What is Light Boxes

The brightness and color temperature of light from a light box are quite similar to daylight.

See also: List of ineffective cancer treatments

The production of the hormone melatonin, a sleep regulator, is inhibited by light and permitted by darkness as registered by photosensitive ganglion cells in the retina. To some degree, the reverse is true forserotonin^{[citation needed]}, which has been linked to mood disorders. Hence, for the purpose of manipulating melaton in levels or timing, light boxes providing very specific types of artificial illumination to the retina of the eye are effective.^{[citation needed]}

Light therapy uses either a light box which emits up to 10,000 lux of light at a specified distance, much brighter than a customary lamp, or a lower intensity of specific wavelengths of light from the blue (460 nm) to the green (525 nm) areas of the visible spectrum.^[39] A 1995 study showed that green light therapy at doses of 350 lux produces melatonin suppression and phase shifts equivalent to 10,000 lux white light therapy,^[40][41] but another study published in May 2010 suggests that the blue light often used for SAD treatment should perhaps be replaced by green or white illumination, because of a possible involvement of the cones in melatonin suppression.^[42]

In treatment, the patient's eyes are to be at a prescribed distance from the light source with the light striking the (lower) retina. This does not require looking directly into the light.

Considering three major factors – clinical efficacy, ocular and dermatologic safety, and visual comfort, the Center for Environmental Therapeutics (CET) recommends the following criteria for light box selection:^[43]

·         Light boxes should have been tested successfully in peer-reviewed clinical trials.

·         The box should provide 10,000 LUX of illumination at a comfortable sitting distance. Product specifications are often missing or unverified; illuminance can be controlled using a light meter.

·         Fluorescent lamps should have a smooth diffusing screen that filters out ultraviolet (UV) rays. UV rays are harmful to the eyes and skin.

·         Blue light is known to be superior to red light in managing depressive symptoms which have a seasonal pattern.^[44]

·         The light should be projected downward toward the eyes at an angle to minimize aversive visual glare.

·         Smaller is not better; when using a compact light box, even small head movements will take the eyes out of the therapeutic range of the light.