What material protects against ultraviolet radiation? Sun protection without harm to the skin - what is included in sunscreens. UV protection

With the onset of summer, the holiday season begins. A long-awaited vacation is most often associated with dreams of a picturesque seashore, bright sun and a bronze tan. However, the sun is not only a source of vitamin D, but also a factor that affects the body negative impact. Why is it necessary to protect your skin from ultraviolet radiation and how to do it? Let's take a closer look in the article.

What harm does ultraviolet radiation cause?

Ultraviolet radiation activates the aging process. Its effect often provokes burns, which prevent the reproduction of epidermal cells. The dermis becomes thinner, the content of collagen and elastic fibers in it decreases. The consequence of these processes is the appearance of wrinkles and premature aging (photoaging).

Women who live in the south age faster than women in the northern regions. This process also depends on the thickness of the skin. Women's skin is a third thinner than men's, so the fair sex develops wrinkles much faster. At the same time, brunettes are less susceptible to ultraviolet radiation than blondes. And those with fair skin and pregnant women are most likely to get sunburned when exposed to the sun.

Skin burns after sun exposure

But this is not the main danger. Ultraviolet radiation causes the main types of cancer:

Basal cell.
Squamous.
Melanoma.

It's not just sun exposure that poses a danger, but also tanning devices.

Ultraviolet Features:

More than half of UVA rays penetrate underwater to a depth of 0.5 m.
Sea foam can reflect up to a quarter of UV rays, dry sand - about 15%, snow cover - up to 80%!

How to protect your skin from ultraviolet radiation?

You can find out the UV index using mobile application. If the indicator is greater than 3, you must use a sunscreen with at least SPF 15. Not only sunscreens help protect your skin from harmful effects, but also clothing and sunglasses.

Cloth

Clothing made of thick fabrics and hats are the best protection from ultraviolet radiation. It is a common belief that only clothing made of light-colored fabrics prevents its effects on the skin. However, this is not true. Things white and yellow transmit UV rays. And wardrobe elements in dark blue and red cope much better with the task of protection.

The degree of protection is also affected by the material and type of fiber weaving. Thicker fabric transmits less ultraviolet radiation than thin fabric.

Things white transmits UV rays very well

Clothing has a UV protection factor - UPF. This parameter shows how many “units” of ultraviolet light will pass through the fabric. If the UPF is 40, then out of 40 only one unit will reach the skin.

Protective factors for natural fabrics:

Natural white linen - 10 UPF.
Dark linen, dyed with natural dyes - more than 50 UPF.
Factory-made items made of white cotton - 4 UPF.
Cotton fabrics dyed with natural dyes in green, brown and beige color, - from 46 to 65 UPF.

Items made using synthetic dyes, wet cotton, and silk do not protect against ultraviolet radiation.
To increase the degree of protection for cotton, use liquid detergent. It contains optical brightener, which increases the level of protection with each subsequent use. But using chlorine is not recommended - bleach is not optical, so it reduces protection.

Another way to increase the rate is to use a laundry detergent additive. It increases UPF from 5 to 30%.

Particular attention should be paid to the choice of summer clothes. Of course, a swimsuit and a T-shirt will not protect you from exposure to the sun's rays. Trousers, clothes with long sleeves and a closed neckline will cope much better with this task. An alternative is models with ultraviolet protection produced by sports brands. These are products made from synthetic fibers that are comfortable to swim in. They dry quickly and wick away sweat.

Manufacturers of clothing that protect against ultraviolet light say they conduct tests simulating two years of use: sun exposure, washing, wear and tear. They indicate the lowest result among the testing indicators. It is easy to find such clothing - it is labeled Sun Guard or Rash guard.

When in the sun, do not forget about your hat. Cap, Panama hat, scarf - there are plenty of options. But wide-brimmed hats do the best job of protecting the face, head, neck, and ears in the summer.

Glasses are an important summer accessory. They provide 100% eye protection from ultraviolet rays. But only models with the following labels have these properties:

Blocks at least 80%UVB, 55%UVA.
General, High UV protection.
UV 400 is an indicator of the length of rays that are not transmitted by lenses.

The numbers indicated on the glasses must be greater than 50.

Reliable eye protection against ultraviolet rays

UV protection products

Sunscreen for face and body is a controversial product. Higher SPF values do not provide more protection. The value indicated on the packaging is an indicator of the protection time. Calculate relative without dangerous time Sun exposure can be achieved by multiplying the SPF by the number of minutes it takes for the skin to burn in the sun.

