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Light therapy
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Light therapy or phototherapy consists of exposure to daylight or to specific wavelengths of light using lasers, LEDs, fluorescent lamps, dichroic lamps or very bright, full-spectrum light, for a prescribed amount of time and, in some cases, at a specific time of day. It has proven effective in treating Acne vulgaris, seasonal affective disorder, neonatal jaundice, and is part of the standard treatment regimen for delayed sleep phase syndrome. It has recently been shown effective in non-seasonal depression.
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Encyclopedia
Light therapy or phototherapy consists of exposure to daylight or to specific wavelengths of light using lasers, LEDs, fluorescent lamps, dichroic lamps or very bright, full-spectrum light, for a prescribed amount of time and, in some cases, at a specific time of day. It has proven effective in treating Acne vulgaris, seasonal affective disorder, neonatal jaundice, and is part of the standard treatment regimen for delayed sleep phase syndrome. It has recently been shown effective in non-seasonal depression. Proponents claim demonstrable benefits for skin conditions such as psoriasis.
Skin related
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 treatment due to the likelihood of skin damage in the long term. However, artificial UV didn't work as well as sunlight.
It was found that some of the visible violet light, present in sunlight, in the range 405-420 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
. This part of the spectrum is just outside the ultraviolet and produces little if any tanning or sunburn.
Application of the light for 3 consecutive days has been shown to reduce the bacteria in the pores by 99.9%. 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 fluorescent lamps, bright LEDs or dichroic filament bulbs.
Treatment is often accompanied by application of red light which has been shown to activate ATP in human skin cells (essentially a photobiomodulation effect), and seems to improve response rates.
Overall improvements of on average 76% for 80% of patients occurs over 3 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.
Home use light boxes usually work well, are effective for people with long-term acne, are likely to be cheaper than light treatments at a dermatologist's office, and can be repeated over several years for negligible cost. The light at a dermatology clinic may be of a higher intensity, however.
Psoriasis and eczema
A feature of psoriasis is localised inflammation mediated by the immune system. UV radiation is known to suppress the immune system and reduce inflammatory responses. Light therapy for skin conditions like psoriasis or eczema use UVA (315-400nm waveband) or UVB (280-315nm waveband) light waves. UVA, combined with a drug taken orally, is known as PUVA treatment. Narrow Band UVB is the 310nm wave length and is given as a light therapy treatment rather than full spectrum UVB.
Tanning
Tanning is caused by the effects of two different spectrums of ultraviolet radiation: UVA and UVB. Excessive ultraviolet exposure in doses used in tanning salons may be associated with carcinogenesis.
Wound healing and neuropathy
Monochromatic infrared light emitted at a wavelength of 890 nm has been shown effective, through limited clinical studies, to help restore sensation and reduce pain in patients with neuropathy and to improve circulation of non-healing ulcers, thus increasing their healing rate. It is thought that the infrared light helps to release nitric oxide into the bloodstream, which aids in increasing local circulation and improving blood flow. People with diabetes have poor circulation due to their naturally low levels of nitric oxide and sedentary habits.
Photodynamic therapy
Visible blue light is used with aminolevulinic acid for the treatment of Actinic keratosis. This is not a U.S. FDA-approved treatment for acne vulgaris.
Mood and sleep related
Light boxes
For the purpose of manipulating melatonin and serotonin levels or timing, light boxes providing intense artificial illumination are effective. These lamps, at a prescribed distance, provide up to 10,000 lux directed angularly at the user's eyes, without harmful ultraviolet radiation.
The production of the hormone melatonin, a sleep regulator, is inhibited by light and permitted by darkness. To some degree, the reverse is true for serotonin, which has been linked to mood disorders.
Recent research indicates that using a lower intensity of certain wavelengths of light, i.e., the "blue" wavelengths, may be at least as efficacious as using the customary high-intensity white light, at least until one approaches old age when blue light is no longer more effective than red or green, due to natural yellowing which blocks blue light. The most effective wavelengths of blue light are by most sources given as ranging between 460 nm and 485 nm, a deep blue, with some sources specifying peak photopigment sensitivity at 479 nm (in mice), others at 484nm.
