THERE IS A FEW WHO PURCHASES DARK GLASSES TO HELP HEALTHY – they have long passed into the status of a fashion accessory : beautiful, comfortable, but as if not necessary at all. Sometimes we forget that we really need sunglasses: our eyes, like nothing else, need to be protected from rays, dust and other factors. We tried to figure out exactly how glasses protect the eyes and why low-quality glasses can even be dangerous.
Why is the sun dangerous to the eyes?
To understand why hide your eyes at all, you need to understand what shines in them – and what it threatens. The solar spectrum includes ultraviolet, visible and infrared radiation. Infrared does not harm the eyes, but ultraviolet and visible can be troublesome. Ultraviolet rays damage a variety of biological molecules, including protein and DNA. Damage to collagen (it is also a skin protein) accelerates the processes usually associated with aging – loss of elasticity and sagging, and if the DNA structure is disturbed, dangerous oncological diseases, including melanoma, can develop . This also applies to the eyes: risks associated with overexposure to sunlight include accelerated wear and tear on the central retina, leading to impaired vision, and even melanoma of the eye , a rare but fatal tumor that rapidly metastasizes and is currently incurable.
And that’s not all: ultraviolet light can lead to photokeratitis (inflammation of the cornea), snow blindness (burns of the conjunctiva and cornea), retinal burns (with significant dilation of the pupil behind dark lenses of glasses), solar retinopathy and dry eye syndrome. With regard to visible radiation, it (especially light in the blue spectrum) can impair visual acuity and provoke symptoms of visual fatigue – which is why when sitting at a computer, eyes often get tired. Finally, in certain sports, it is important that the goggles protect the eyes mechanically; if you suffer from seasonal allergies or you just have sensitive eyes, then you should protect them from pollen and dust.
It is simple to protect the skin from radiation – it is enough not to be lazy and use cosmetics with SPF all year round; eyes can only be saved by glasses with a high-quality filter that does not allow ultraviolet light to pass through. Most importantly, remember: dark does not mean sun protection. At the departments of ophthalmology, students are often told a story that happened in the eighties in Odessa: someone brought there a large batch of dark glasses without a UV filter, and it turned out that almost all of them went to taxi drivers. After a couple of weeks, they reached out to the ophthalmologists’ offices. The accessory did much more harm than good: the hapless taxi drivers suffered retinal burns. In the dark, the pupil dilates, so that much more sunlight gets on the retina than usual – and if we are talking about glasses without protection, then a sad fate awaits the eyes.
How can glasses help?
The lenses of quality glasses can be made of glass or polycarbonate; Each of these materials has advantages and disadvantages, but both, when properly manufactured, reliably block UV radiation. Glass is harder to scratch and is still the most transparent material known to mankind – which is why it is still used in microscopes, cameras or binoculars. On the other hand, the glass itself does not block UV-A radiation, so the glasses require additional coating; besides, glass glasses are heavy, fog up easily and can break.
Polycarbonate lenses are ten times stronger than glass or regular plastic, making them ideal for children and athletes; they are lighter and thinner than glass and block 100% of UV radiation. True, polycarbonate is easy to scratch and is not as transparent as glass – it happens that objects in such glasses do not seem clear enough. There are other materials for specialty goggles – for example, the impact-resistant Tribrid and Trivex, the lenses of which are inserted into goggles for skiing or snowboarding.
Additional UV protection is provided either by coating or by adding certain chemicals to glass or polycarbonate during the manufacturing phase. Although the material itself blocks ultraviolet light, tinted glasses are banally more comfortable for the eyes – so they get tired of the rays of the visible spectrum less. As common sense suggests, the darker the lenses, the more suitable they are for sunny days – and vice versa, yellow or pink glasses will be nice in cloudy or foggy weather.
How to choose the degree of protection?
Lenses are divided into five types according to the degree of protection: very light lenses transmit 80-100% of the light and are suitable for use in the city in cloudy weather (category 0-1), and dark lenses transmit only 3-8% of the light and can be used, for example, high in mountains (category 4). For travel to the sea, lenses that transmit 18–43% of the light (categories 2-3) are usually suitable. Glasses should be absolutely transparent, so that they can clearly distinguish objects at different distances. Good glasses always come with a label that indicates the percentage of UVA and UVB blocking and the category of protection. Sometimes it is indicated where the glasses can be used – in the city, at sea or in the mountains. It is important that you cannot drive a car with category 4 glasses – and this should also be written about.
There are photochromic lenses, which are also called “chameleons” – they react to the intensity of light and change the degree of dimming, becoming dark in bright sunlight and almost transparent in the room. However, such glasses need to be changed regularly, because the photochromic “agents” wear out quickly and the darkening becomes weak.
Is there a point in cheap glasses?
Unfortunately, it is almost impossible to check the authenticity of the UV protection in the display case with glasses – you just have to trust the label. It should indicate the presence of UVB and UVA blocking – however, an additional difficulty is that labeling standards are not mandatory, and it is up to the manufacturer to comply with them or not; even the FDA guidance is advisory. One exception is Australia and New Zealand, where sun exposure risks are taken especially seriously, and any sunglasses must be tested and labeled according to a mandatory standard.
Be that as it may, it is better to choose glasses on which the maximum degree of protection is indicated – for example, as a percentage (80-100%). Sometimes it is written on the label that glasses do not transmit light with a wavelength of up to 400 nm – this is equivalent to complete blocking. The European standard (CE) may also be indicated with the numbers 0, 2, 6 or 7, where 0 is zero protection, and 7 is full. If there is an ultraviolet lamp at home, then in the glasses you already have, you can carry out a simple test: shine a lamp through the glasses on banknotes. If the lens material is UV-resistant, you will not see watermarks.
A pleasant fact – even cheap glasses can provide high-quality protection from the sun if they are made of adequate materials and certified. It turns out that glasses from the mass market can be bought for eye protection, if you are sure of the quality of the glasses; it is the best choice for the beach – it will not be a pity to lose them or get scratched by the sand.