Use sunscreens with caution

The SPF indicator affects the amount of UVB rays absorbed:

SPF 15 - 93%.
SPF 30 - 97%.
SPF 50 - 98%.

However, you shouldn’t rely on sunscreen alone. Manufacturers claim that it is impossible to fully comply with all test conditions so that the indicator corresponds to the number on the label.

Another controversial indicator is water resistance. In salt water, the cream is washed off in an average of 40 minutes. Some manufacturers indicate other indicators on the packaging.

The composition deserves special attention. Extracts of licorice, chamomile, aloe, allantoin and other substances that have an anti-inflammatory effect reduce painful sensations and redness. The effect lasts for six hours. They allow you to stay in the sun longer, which increases your risk negative impact ultraviolet.

Very little is known about nanofilters. They penetrate the body, but at the same time provide a balance between protection from two types of ultraviolet radiation and do not form free radicals under its influence. Main disadvantage physical filters - reducing the degree of protection of Avobenzone.

Sunscreen is applied to exposed areas in the ratio of half a teaspoon per 2 cm2 of skin. However, in large quantities, titanium dioxide is a carcinogen, so the recommended standards should not be violated. It is better to avoid using sprays. It is impossible to apply them in an even thick layer.
Chemical filters in sunscreens have a negative impact on endocrine system. According to a 2010 study from the University of Zurich, 85% of milk samples from Swiss mothers contain 1 cream “chemical.”

Main filters:

Oxybenzone. Contains in 70% of products. Patented as able to reduce skin redness after sunbathing. Its disadvantages: penetrates into milk, acts as an estrogen, is associated with endometriosis, alters thyroid hormones, is an allergen.
Octinoxate. A filter that penetrates milk. Animal experiments have shown that it has hormone-like activity in reproductive system And thyroid gland, and also causes allergies.
Homosalate. Damages estrogens, androgens, progesterone. When decomposed, it forms toxic products. Penetrates into milk.
Avobenzone. The best UFA filter, but unstable in sunlight if the cream does not contain Octisalate.
Mexoryl SX. Excellent protection against UFA. Stable and safe.

What else is included in sunscreens:

Methylisothiazolinone, or MI (preservative). American society contact dermatitis recognized it as “Allergen of the Year - 2013”.
Vitamins. A (retinol palmitate) - accelerates the development of skin tumors when applied to the skin in sunlight. Products containing this vitamin are not recommended for pregnant or breastfeeding women. Vitamins A, C and E are unstable when heated and long-term storage, so sunscreen cannot be used next season.

Research into sunscreens continues. Despite the fact that cream is the most convenient way to protect against ultraviolet radiation, it must be used with caution.

You can't see, hear, or feel ultraviolet radiation, but you can actually feel its effects on your body, including your eyes.

You probably know that excessive ultraviolet exposure increases the risk of skin cancer, and you try to use protective creams. What do you know about protecting your eyes from UV radiation?
Many publications in professional publications are devoted to the study of the effects of ultraviolet radiation on the eyes, and from them, in particular, it follows that long-term exposure to it can cause a number of diseases. In the context of a decrease in the ozone layer of the atmosphere, the need for the correct selection of means of protecting the organs of vision from excess solar radiation, including its ultraviolet component, is extremely urgent.

What is ultraviolet?

Ultraviolet radiation is invisible to the eye electromagnetic radiation, occupying the spectral region between visible and x-ray radiation within wavelengths of 100-380 nanometers. Entire region ultraviolet radiation(or UV) is conventionally divided into near (l = 200-380 nm) and far, or vacuum (l = 100-200 nm); Moreover, the latter name is due to the fact that the radiation of this area is strongly absorbed by air and is studied using vacuum spectral instruments.

Rice. 1. Full electromagnetic spectrum of solar radiation

The main source of ultraviolet radiation is the Sun, although some sources of artificial lighting also have an ultraviolet component in their spectrum; in addition, it also occurs during gas welding work. The near range of UV rays, in turn, is divided into three components - UVA, UVB and UVC, which differ in their effect on the human body.

When exposed to living organisms, ultraviolet radiation is absorbed by the upper layers of plant tissue or the skin of humans and animals. Its biological action is based on chemical changes in biopolymer molecules caused both by their direct absorption of radiation quanta and, to a lesser extent, by interaction with the radicals of water and other low-molecular compounds formed during irradiation.

