- 1 Info
- 2 Medical Uses
- 3 Side effects, Risks etc
- 4 Internal Links
Also called phototherapy, classically referred to as heliotherapy, consists of exposure to daylight or to specific light wavelengths, and makes use of polychromatic polarised light, lasers, light-emitting diodes, fluorescent lamps, dichroic lamps or very bright, full-spectrum light.
These light sources are used by the patient for a pre-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.
Light therapy which strikes the retina of the eyes is used to treat circadian rhythm disorders such as delayed 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.
Two forms of phototherapy exist for skin conditions: non-targeted phototherapy (from sunlight or a light box), and targeted phototherapy, in which light is administered to a specific,localised area of the skin.
Current targeted phototherapy is administered via excimer laser, elemental gas lamp, or via LED light.
Current FDA cleared devices on the market include XTRAC excimer laser, BClear, Theralight, and Psoria-Light LED phototherapy. Targeted phototherapy is administered in a doctor's office and is only administered to the affected skin, not the entire body, thus sparing healthy skin from UV rays which may lead to other health issues including skin cancer. While different wavelengths work for different conditions, treatment is most often done with narrow band UVB (NB-UVB) as this is the safest wavelength. Non-targeted phototherapy can be delivered at doctor's office or at home via prescription (USA) using a booth, multidirectional unit, or wand. The unaffected skin is simply covered. Several devices are FDA-approved for home including the Panosol 3D and Richmond Light and Solarc Handheld.
In this case, UVB phototherapy has been shown to be effective. 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 usually use NB-UVB (311 nm wavelength) though 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 sensitivity). The time is controlled with a timer that turns off the lamps after the treatment time ends.
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."
Evidence for light therapy and lasers in acne vulgaris as of 2012 is not sufficient to recommend them. 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.
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 treatment 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.
Other skin conditions
Phototherapy can be effective in the treatment of eczema, atopic dermatitis, polymorphous light eruption and lichen planus. Narrowband UVB lamps, 311–313 nanometer is the most common treatment.
Some case studies have found low-level laser light to be possibly helpful as an adjunctive 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.
Seasonal affective disorder
Full sunlight or exposure to bright light from a light box is used to treat seasonal affective disorder (SAD).
Light boxes for SAD are designed to filter out most UV light, which can cause eye and skin damage. Mayo Clinic states that light therapy has proven effectiveness for treating seasonal affective disorder and light therapy is seen as its main form of treatment. Controlled-trial comparisons with antidepressants show equal effectiveness, with less expense and more rapid onset of therapeutic benefit, though a minority of patients may not respond to it. 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.
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. Studies show that light therapy helps reduce the debilitating and depressive behaviors of SAD, such as excessive sleepiness and fatigue, which 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.
It is possible that response to light therapy for SAD could be season dependent. Morning therapy has provided the best results because light in the early morning aids in regulating the circadian rhythm.
Light therapy has also been suggested in the treatment of non-seasonal depression and other psychiatric disturbances, including major depressive disorder, bipolar disorder 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." A more recent meta-analysis from Journal of Affective Disorders confirms this and is even more hopeful: "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."
Circadian rhythm sleep disorders
In the management of circadian rhythm disorders such as delayed sleep phase disorder (DSPD), the timing of light exposure is critical. For DSPD, 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 disorder, while evening use is recommended for advanced sleep phase disorder.
Light therapy has been tested for individuals on shift work, and for jet lag.
Sleep disorder in Parkinson's disease Light therapy has been trialed in treating sleep disorders experienced by patients with Parkinson's disease.
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.
Side effects, Risks etc
Ultraviolet light causes progressive damage to human skin.
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 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.
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 such as methotrexate or chloroquine should use caution with light therapy as there is a chance that these drugs could cause porphyria.
Side effects of light therapy for sleep phase disorders include jumpiness or jitteriness, headache, eye irritation and nausea. Some nondepressive physical complaints (such as poor vision and skin rash or irritation) may improve with light therapy.