Sunglasses to protect yourself from UV rays

Sunglasses are one of the main fashion accessories to characterize your “look”, but too often their function in protecting the eyes from ultraviolet (UV) rays is underestimated.

It should not be forgotten that sunlight contains radiation that, over time, can damage the retina and cause serious damage such as cataracts or inflammation of the cornea.

For this reason, when purchasing a new pair of sunglasses, in addition to aesthetic aspects related to personal taste, it is a good idea to check that the level of protection of the lenses is adequate to ensure the well-being of our eyes.

What are UV rays?

Ultraviolet (UV) radiation is a component of sunlight characterized by very short wavelengths, between 100 and 400 nanometers (nm), and is usually divided into three main categories: UVA (315-400 nm) UVB (280-315 nm) UVC (100-280 nm)

UVA rays account for approximately 95% of the ultraviolet radiation that reaches our eyes and can cause damage to the retina, cornea, and, of course, the skin. UVB rays are less present but even more dangerous because their effects are generally more profound and long-lasting. Finally, UVC rays are thought to be the most dangerous for damaging human eyes and skin, but fortunately they are blocked by the ozone layer in our atmosphere, so they do not require specific protection (except in special cases, such as protection from the light emitted by an electric soldering iron).

Which lenses protect against UV rays?

There are various levels of protection against ultraviolet radiation, but it is essential to point out that counterfeit or non-CE certified glasses are most likely equipped with lenses without any level of solar filter and can therefore be very dangerous for the wearer.

Original glasses with CE certification , in addition to other quality requirements, guarantee adequate protection up to 380 nm, therefore including the UVA and UVB range.

Caution: To be authentic, the CE marking must be permanently and legibly engraved on the surface of the glasses; if it is only applied with an adhesive, and therefore removable, they are certainly fake.

To make the presence of an ultraviolet filter more explicit, lenses may bear the indication “ UV400 ” (to mean that they block UV radiation up to 400 nm) or alternatively “ 100% UV protection ”; the two definitions are equivalent.

Lens classification and UV protection

Sunglasses lenses are divided into five categories based on their ability to reduce the amount of light reaching the eyes. Therefore, from the lightest to the darkest lenses, we find:

• Category 0: 80-100% of light passes through the lenses
• Category 1: 43-79% of light passes through the lenses
• Category 2: 18-42% of light passes through the lenses
• Category 3: 8-17% of light passes through the lenses
• Category 4: 3-7% of light passes through the lenses

In this case, the parameter taken into consideration for the classification is the entire light spectrum and therefore it is important to underline that there is no direct relationship with the degree of protection against UV rays .

It's therefore essential to understand that darker lenses don't necessarily offer greater protection . In fact, wearing dark lenses without UV protection causes the pupils to dilate, exposing the inside of the eye and the retina to more harmful radiation. At least, if we don't wear sunglasses, the pupil constricts and allows less harmful rays to enter.

Lenses with UV400 protection typically belong to Category 3 (or 4), providing optimal protection even against visible light in very sunny conditions. However, as mentioned, UV400 protection can also be found on lighter lenses.

UV protection is typically present inside the lens or applied to its external surface: for example, some materials such as polycarbonate already contain a filter inside that ensures 100% protection from UV rays, while for other materials such as CR39 plastic it is normally necessary to add a filtering layer to the surface.

Do polarized lenses protect from UV rays?

The two types of protection should not be confused. Polarized lenses are designed to prevent glare from light reflecting off flat surfaces like snow, water, sand, or asphalt. The resulting abnormal and annoying reflection is filtered by the lens, improving visibility and the quality of colors perceived in these types of situations.

The two protections are therefore not equivalent, but can be complementary to achieve greater visual comfort.

Conclusions

Ultimately, when choosing sunglasses it is essential not to overlook an essential element such as protecting your eyesight .

Although they may appear pleasant, counterfeit glasses or glasses of dubious origin or quality can, in the long run, cause serious damage to the eyes, particularly due to the effect of ultraviolet radiation.

The color of the lens or its degree of darkness does not necessarily correspond to an effective filter against UVA and UVB rays, so it is best to pay attention to the manufacturer's specifications, so that an aesthetic choice is also healthy.