Seasonal affective disorder
While full sunlight is preferred for seasonal affective disorder (SAD), light boxes are also effective. When used for SAD and Bipolar Disorder with SAD features, the effect is most likely created by modification of the melatonin response.
It is possible that response to light therapy for SAD could be season dependent. Also, in one study, untreated patients compared to controls had higher daytime levels of melatonin in winter, but no difference in daytime melatonin during summer or after treatment in winter. In a comparative study, a presumed supersensitivity of melatonin receptors in SAD and bipolar SAD patients was observed where melatonin production was suppressed by dim light during the night, a suppression which was not observed in non-seasonal depressives or controls.
Serotonin may also play a role. A study in 1992 found that serum serotonin levels increase in response to bright light therapy.
Non-seasonal depression
Only recently have clinical studies been conducted which specifically excluded all patients with any degree of seasonality. Before these studies, it was suspected that any depressed patients who benefitted from light treatment were really only having the SAD component of their depression treated. However, light therapy is now an established treatment for depression, regardless of seasonality. One advantage it may have compared with drugs is that results may appear more quickly; antidepressant drugs typically take several weeks to reach full effectiveness. A combination of light and medicine has been proven to be more effective and faster than either alone.
Circadian rhythm sleep disorders
Chronic
In the management of circadian rhythm disorders such as delayed sleep phase syndrome (DSPS), the timing of light exposure is critical. For DSPS, the light must be provided 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 (ASPS).
Situational
Light therapy is sometimes prescribed for shift work sleep disorder, which affects people who work nights or rotating shifts, and for jet lag, which affects people who travel across several time zones.
NASA has used timed doses of bright light to prepare astronauts for late night launches since 1991.
Neonatal jaundice
Light energy creates isomerization of the bilirubin and consequently transformation into compounds that the newborn can excrete via urine and stools.
Parkinson's disease
A recent study has shown that bright light therapy can ease Parkinson's disease by reducing patients' tremors.
Heliotherapy
Within the tanning and spa industry the term "heliotherapy" has become popular to describe medical therapy by exposure to light, usually in the UVA/UVB range. This could include direct sunlight but more often refers to the use of tanning beds, lamps and booths which make use of both ultraviolet and infrared. The treatment of psoriasis, eczema, vitamin D deficiency and seasonal affective disorder are included. As with any exposure to UV, there are some risks associated, but these are usually outweighed by the benefits provided by the treatments. Often, UV treatments are given at a doctor's office, but it is becoming more common for a doctor to prescribe regular visits in a tanning bed for persons who have moderate problems, as this is lower in UV than medical devices, and is more convenient and less expensive for the patient. In very rare and extreme cases, the purchase of home tanning beds is prescribed by doctors and covered by insurance.
There is also evidence that exposure to some frequencies of light (UV in particular) causes the body to release small amounts of endorphins, which would explain the benefit for some disorders such as SAD, as endorphins are often called "the body's own morphine", as well as the concerns for potential tanning addiction, not to be confused with what is commonly called tanorexia, a psychological syndrome wherein patients see themselves as pale, even if they have a substantial tan.
Disadvantages
Safety of phototherapy
Ultraviolet 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.
Visible blue light has been suggested to cause DNA breaks, but carcinogenesis has not been demonstrated, and enzymes within the cells are believed to repair the breaks reasonably well. However, cancer has been induced in cells with deliberately damaged repair mechanisms. Also, researchers have questioned whether limiting blue light exposure could reduce the risk of age-related macular degeneration (ARMD).
Modern phototherapy lamps used in the treatment of seasonal affective disorder and delayed sleep-phase syndrome 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 (BLT) may activate the production of reproductive hormones, such as testosterone, luteinizing hormone (LH), follicle-stimulating hormone (FSH), and estradiol (E2).
There are thus few absolute contraindications to light therapy, although there are some circumstances in which caution is required. These include when a patient 1) has a condition that might render his or her eyes more vulnerable to phototoxicity, 2) has a tendency toward mania, 3) has a photosensitive skin condition, or 4) 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 methotrxate or chloroquine 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, feeling "wired," headache, and nausea. Some nondepressive physical complaints (such as poor vision and skin rash or irritation) may improve with light therapy (M. Terman and Terman 1999).
See also
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