What You Should Know about UV Rays and Healthy Eyes

_{Article first published: May 2022}

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.
  

The skin can be protected from the dangers of UV radiation very effectively by using sunscreen and clothing. There is also a simple solution for the eyes: protect them by wearing good sunglasses that absorb UV radiation up to 400 nm. The color is only relevant to protection from glare and has no bearing on the UV protection. This is determined by the lens material. Therefore, care must always be taken to ensure that the actual protection extends to 400 nm. This can be relied on when it comes to sunglasses from the eye care professional. And nowadays, intelligent sunglasses such as ZEISS AdaptiveSun have the capacity to adapt their tint levels to the current light conditions. If you want to make sure that as little UV radiation as possible reaches your eyes and the area around them, choose sunglasses with wide temples and large lenses.

On the other hand, dark sunglasses whose material does not provide full UV protection are dangerous. The tint makes the pupils expand. Low-quality material means that more harmful radiation can enter the eye. This is especially exacerbated when the glasses do not provide protection at the sides due to insufficiently curved sunglasses and when UV radiation from the side, or reflecting into the eye from the inside of the glass, increases the exposure even more.

Because UV radiation can also be dangerous when it is cloudy or in the shade, people who need a visual aid anyway have a decisive advantage. Since 2018, clear ZEISS lenses also offer UV protection at sunglass level up to 400 nm – always and everywhere, even if sunglasses are not used at that moment. Likewise, phototropic lenses are a real everyday convenience. Like all ZEISS lenses, they provide full protection against UV radiation at all times but offer the advantage of darkening when necessary. Thus, three functions are combined: visual aid, UV protection and glare protection. In addition, ZEISS PhotoFusion X self-tinting lenses absorb some of the potentially harmful and irritating blue light, which in turn supports vision, especially during intensive screen work.
In general, the following rule applies: If the UV index is high, the midday sun should generally be avoided. Personal UV exposure should then be kept low, whether through clothing, sunglasses, or by a conscious decision to stay indoors.

• Featured Story: Summer, Sun and Eye Protection
  
• Background article: Full UV Protection - Also With Clear Lenses
  
• Tips For The Right Prescription Sunglass Lenses