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Phototherapy, or light therapy, is the administration of doses of bright light in order to normalize the body's internal clock and/or relieve depression.


Phototherapy is prescribed primarily to treat seasonal affective disorder (SAD), a mood disorder characterized by depression in the winter months, and is occasionally employed to treat insomnia and jet lag. The exact mechanisms by which the treatment works are not known, but the bright light employed in phototherapy may act to readjust the body's circadian (daily) rhythms, or internal clock. Other popular theories are that light triggers the production of serotonin, a neurotransmitter believed to be related to depressive disorders, or that it influences the body's production of melatonin, a hormone derived from serotonin that may be related to circadian rhythms.


Patients with eye problems should see an ophthalmologist regularly, both before and during phototherapy. Because some ultraviolet rays are emitted by the light boxes used in phototherapy, patients taking photosensitizing medications (medications making the skin more sensitive to light) and those who have sun-sensitive skin should consult with their physician before beginning treatment. Patients with medical conditions that make them sensitive to ultraviolet rays should also be seen by a physician before starting phototherapy. Patients who have a history of mood swings or mania should be monitored closely, since phototherapy may cause excessive mood elevation in some individuals.


Phototherapy is generally administered at home. The most commonly used phototherapy equipment is a portable lighting device known as a light box. The box may be mounted upright to a wall, or slanted downwards towards a table. The patient sits in front of the box for a prescribed period of time (anywhere from 15 minutes to several hours). Some patients with SAD undergo phototherapy sessions two or three times a day, others only once. The time of day and number of times treatment is administered depend on the physical needs and lifestyle of the individual patient. If phototherapy has been prescribed for the treatment of SAD, it typically begins in the fall months as the days begin to shorten, and continues throughout the winter and possibly the early spring.
The light from a slanted light box is designed to focus on the table it sits upon, so patients may look down to read or do other sedentary activities during therapy. Patients using an upright light box must face the light source (although they need not look directly into the light). The light sources in these light boxes typically range from 2,500-10,000 lux. (In contrast, average indoor lighting is 300-500 lux; a sunny summer day is about 100,000 lux).
Phototherapy prescribed for the treatment of SAD may be covered by insurance. Individuals requiring phototherapy should check with their insurance company to see if the cost of renting or purchasing a light box is covered.


Patients beginning light therapy for SAD may need to adjust the length, frequency, and timing of their phototherapy sessions to achieve the maximum benefit. These patients should keep their doctor informed of their progress and the status of their depressive symptoms. Occasionally, antidepressants and/or psychotherapy may be recommended as an adjunct to phototherapy.


An abnormally elevated or expansive mood (hypomania) may occur, but it is usually temporary. Some patients undergoing phototherapy treatment report side effects of eyestrain, headaches, insomnia, fatigue, sunburn, and dry eyes or nose. Most of these effects can be managed by adjusting the timing and duration of the phototherapy sessions. A strong sun block and eye and nose drops can alleviate the other problems. Long-term studies have shown no negative effects to the eye function of individuals undergoing phototherapy treatments.

Normal results

Patients with SAD typically report an alleviation of depressive symptoms within two to 14 days after beginning phototherapy.



National Institute of Mental Health. Mental Health Public Inquiries, 5600 Fishers Lane, Room 15C-05, Rockville, MD 20857. (888) 826-9438.
Society for Light Treatment and Biological Rhythms. P.O. Box 591687, 174 Cook St., San Francisco, CA 94159-1687.

Key terms

Circadian rhythm — The rhythmic repetition of certain phenomena in living organisms at about the same time each day.
Lux — A standard unit of measure for illumination.
Neurotransmitter — A chemical in the brain that transmits messages between neurons, or nerve cells.
Photosensitivity — An abnormally heightened reaction to light.
Seasonal affective disorder (SAD) — Amooddisorder characterized by depression during the winter months. An estimated 11 million Americans experience SAD.


treatment of disease by exposure to light; one example is the treatment of nonhemolytic hyperbilirubinemia in the newborn. Phototherapy reduces bilirubin levels in the blood by decomposing unconjugated bilirubin into colorless compounds excreted in the bile. Photodecomposition is a normal alternative route for the excretion of bilirubin; the use of artificial light hastens this process. Either sunlight or an ultraviolet lamp is effective; the distance of the ultraviolet lamp from the subject is important.
Patient Care. Although phototherapy is inexpensive and relatively easy to use, it is not without danger to the newborn. Damage to the retina by prolonged exposure to the bright light, as well as drying of the cornea, can lead to permanent impairment of vision. To protect the newborn the eyes must be covered for the entire time the child is under the light. The use of eyedrops every two hours can help prevent excessive drying. Insensible water loss due to rapid evaporation of water from the skin can cause a fluid volume deficit. Hence the newborn must be assessed periodically for signs of fluid volume deficit; the monitoring of fluid intake and output and the status of skin turgor are especially important. Because increased body heat is also possible, careful attention must be paid to thermoregulation in order to avoid hyperthermia.
neonate phototherapy in the nursing interventions classification, a nursing intervention defined as the use of light therapy to reduce bilirubin levels in newborn infants; see phototherapy.
ultraviolet phototherapy the use of ultraviolet radiation (which may be type A, B, or C, or a combination of types) in the treatment of skin diseases. The radiation is generated by an artificial source such as an arc lamp and may be used in combination with photosensitizing drugs; see also photochemotherapy.


Treatment of disease by means of light rays.
Synonym(s): light treatment


n. pl. photothera·pies
The treatment of a disorder, especially of the skin, by exposure to light, including ultraviolet and infrared radiation.

pho′to·ther′a·peu′tic (-pyo͞o′tĭk) adj.


Mainstream medicine
Bright light therapy, see there.

Experimental oncology
A therapy in which various conditions (colorectal cancer, cutaneous T-cell lymphoma, head and neck cancer, Kaposi sarcoma, psoriasis, skin cancer) are treated by light after previous administration of the agent haemoporphyrin.


Neonatology Bright light therapy, see there Oncology Photochemotherapy, photodynamic therapy A therapy in which various conditions–eg, colorectal CA, cutaneous T-cell lymphoma, head & neck CA, KS, psoriasis, skin CA are treated by light after previous administration of agents–eg, hemoporphyrin that become active after exposure to light.


Treatment of disease by means of light rays.
Synonym(s): light treatment.


Treatment with light, especially in conjunction with a sensitizing drug such as the psoralen methoxalen. This is known as PUVA (psoralen ultraviolet-A) therapy and is useful in the management of PSORIASIS. Ultraviolet therapy is sometimes used in the treatment of ACNE, and blue light is used to treat babies with JAUNDICE due to liver inadequacy. This alters BILIRUBIN in the skin to a form that can be excreted in the urine.
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Kasparova and Kasparov [22] combined PRK with phototherapeutic keratotectomy (PTK) to treat primary keratoconus.
Following OT's CET article on phototherapeutic keratectomy (PTK) in the February edition, the authors present three cases from practice to demonstrate the practical applications of the technique.
CL intolerance due to corneal nodule formation in KC might be successfully treated performing anterior stromal puncture of the cornea [83] or phototherapeutic keratectomy [84].
* Phototherapeutic keratectomy: cases in practice by Victoria Rowe and Prashant Shah
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Some corneal surgery and corneal refractive surgery with excimer laser ablation were done directly on corneal epithelium, such as transepithelial photorefractive keratectomy (TransPRK) [5] and phototherapeutic keratectomy (PTK).