UVC is the shortest wavelength and highest energy ultraviolet radiation with a wavelength range from 200 to 280 nm. Regular exposure of living tissue to this radiation can be quite destructive, but fortunately it is absorbed by the ozone layer of the atmosphere. It should be taken into account that it is this radiation that is generated by bactericidal ultraviolet radiation sources and occurs during welding.

UVB covers the wavelength range from 280 to 315 nm and is medium-energy radiation that is hazardous to human vision. It is UVB rays that contribute to tanning, photokeratitis, and in extreme cases, cause a number of skin diseases. UVB radiation is almost completely absorbed by the cornea, but some of it, in the range of 300-315 nm, can penetrate the internal structures of the eye.

UVA is the longest wavelength and least energetic component of UV radiation with l = 315-380 nm. The cornea absorbs some UVA radiation, but most of it is absorbed by the lens. This is the component that ophthalmologists and optometrists should primarily take into account, because it is the component that penetrates deeper into the eyes than others and is potentially dangerous.

The eyes are exposed to a fairly wide range of UV radiation. Its short-wavelength part is absorbed by the cornea, which can be damaged by prolonged exposure to radiation waves with l = 290-310 nm. As ultraviolet wavelengths increase, the depth of its penetration into the eye increases, and most of this radiation is absorbed by the lens.

The lens of the human eye is an excellent filter created by nature to protect the internal structures of the eye. It absorbs UV radiation in the range of 300 to 400 nm, protecting the retina from exposure to potentially harmful wavelengths. However, with long-term regular exposure to ultraviolet radiation, damage to the lens itself develops; over the years, it becomes yellow-brown, cloudy and, in general, unsuitable for functioning for its intended purpose (that is, cataracts form). In this case, cataract surgery is prescribed.

Light transmission of spectacle lens materials in the UV range.

Eye protection is traditionally carried out using sunglasses, clips, shields, hats with visors. Ability spectacle lenses filtering out potentially dangerous components of the solar spectrum is associated with the phenomena of absorption, polarization or reflection of the radiation flux. Special organic or inorganic materials are introduced into the material of spectacle lenses or applied as coatings to their surface. The degree of protection of spectacle lenses in the UV region cannot be determined visually based on the shade or color of the spectacle lens.

Rice. 2. Ultraviolet spectrum

Although the spectral properties of spectacle lens materials are regularly discussed on the pages of professional publications, including Veko magazine, there are still persistent misconceptions about their transparency in the UV range. These incorrect judgments and ideas find their expression in the opinions of some ophthalmologists and even spill out onto the pages of mass publications. Thus, in the article “Sunglasses can provoke aggressiveness” by consultant ophthalmologist Galina Orlova, published in the St. Petersburg Vedomosti newspaper on May 23, 2002, we read: “Quartz glass does not transmit ultraviolet rays, even if it is not darkened. Therefore, any glasses with glass spectacle lenses will protect your eyes from ultraviolet radiation.” It should be noted that this is absolutely false, since quartz is one of the most transparent materials in the UV range, and quartz cuvettes are widely used to study the spectral properties of substances in the ultraviolet region of the spectrum. In the same place: “Not all plastic eyeglass lenses will protect against ultraviolet radiation.” We can agree with this statement.

In order to finally clarify this issue, let us consider the light transmission of basic optical materials in the ultraviolet region. It is known that the optical properties of substances in the UV region of the spectrum differ significantly from those in the visible region. Characteristic feature is a decrease in transparency with decreasing wavelength, that is, an increase in the absorption coefficient of most materials that are transparent in the visible region. For example, ordinary (non-spectacle) mineral glass is transparent at wavelengths above 320 nm, and materials such as uviol glass, sapphire, magnesium fluoride, quartz, fluorite, lithium fluoride are transparent in the shorter wavelength region [BSE].

Rice. 3. Light transmission of spectacle lenses made of various materials
1 - crown glass; 2, 4 - polycarbonate; 3 - CR-39 with light stabilizer; 5 - CR-39 with a UV absorber in the polymer mass

In order to understand the effectiveness of protection from UV radiation of various optical materials, let us turn to the spectral light transmission curves of some of them. In Fig. the light transmission in the wavelength range from 200 to 400 nm is presented for five spectacle lenses made of various materials: mineral (crown) glass, CR-39 and polycarbonate. As can be seen from the graph (curve 1), most mineral spectacle lenses made of crown glass, depending on the thickness at the center, begin to transmit ultraviolet light at wavelengths of 280-295 nm, reaching 80-90% light transmission at a wavelength of 340 nm. At the border of the UV range (380 nm), the light absorption of mineral spectacle lenses is only 9% (see table).

