For SAD, phototherapy initially consisted of exposure at a 3-foot distance to a light source of 2500 lux for two hours daily. Light boxes have been re-designed to deliver an intensity of 10,000 lux at a distance of 12 inches on a downward angle. Since these are not portable or mobile, head-mounted devices were developed. Light visors are an adaptation that provide a greater mobility and adjustable light intensity. The dosages vary from these full-spectrum light sources.
Some patients require morning and night exposure.
The light visor appears to function quite differently from the light box. Studies seem to agree that bright light greater than 2500 lux is more effective than dim light of less than 500 lux. The proposed mechanism, as discussed above, is that of alteration of the circadian rhythm through adjustment of melatonin secretion. As innocuous as phototherapy sounds, it has been associated with some side effects. Most side effects have been limited and mild and remit with the discontinuation of the light therapy.