It is undeniable that sunglasses are an accessory, in fact, both men and women choose them paying attention to the shape, the colors, the brand as well as how it is once worn. Less attention than what should be paid, however, to very important aspects for the health of the eyes, namely the type of sunscreen of the lenses. And instead, we should consider sunglasses a bit like sunscreen for the skin: a shield that protects us from the damage of solar radiation.
Why protect your eyes from the sun
In addition to burning the skin, UV radiation can cause damage to the visual system. Several studies tend to include very different pathologies such as cataracts, age-related macular degeneration, photokeratitis and pterygium among the problems connected to these radiations. That’s why according to ophthalmologists, sunscreens should always be prescribed to every person and the choice of the type of sunglasses should not be made only based on aesthetics. “Wrong or non-certified sunglasses – explains Luigi Mele, ophthalmologist surgeon, University of Luigi Vanvitelli – Naples and president of the Scientific Committee of the Salmoiraghi & Viganò Foundation – can reduce the visible light that reaches the eye, eliminating discomfort caused by glare, but does not cut the ultraviolet, thus paradoxically resulting more dangerous than the absence of any protection “.
What are glasses filters for
Not only creams have a sunscreen, but also glasses because this term refers to all means of protection, whether they are made of glass or organic material, which are able to absorb a part of the solar spectrum, visible or not. “The only way to protect the visual apparatus from the harmful effects of solar radiation – explains Mele – is to use sunglasses, equipped with sunscreens that must have three fundamental characteristics: 100% UV shielding, homogeneously all wavelengths and interfere as little as possible with the perception of colors. Only the use of certified materials and manufacturing processes can guarantee these characteristics and, consequently, adequate eye protection “.
The absorbent solar filter
There are different types of sunscreens: “There are absorbent filters that can have a uniform color over the entire surface or a shaded one-color or two-color tint,” explains Mele. How to choose between the two types? “A one-color gradient coloring can favor close-up vision for those who need to always wear colored lenses, for example those suffering from photophobia. This way when they look down to read they have a brighter image ”, Mele replies.
Reflective, polarizing and photochromic filters
But sunscreens can also be reflective when they protect the eye by reflecting unwanted radiation. “The reflectivity – explains the ophthalmologist –
depends on the surface coating of the lens. Mirrored lenses are part of this type of lenses. Polarizing filters, on the other hand, are used to select the radiation along the polarization axis, while photochromic filters are filters capable of varying the percentage of absorption based on the intensity of the radiation present.
The choice of color
Better not to be guided only by aesthetics, not even with regard to the choice of the color of the glasses. For those who see perfectly well, there is no particular color preference to respect and you can use all the filtering colors, brown, green, gray: “This last color – Mele specifies – has the property of attenuating radiation more uniformly. of all wavelengths, thus altering the natural chromatic perception of the environment to a lesser extent than other types of filters “. Those who, on the other hand, have any visual defects must pay attention. “For the farsighted, green or gray-green colored lenses are more suitable”, explains the expert, while a brown colored lens is recommended for the nearsighted.
The ‘classes’ of filters
The darker the filter, the more it protects in conditions of strong lighting but at the same time it can represent an obstacle when the radiation is suddenly reduced as it can happen while driving, when passing from a sunny area to a shaded area. Classes range from 0-1 when the filter is transparent, for closed environments and low light days, suitable for driving; class 2 for environments with medium lighting and cloudy days, only for daytime driving; class 3 dark for sunny days, only for daytime driving and 4 very dark for environments with strong lighting, such as in the high mountains, not suitable for driving. All sunglass lenses must have an indication of the filtering power on the label, from zero to 4.