How Light Therapy Works
In light therapy, patients
suffering from SAD or seasonal affective disorder are exposed to intense
levels of light under prescribed and controlled conditions.
The light therapy system comprises
a set of fluorescent or LED bulbs that are installed in a box, which has a
diffusing screen. This whole device is set up at a level at which the
patient can sit comfortably for a treatment session.
During a light therapy session
the lights are put on in the light box and the individual sits close
to the source of light with their eyes open. The important aspect of
light therapy is that the light only works to cure symptoms of SAD if
it enters the body through the eyes. However patients undergoing treatment
are advised not to look directly into the source of light for fear of
causing irreparable damage to the retina. Instead patients are free
to engage in any other activity including reading, writing or eating,
while at the same time orienting their head and body towards the source
of the lights.
Patients could be required
to undergo treatment one or twice a day and a treatment session could
last from 15 minutes to three hours. Duration and frequency of light
therapy sessions differ for different individuals depending on the severity
of the patient’s conditions as well as the equipment that is being
used. SAD patients would need shorter therapy sessions at a system that
delivered 10,000 lux illumination as compared to those undergoing treatment
at a system that delivers 2,500 lux illumination.
Different SAD patients also
responded differently to treatment of the same intensity and at the
same frequency. Clinical trials showed that some patients showed a significant
improvement in depressive symptoms with treatment sessions that lasted
30 minutes per day. For other patients however, fifteen minutes was
sufficient to bring about the similar amount of improvement whereas
a few others required light therapy sessions that lasted at least one
hour.
Another factor that affected
the success of the treatment was the time of the day of light therapy.
Most people respond better when they undertake treatment first thing
after they wake up, whereas others responded better to evening light.
Early light boxes utilized
“full-spectrum” bulbs that produced bright light that was comprised
of the same color composition as outdoor light. Advancements in technology
have now given rise to light boxes that use triphosphor, bi-axial and
cool-white lamps. The characteristic feature of these systems is that
the level of light that is produced is similar in intensity and quality
as the outdoors light just before sunset or soon after sunrise.
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