Light therapy with daylight lamps

Light not only allows us to see but also influences the level of endogenous messenger substances such as melatonin or serotonin in the blood.

Light acts as a "timekeeper", setting our body clock, synchronising the human body with its environment, and influencing our mood. These responses are largely mediated by light-sensitive cells in the retina of the eye (photosensitive retinal ganglion cells).

Blue light (wavelengths of around 480 nm) is particularly effective. These wavelengths produce the strongest stimulation of the pigment melanopsin. In the light-sensitive ganglion cells, this pigment is involved in the process of synchronising the body with the day/night cycle.

Artificial sources for light therapy

Light therapy using artificial sources is intended to compensate for a lack of natural sunlight. For example, powerful lamps are used to:

• bolster the sleep/wake cycle

• alleviate symptoms of seasonal affective disorder (SAD), also known as "winter depression".

Light therapy generally uses very bright, powerful lamps with a "daylight white" colour temperature (6,500 kelvin) and illumination intensities (illuminances) of over 10,000 lux (lx), depending on the distance between the user and the lamp.

The safety of the equipment – including with regard to photochemical retinal damage ("blue hazard") – is the responsibility of the manufacturer. The information provided by the manufacturer should clearly state that the device emits neither UV nor infrared radiation.

Recommendations for use

In general, those using optical radiation for therapeutic purposes should not do so without consulting a doctor. Although findings certainly exist that describe the positive effects of light therapy on various symptoms, for example in the case of "winter depression", the question of whether this form of therapy is proportionate and appropriate depends on the diagnosis and should be clarified with a doctor on a case-by-case basis.

Caution is advised:

• in the event of diseases involving increased photosensitivity of the skin
• when taking medications that can cause photosensitivity of the skin (e.g. some antibiotics, anti-inflammatory agents or high-dose preparations of St. John’s Wort)
• in the event of eye diseases such as glaucoma, cataracts or retinal diseases (retinopathies).

In those suffering from eye diseases, an ophthalmologist should first clarify whether light therapy using artificial radiation sources is appropriate.

However, even people without eye diseases should avoid spending long periods of time looking into such a bright light source from a short distance.

Labelling as medical devices

Light therapy devices should be labelled as medical devices and used accordingly. Relatively strict requirements therefore apply to their efficacy and safety. In most cases, these are Class II a medical devices according to Directive 93/42/EEC concerning medical devices.

Users should consult the manufacturer’s information and adhere to the operating instructions, especially in relation to the distance, duration and recommended time of application (usually in the morning).