Many people who wear sunglasses believe that the darker the colour of the lenses, the safer it may be for the eyes.
Here's the truth.
The colour of the lenses does not necessarily correspond to their protective qualities. Dark colours increase the dilation of the pupil, which leads to more harmful UV rays coming into the eye, than without glasses.
For this reason, when buying sunglasses, one should always pay great attention to the so-called filter categories, which indicate the intensity of the tinting.
Better protection thanks to the filter categories
We wear sunglasses to protect our eyes from sunlight and not to have to use our hand as a shield.
The darker the lenses, the higher the protection.
The levels of protection are divided up into so-called filter categories.The EU categories, which are usually indicated in five digits, Roman (I to V) or Arabic (0 to 4), are helpful here:
|Filter category||Weather conditions||Glass shade||Utilisation|
|0||3 – 20%||Offers the least protection. Colourless or very light filter. Typically sport or protective glasses designed to protect against wind, dust or debris, but not against sun.|
|1||20 – 57%||For partly cloudy days. Very lightly coloured lenses, usually yellow or orange, suitable for weaker sun radiation or as wind or dust protection.|
|2||57 – 82%||Suitable for normal summer days. Medium dark filter suitable for medium sun radiation and for casual wear. The tint is slightly lighter than usual. Can be used for spring and autumn walks on sunny days. They also come in handy while driving and frequently moving between shade and sun.|
|3||82 – 92%||Offers intensive protection. Recommended for holidays by the sea, in Southern Europe and for mountain walks. Dark filter suitable for intensive sun radiation on the beach or in the city. This category is typical for most types of sunglasses. It is perfect for summer because it provides a higher degree of protection against sun radiation than the previous category.|
|4||92 – 97%||Particularly strong protection, which is suitable for high mountains and glaciers. Category 4 sunglasses are forbidden in road traffic. These are marked with the symbol of a crossed-out car. Very dark filter for very intensive sun radiation. Sunglasses for mountains or desserts and everywhere where the sunshine is not just extremely strong, but where it also reflects a lot.|
As good as the quality of the lenses is, up to 60% of the UV rays can penetrate from above or through the sides.
Therefore, large lenses and a wide temple can contribute to optimal protection. In addition, wearing a hat or cap can be helpful.
UV 400 meaning
UV 400 is the category which blocks all light rays with wavelengths up to 400 nanometers. This covers all of UVA and UVB rays. Refer to the above table.
UV rays damage the retina
If you get too close to the sun, you will get a sunburn. The ultraviolet rays – the so-called UV rays – increase the risk of skin cancer. Furthermore, frequent sunbathing can accelerate skin aging.
But it's not only the skin that can be damaged, but the eyes can also be impaired too.
If unprotected eyes are exposed to the sun, a long and intensive irradiation can lead to inflammations of the conjunctiva and cornea.
In the worst case, the visual organ may be damaged in the long term and the lens may become cloudy (cataract).
Therefore always wear sunglasses with guaranteed UV protection!
UV-C rays are basically absorbed by the earth's atmosphere, but UV-B and UV-A rays penetrate unhindered to the earth's surface. The designation UV400 with guaranteed UV protection protects against harmful UV-B and UV-A radiation.
Furthermore, the sunglasses reduce visible light, which makes seeing in the
sunshine more pleasant.
In short, the term UV400 means that the glasses absorb UV-A, B and C rays, up to a wavelength of 400 nanometers.
Other quality features of sunglasses
- CE mark: The CE mark has been existing since 1 July 1995 and indicates that there is UV protection up to at least 380 nanometres. It is located on the inside of the temples and indicates that the model complies with current EU standards.
- Spectacle frame: As already mentioned in the article, sunlight can also infiltrate from above and laterally. Therefore, in order to ensure optimum protection, slightly larger lenses and wider temples can be used.
- Polarization filters: The polarized lenses have a special coating that increases visibility through filtering during exposure to intense light rays. These lenses are designed to reduce the glare of surfaces such as water, snow or glass. Sunglasses with polarizing lenses are particularly suitable for car drivers.