Light therapy design

Melatonin suppression by illumination of upper and lower visual fields
J Biol Rhythms. 1999 Apr;14(2):122-5
As a guide to optimising the geometry of bright light treatment, 12 healthy subjects were studied three times in the laboratory. The results suggest that bright light treatment of depression or circadian phase disorders might be most effective when applied in the upper visual field.

Mechanisms in the eye that mediate the biological and therapeutic effects of light in humans
Proceedings of the Werner-Gren Centre International Symposium on Light & Biological Rhythms in Man, Stockholm. 1992
It appears that ... the more retinal area exposed to light, the stronger the resulting biological response.

Size matters! Light coming from a large area - in other words a larger window on the light - is more effective. Pharos has the largest window size.

30-minute light therapy at 10,000lux
SLTBR Abstracts. 1989 June
The short duration/high intensity method (30minute/10,000lux) matches or exceeds the level of efficacy found with conventional (2hr/2500lux) treatment. Evaluations indicated a strong preference among patients for 10,000 lux. Opthalmological examination showed no clinically significant retinal abnormalities or changes in visual performance.

Lux is a measure of brightness. Dr N Rosenthal (who first described SAD and Light Treatment) said in May 1992, "I am quite convinced 10,000lux is superior to 2,500lux". The Pharos range all deliver 10,000lux at 50cm.

Back to Resource Centre»