Material	Indicator refraction	Absorption UV radiation,%
CR-39 - traditional plastics
CR-39 - with UV absorber
Crown glass
Trivex
Spectralite
Polyurethane
Polycarbonate
Hyper 1.60
Hyper 1.66

This means that mineral spectacle lenses made from regular crown glass are not suitable for reliable protection from UV radiation, unless special additives are added to the batch for glass production. Crown glass spectacle lenses can only be used as sun filters after applying high-quality vacuum coatings.

The light transmittance of CR-39 (curve 3) corresponds to the characteristics of traditional plastics, for many years used for the production of spectacle lenses. Such spectacle lenses contain a small amount of light stabilizer that prevents photodestruction of the polymer under the influence of ultraviolet radiation and atmospheric oxygen. Traditional spectacle lenses made of CR-39 are transparent to UV radiation from 350 nm (curve 3), and their light absorption at the boundary of the UV range is 55% (see table).

We would like to draw the attention of our readers to how much better traditional plastics are in terms of UV protection compared to mineral glass.

If a special UV absorber is added to the reaction mixture, then the spectacle lens transmits radiation with a wavelength of 400 nm and is an excellent means of protection against ultraviolet radiation (curve 5). Spectacle lenses made of polycarbonate are distinguished by high physical and mechanical properties, but in the absence of UV absorbers they begin to transmit ultraviolet radiation at 290 nm (that is, similar to crown glass), reaching 86% light transmission at the boundary of the UV region (curve 2), which makes them unsuitable for use as a UV protection agent. With the introduction of a UV absorber, spectacle lenses cut off ultraviolet radiation down to 380 nm (curve 4). In table 1 also shows the light transmission values of modern organic spectacle lenses made of various materials - highly refractive and with average refractive index values. All these spectacle lenses transmit light radiation starting only from the edge of the UV range - 380 nm, and reach 90% light transmission at 400 nm.

It must be taken into account that a number of characteristics of spectacle lenses and design features of frames affect the effectiveness of their use as means of UV protection. The degree of protection increases with increasing area of the spectacle lenses - for example, a spectacle lens with an area of 13 cm2 provides 60-65% degree of protection, and with an area of 20 cm2 - 96% or even more. This occurs by reducing side illumination and the possibility of UV radiation entering the eyes due to diffraction at the edges of spectacle lenses. The presence of side shields and wide temples, as well as the choice of a more curved frame shape that matches the curvature of the face, also contribute to increasing the protective properties of glasses. You should be aware that the degree of protection decreases with increasing vertex distance, since the possibility of rays penetrating under the frame and, accordingly, getting into the eyes increases.

Cutting limit

If the cutoff of the ultraviolet region corresponds to a wavelength of 380 nm (that is, light transmission at this wavelength is no more than 1%), then why do many branded sunglasses and spectacle lenses indicate a cutoff of up to 400 nm? Some experts argue that this is a marketing technique, since providing protection above the minimum requirements is more popular with buyers, and the “round” number 400 is remembered better than 380. At the same time, data has appeared in the literature about potentially dangerous influence light from the blue region of the visible spectrum to the eyes, which is why some manufacturers have set a slightly larger limit of 400 nm. However, you can rest assured that 380 nm protection will provide you with sufficient UV protection to meet today's standards.

I would like to believe that we have finally convinced everyone that ordinary mineral spectacle lenses, and even more so quartz glass, are significantly inferior to organic lenses in terms of ultraviolet cutting efficiency.

Prepared by Olga Shcherbakova, Veko 7/2002

How does sun clothing work?

The term “sun protective clothing” first appeared in 1996, when Australian companies, concerned about the high incidence of skin cancer on the continent, began developing specialized clothing with an additional level of UPF filters. Its peculiarity is that it should protect against ultraviolet rays of groups A and B (unlike conventional cosmetic sunscreens, which only resist UVB radiation), minimizing their negative impact on the skin. The level of UPF protection of such clothing usually varies from 15 to 50 - this is often achieved by treating the fabric with a special chemical composition(such as titanium dioxide) or ultraviolet block dye, which help absorb or reflect solar radiation. In addition, there are various laundry additives - powders, gels - that promise to turn any item of clothing into sun-protective clothing, giving it an additional UPF level.

