A reader asks:
Exactly how far from a 10,000 lux light box should I sit, and where should I place it? It is 2-feet wide and 1-foot high. Do I place it above eye level? Stare directly at it?
Light Boxes in General
The lux level at your eyes depends on your distance from the light box screen. There is no such thing as a “10,000 lux light box;” rather, a light box may be capable of providing 10,000 lux if it has appropriate dimensions, number of lamps, lamp power, filtering, etc. Some manufacturers give deceptively high lux measurements, made with an instrument that focuses narrowly into the lamps, whereas the eyes take in the whole illuminated environment. That problem is especially true for recent, relatively tiny lighting devices, which we do not expect are therapeutically active.
Your Light Box
A light box of 2 x 1 ft may be adequate; it depends on the bulbs inside, the screen filter and the distance. You have to trust the manufacturer for specifying the required distance and unfortunately the information given is not always accurate. We always recommend that the box be placed at or above the line of sight in order to project light downward toward the eyes. Boxes that rest on a tilting stand are best. Such an arrangement greatly reduces aversive glare of the high intensity light. One should never stare directly into a light box, but instead orient forward and concentrate on reading, writing, breakfast, etc., in the illuminated field. For more info, see the articles on our page on light boxes, including Light Therapy for Beginners: Six Steps