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Melatonin suppression by illumination of upper and lower visual fields
T A Lasko1, D F Kripke, J A Elliot
1Department of Psychiatry, University of California, San Diego, La Jolla 92093-0667, USA.
Journal of Biological Rhythms
|April 9, 1999
Summary
Bright light therapy, especially in the upper visual field, effectively suppresses melatonin. This finding suggests optimizing light treatment for circadian rhythm and mood disorders.
Area of Science:
- Chronobiology
- Neuroendocrinology
- Ophthalmology
Background:
- Bright light therapy is a common treatment for circadian rhythm disorders and depression.
- The effectiveness of light therapy may depend on light delivery parameters, including visual field.
- Melatonin suppression is a key physiological response to light exposure.
Purpose of the Study:
- To investigate the impact of light exposure in different visual fields on melatonin suppression.
- To determine optimal light geometry for bright light treatment.
Main Methods:
- 12 healthy subjects participated in a laboratory study.
- Subjects received 500 lux in the upper visual field, 500 lux in the lower visual field, or 5 lux (control) during evening hours.
- Melatonin levels were measured to assess light's physiological impact.
Main Results:
- 500 lux in the upper visual field significantly suppressed melatonin compared to lower visual field or dim light.
- 500 lux in the lower visual field showed intermediate, borderline significant melatonin suppression.
- Dim light (5 lux) showed minimal melatonin suppression.
Conclusions:
- Light exposure in the upper visual field is more effective at suppressing melatonin.
- Optimizing light treatment for circadian phase disorders and depression may involve directing light to the upper visual field.