Who needs it?

By and large, everyone. Even if you are not inclined to allergic reaction in the sun and do not plan to spend a vacation near the equator, additional skin protection from harmful radiation won't hurt. But for most of us, ordinary clothing is still enough, but specialized clothing, with a UPF factor, is intended more for people with disabilities. hypersensitivity skin and for those who have to spend a long time in extreme conditions under the scorching sun. In addition, many experts call for choosing clothes with additional UPF protection for children - the reasons for this are obvious.

Jason Briscoe/Unsplash

What, regular clothes won't do?

As already said, most people really don’t think about clothes with special UPF filters, limiting themselves to ordinary sunscreens and basic principles like “covering your shoulders on the beach.” For example, the UPF level of a regular cotton T-shirt is on average 5-8, that is, it transmits about one-fifth of UV rays. Let us repeat: if you do not have a critical need for serious measures, it is not necessary to update your wardrobe with items marked UPF block.

Any clothing provides us with additional protection from solar radiation, so it’s enough just to remember a few basic rules. So, the denser the fabric fibers, the higher the level of protection: for example, artificial lycra, polyester, nylon or acrylic cope with this task better than thin natural cotton or weightless linen, but they are also less comfortable for hot weather. A simple test: the more see-through the fabric is, the weaker its UPF function. Therefore, if you are not ready to wear synthetics in the heat (although some of its modern representatives are quite suitable for such conditions), choose unbleached cotton and linen with the most dense thread arrangement.

By the way, one more important point- almost all fabrics lose their UPF properties by an average of 50% when wet (the exception is silk and viscose, here the situation is the opposite). The color of the item also plays a role - clothes in dark shades absorb UV radiation more effectively, the same goes for bright, saturated colors in comparison, for example, with pastels. And lastly, the most obvious: what larger area covering the body with clothing, the higher the degree of protection, so the ideal option for walking under the scorching sun would be, say, a suit of a tunic with long sleeves and loose-fitting trousers. And a wide-brimmed hat, of course.

Where to buy “sun clothing”?

For many people, sunglasses are an everyday accessory that allows them to highlight their style and create the desired look. However, we should not forget that these optical products perform another important function- eye protection from ultraviolet radiation. Let's consider what determines the degree of blocking of UV radiation in sunglasses.

Currently, the ophthalmic products market offers a wide selection of sunglasses. The assortment is replete with popular brands, a variety of shapes, designs and colors. However, when purchasing eyeglass optics, you need to take into account not only the decorative component, but also the protective properties of the lenses. It is important that the correction agent provides required level protection of the organs of vision from the harmful effects of ultraviolet rays.

Many people are interested in how to choose sunglasses based on the type of protection. We suggest you look into this issue.

Should you protect your eyes from ultraviolet radiation?

To understand whether it is worth protecting your eyes from exposure to sunlight, you need to understand their types, the nature of their occurrence and the impact on the human visual organs. Up to 40% of radiation is classified as visible and allows us to distinguish colors. About 50% of the sun's rays are infrared. They allow you to feel warmth. Finally, 10% of the sun's rays are ultraviolet radiation, which is invisible to human eyes. According to the wavelength, it is divided into several subcategories (long wavelength - UVA, medium wavelength - UVB, and short wavelength - UVC).

Types of ultraviolet radiation:

UVA - is in the range of 400-315 nm. Mainly reaches the surface of the Earth;
UVB - is in the range of 315-280 nm. Mainly retained by the atmosphere, but partially reaches the Earth's surface;
UVC - is in the range of 280-100 nm. It practically does not reach the surface of the Earth (it is retained by the ozone layer).

Do you need glasses to protect your eyes from UV rays?

Ophthalmologists say that in moderate quantities, ultraviolet light is beneficial for the body, as it helps strengthen the immune system, improve body tone and even improve mood. Under the influence of UV rays in the eye, metabolism and blood circulation are stimulated, and muscle function is improved. In addition, the body produces vitamin D, which strengthens musculoskeletal system, and histamine is produced, a substance that has a vasodilator effect.

