This therapy helps a person maintain a consistent circadian rhythm by sending a properly timed signal of light through the retina of the eye to the brain's suprachaismatic nucleus, or body clock in the hypothalamus Circadian rhythm disturbances respond very well to light therapy, especially bright light (>600 Lux). The timing of light therapy also is important as it affects the degree and direction of the rhythm shift. The modes of therapy for different disorders are:

Light therapy applied in the early evening and nighttime hours will delay the cycle for Advanced Circadian Rhythm Disorder (ACR)

In the early morning light therapy will stimulate morning alertness and an earlier bedtime for Delayed Circadian Rhythm Disorder (DCR).

Bimodal Circadian Rhythm Disorder (BCR) may cause a person to be awake during the night, so it is important to avoid light during the night. Use bright light in the mid morning, afternoon, late afternoon and evening while avoiding bright morning light before 9:00 am.

For sighted people, bright morning light should regulate Non 24-hour Sleep/Wake Cycle symptoms or a free running circadian rhythm

Light therapy should always be used within the proper limits for intensity and time. Minor side effects may include the following:

Eye irritation and dryness

Headache

Nausea

Dryness of skin