Ultraviolet (UV) Light
UV light is invisible to the human eye and does not affect circadian rhythm. Its most important effects on health come from absorption by your skin, not through your eyes. The health benefits (and warnings) for UV and bright light are quite different.
UV light is essential for our body’s production of vitamin D (see Vitamin D section). Yet the absorption of UV light by the skin is also associated with suntan, sunburn, long-term skin damage and skin cancer. Note that the best time to get your bright light is early in the morning, when the UV component of sunlight is lower.
Long-term exposure of the eyes to UV light can also be associated with an increased risk of cataracts. UV radiation in sunlight is highest during the mid-day hours (10AM - 2PM). All prescription glasses in the US protect against UV light without reducing the brightness of visible light. Most sunglasses also protect against UV light, while reducing visible light to around 25% of what the naked eye would see. The brightness of the sun near mid-day is far above the amount required for maximal health benefit, so SunSprite can still let you know when you’ve had your right dose even if you’re wearing sunglasses.
SunSprite accurately measures the real-time UV intensity and provides a user with an easy guide to stay safe in high UV levels. For instance, when the UV index is 4, you will see “A UV Index reading of 3 to 5 means moderate risk of harm from unprotected sun exposure.” And if UV is 12, you will see: “A UV Index reading of 11 or more means extreme risk of harm from unprotected sun exposure. Take all precautions because unprotected skin and eyes can burn in minutes.”
If you wish to avoid any possibility of UV exposure while getting the full benefits of bright light, you can either receive your bright light through a window or purchase a therapeutic light box. SunSprite lets you move around when you use a light box and still be sure that you have received the right the “dose” of light.
Tanning beds are just the opposite – UV exposure without the visible light. There is no good reason to visit them.