However, with intense exposure, ultraviolet rays have a detrimental effect on the body, including the organs of vision. The lens captures long-wave UV radiation, gradually losing transparency and acquiring a yellowish tint. Experts recommend paying due attention to protecting your eyes from ultraviolet radiation, since clouding of the lens leads to the development of such a serious disease as cataracts. In 50% of cases, in the absence timely treatment this eye disease is a cause of blindness. The mucous membrane of the eye and the cornea absorb mid-wave ultraviolet radiation (UVB), which can significantly damage their structure with intense exposure. Using sun protection accessories avoids this problem.

To make a smart purchase, you need to decide what kind of UV protection your sunglasses should have. This factor should be given primary attention when purchasing these products.

Why you should protect your eyes from intense ultraviolet radiation:

The lens captures long-wave UV radiation, gradually losing transparency and acquiring a yellowish tint. This can lead to cataracts;
The cornea absorbs mid-wave ultraviolet radiation (UVB), losing its optical properties.

What kind of protection should sunglasses have?

Many people do not know how to determine the level of protection of sunglasses and mistakenly believe that the darker the lenses, the better they block UV rays. However, this is not true. Clear lenses can absorb harmful radiation just as well as dark lenses if a special coating is applied to their surface. Moreover, the pupil dilates under dark lenses, so in the absence of a filter, ultraviolet rays are easily absorbed by the lens.

Products from world-famous brands must have special markings indicating the degree of protection. Spectacle optics marked “UV400” are considered to be of the highest quality. It filters up to 99% of UVA ultraviolet light with a wavelength of up to 400 nm. However, it should be taken into account that when regularly wearing such glasses in the summer, a “mask” is formed on the face, since the skin around the eyes does not tan. Much more common are products labeled UV 380, which filter only 95% of UV rays. Inexpensive products provide blocking of 50% of radiation. All products that capture less than 50% of ultraviolet rays do not protect the eyes from their negative effects. Often they are used only for decorative purposes.

Sometimes there is a marking that indicates the degree of protection from both UVA and UVB rays: “Blocks at least 80% UVB and 55% UVA.” This means that the filter applied to the surface prevents the penetration of up to 80% of UVB rays and up to 55% of UVA rays. Doctors advise choosing products where both indicators are above 50%.

In addition, there is another option for marking glasses:

Cosmetic. Optical products that block less than 50% of UV radiation. These glasses are not recommended for use on sunny days, as they do not protect the eyes from the sun;
General - universal products with UV filters that block from 50 to 80% of UV rays. Such glasses can be used for everyday eye protection in the city, at mid-latitudes;
High UV-protection - models with enhanced UV filters that block almost 99% of ultraviolet radiation. They can be used on a bright sunny day in the mountains, near the water, etc.

How to choose sunglasses based on darkness?

Once you have decided on the degree of protection of your glasses from exposure to ultraviolet radiation, you need to select their level of light transmission, or darkness. This parameter will determine how brightly you can perceive the world around us. Typically, this marking is located on the temple of the glasses and consists of two components: the model name and the darkness rating, for example, “Cat. 3" or "Filter cat. 3".

Classification of sunglasses by darkness:

Marking (0). These products are almost completely transparent. It transmits from 80 to 100% of visible sunlight. These glasses are recommended for use by athletes when exercising in the absence of bright light.
Marking (1,2). This optics has light transmission from 43 to 80%, and from 18 to 43% of light, respectively. This best option for wearing in low to medium sunlight.
Marking (3,4). These glasses should be used in very bright sunshine.

In the hot summer, for our latitudes, the optimal choice would be optical products with 2 and 3 degrees of light transmittance. For use on summer mornings, as well as in spring and autumn, models with 1-2 degrees of darkening are suitable. Glasses with index 4 are recommended for travelers to wear in extreme conditions, for example, when conquering mountains.

It should be clarified once again that the degree of darkness has nothing to do with protecting the eyes from the adverse effects of ultraviolet rays. This indicator exclusively affects the brightness of image perception and the wearing comfort of optical products.

What other protection could glasses have?

Modern manufacturers of sunglasses make sure that their products are as comfortable, practical and durable as possible to use. Therefore, in addition to an ultraviolet filter, additional coatings are often applied to the surface of products.

Polarizing filter. Completely blocks glare - rays reflected from horizontal surfaces (water, snowy field, car hood, etc.);
Anti-glare coating. Cuts off some types of solar glare, increasing comfort of use;
Mirror coating. As a rule, it is applied to one degree or another on all glasses. Reflects visible sunlight, providing additional comfort to the eye;
Abrasion resistant coating. Increases the resistance of spectacle lenses to the appearance of mechanical damage(scratches, cracks, etc.);
Melanin coating. Apply to inner side lenses to prevent eye fatigue.
Gradient coating. Allows you to increase safety while driving. The upper, darker part of the lenses provides good visibility when looking at the road. In turn, the light bottom of the lenses contributes to good review dashboard.

