Medicover
We wear sunglasses to protect ourselves from the sun's rays. When driving, sightseeing or relaxing at the beach, we put on sunglasses for our comfort. However, we should protect our eyes from the sun not only for the sake of comfort, but also for our health.
UVA and UVB radiation
UV, or ultraviolet radiation, is invisible to human eyes. One of its sources is the sun. There are three types of UV rays: UVA, UVB, and UVC, categorised according to the wavelength and the degree of risk to our health.
Of the three types of ultraviolet radiation, UVA has the greatest impact on human vision, explains optometrist Krzysztof Kluza. It is not blocked by the ozone layer and long-term exposure to it causes damage to the collagen fibres, which make up the cornea.
Absorbing UV radiation through the lens of the eye accelerates cataract development, leading to a gradual loss of vision and the need to surgically remove the opaque tissue. Cataract, unfortunately, is not the only eye disease that can be caused by the effects of sunlight.
When UV radiation reaches the bottom of the eye, it may cause damage to the extremely sensitive nervous tissue – the retina, especially within the macula, which helps us see the smallest details, says Krzysztof Kluza. We should also be aware that drying out the eye by the wind, combined with UV exposure (e.g. while sailing), may lead to irritation or even sunburn of the cornea.
The higher the sun is, the greater the exposure to UV radiation. This rule applies to the skin, not the eyes. Studies show that, paradoxically, at noon the risk to the eyes from UV radiation is lower, while it’s highest before and after noon. Why? This is due to the fact that when the sun is lower, it is closer to the line of our eyes, which makes them receive more rays. This is, of course, one of the factors that affect the degree of danger to our eyes.
What types of sunglasses are the best?
Many people believe that darker lenses offer better protection. Unfortunately, this is often not true. What's more, in some cases dark lenses can cause more harm than good. Why? Everything depends on how much they protect against UV rays. If dark sunglasses have no filter, or only have a UVB filter, they "trick" our pupils, which, when expanding, let in more UV rays. Therefore, it is worth investing in sunglasses with a filter. A UV-400 filter is enough, says Krzysztof Kluza.
The number indicates the range of radiation blocked by the glasses. In this case, the sunglasses will effectively protect us from radiation with a wavelength up to 400 nm, that is against UVA, as well as UVB and UVC radiation. Choose sunglasses that also protect your eyes from the sides. Many frames available on the market, although they have a high UV filter, block rays only from the front, leaving our eyes unprotected from the sides, he says.
Photochromic glasses
What other types of glasses (other than sunglasses) can we choose? One popular choice are photochromic glasses that are self-tinting when exposed to UV radiation and transition to clear lenses when indoors, says Krzysztof Kluza.
Unfortunately, they also transition to clear lenses inside cars (windows absorb UV rays), which is why for drivers I especially recommend polarising sunglasses, which reduce the glare from windows, surfaces, snow, ice and water. People who wear contact lenses should choose glasses that have a UV filter built into the fibre structure.
We should also remember that the effects of UV radiation accumulate throughout our lifetime, which is why it is so important to protect our eyes from an early age.
