porphyrias, based on the site of the overproduction and accumulation of the porphyrins...
should avoid most forms of light therapy. Patients on certain drugs like methotrexate
Methotrexate
Methotrexate , abbreviated MTX and formerly known as amethopterin, is an antimetabolite and antifolate drug. It is used in treatment of cancer, autoimmune diseases, ectopic pregnancy, and for the induction of medical abortions. It acts by inhibiting the metabolism of folic acid. Methotrexate...
or chloroquine
Chloroquine
Chloroquine is a 4-aminoquinoline drug used in the treatment or prevention of malaria.-History:Chloroquine , N'--N,N-diethyl-pentane-1,4-diamine, was discovered in 1934 by Hans Andersag and co-workers at the Bayer laboratories who named it "Resochin". It was ignored for a decade because it was...
should use caution with light therapy as there is a chance that these drugs could cause porphyria.
Side effects
Side effects of light therapy for sleep phase disorders include jumpiness or jitteriness, headache, and nausea. Some nondepressive physical complaints (such as poor vision and skin rash or irritation) may improve with light therapy.See also
- Low level laser therapyLow level laser therapyLow-level laser therapy is a medical and veterinary treatment that uses low-level lasers or light-emitting diodes to alter cellular function...
- Deep penetrating light therapy
- Blood irradiation therapy