Like light and infrared radiation, UV radiation is emitted by the sun. The UV spectrum is split into UVA (315-400 nanometers, nm), UVB (280-350 nm) and UVC (100-280 nm). UVC is absorbed by the ozone layer and therefore doesn't reach the Earth. However, UVA and some UVB radiation does reach us. UVA can penetrate deeply into the tissue, including the eyes and skin.
This means that wherever there is sunlight, there is UV radiation. Not only in direct sunlight, but also in the shade or when it is cloudy. Because UV radiation is reflected and scattered, UV exposure levels can be high even in the shade. Particularly high values are reached when scattering and reflection interact, for example when skiing on white snowfields. Other materials reflect UV less. For instance, green spaces and forests always counteract high UV exposure.
The degree to which UV radiation affects us depends on personal UV exposure and the UV index. The UV index sums up the strength of UV radiation (the UV spectrum is weighted differently, depending on the sunburn effectiveness), which depends on geography and altitude, as well as the composition of the ozone layer, the weather and the time of day, among other factors. The WHO describes the UV index as follows: "The values of the index range from zero upward - the higher the UVI, the greater the potential for damage to the skin and eye, and the less time it takes for harm to occur."1 Personal UV exposure is related to the UV index, but is additionally dependent on protective factors such as clothing, sunscreen, and behavior. In other words, things that we can influence individually.
First of all, sunlight is important for our well-being and for the body's own vitamin D production. Vitamin D is manufactured in the upper skin layers with the help of UVB. However, it is the dose that makes the poison. And everyone knows that too much UV radiation also poses dangers to the skin – and, unfortunately, to the eyes. It's important to understand that UV radiation can result in short-term negative effects such as photokeratitis, a type of sunburn of the cornea. But, beyond this, it can also cause long-term problems for the eyes.
- UV radiation can promote the formation of eyelid basal cell carcinoma (white skin cancer).2
- "Wrinkles" – the sensitive skin around the eye is particularly susceptible to UV-induced skin aging.
- High UV exposure can also cause "corneal sunburn" (also called photokeratitis), which results in temporary pain, tears, twitching, light sensitivity, and contracted pupils.
- UV radiation also affects the lens of the eye. UV radiation can accelerate the process of clouding (cataracts) because the risk increases with frequent UV exposure. If a cataract remains untreated, there is a risk of blindness. However, already a developing cataract can reduce contrast or color perception even before it is diagnosed.
- Some scientists consider UV radiation as one of the contributing factors to age-related macular degeneration.
Spend time outside on a regular basis! Our bodies need sunlight to produce vitamin D.
Keep the UV index in mind! This can help you stay informed on how to best protect yourself from UV radiation on a particular day.
Reduce your own level of UV exposure, i.e. how much UV radiation you're exposed to! But don't forget: even in the shade or on a cloudy day, UV rays still reach us.
Wear suitable clothing, a pair of sunglasses or clear eyeglass lenses with UV protection, and put on a hat in strong sunlight!
Don't forget sunscreen!