We recommend that you familiarize yourself with the wide selection of glasses and contact correction products on the website. We offer you high-quality products from world brands at competitive prices. With us you can easily place an order and receive the goods in the shortest possible time!

Visible radiation - electromagnetic waves, perceived by the human eye, are approximately in the wavelength range from 380 (violet) to 780 nm (red). What is to the right of the visible spectrum, i.e. with a wavelength of more than 780 nm is infrared (IR) radiation, invisible to humans. To the left, i.e. with a wavelength from 250 to 400 nm, there is that part of the spectrum invisible to humans that interests us today - ultraviolet (UV). Exposure to ultraviolet radiation (UV) affects the eyes, skin and immunity. In ordinary life, straight sun rays do not reach the eyes, especially when the sun is at its zenith, but due to reflections from surfaces, it is believed that 10-30% of radiation (depending on external conditions), reaching the surface of the earth, eventually gets into the eyes. In the case of paragliders, when pilots have to raise their heads towards the sun, direct rays also hit them. For winter sports (skis, snowboarding, kite, etc.), as well as for water activities (kite, surfing, beaching, etc.), the amount of reflected radiation entering the eye is greater than average.

Based on wavelength, UV radiation is divided into 3 components: UVA, UVB and UVC. The shorter the wavelength, the more dangerous the radiation. UVC, the shortest wavelength and most dangerous range of ultraviolet radiation, fortunately does not reach the earth's surface thanks to the ozone layer. UVB – radiation in the range of 280-315 nm. Approximately 90% of UVB is absorbed by ozone, as well as water vapor, oxygen and carbon dioxide when passing sunlight through the atmosphere before reaching the earth's surface. UVB in small doses causes a tan, in large doses it burns and increases the chances of skin cancer. Excessive exposure of the eyes to UVB rays causes photokeratitis ( sunburn cornea and conjunctiva, which can lead to temporary loss of vision (severe photokeratitis is often called “snow blindness”). The risk of photokeratitis increases at high altitudes, as well as in snow, if the eyes are not protected from ultraviolet radiation. Note that the effect of ultraviolet radiation in the UVB range is limited to the surface of the eye; these ultraviolet rays practically do not penetrate into the eye.

Ultraviolet radiation in the UVA range (315-400 nm) is close to the visible spectrum, and in the same doses is less dangerous than UVB radiation. But these ultraviolet rays, unlike UVB, penetrate deeper into the eye, damaging the lens and retina. Exposure to UVA in the eyes over a long period of time increases the risk of a number of dangerous diseases eyes, including cataracts and macular degeneration, which is considered the leading cause of blindness in old age. Well, let’s mention the part of the visible spectrum corresponding to the blue rays of the visible spectrum, about 400 -450 nm, (HEV “high-energy visible light”), which are directly adjacent to the long-wave part of the UV range. Long-term exposure to these high-energy visible rays is also thought to be harmful to the eyes because they penetrate deep into the eye and affect the retina.

The damaging effect of ultraviolet rays on the eyes depends on a number of factors:

Duration of stay outdoors
Geographic latitude of the location. The most dangerous zone is the equatorial zone
Altitude. The higher, the more dangerous
Time of day. The most dangerous time is from 10-11 a.m. to 2-4 p.m.
Large surfaces of water and snow that highly reflect the sun's rays

Thus, constant exposure to ultraviolet radiation on the eyes has a harmful effect on the surface of the eye and its internal structures. Moreover, negative effects have the ability to accumulate: the longer the eyes are exposed to the damaging effects of ultraviolet radiation, the higher the risk of developing pathologies of the eye structures and age-related diseases of the organ of vision.

Sunglasses are one way to limit the amount of harmful radiation reaching your eyes. Since lifetime doses ultraviolet irradiation accumulate, increasing the risk of eye diseases, it is recommended to regularly use sunglasses outdoors.

Measurements and results

Lens characteristics and concepts that we will need when analyzing tests and measurements: Optical density. This is the decimal logarithm of the ratio of the intensity of the incident radiation to the transmitted radiation. D=lg⁡(Ii/Io) That is if the optical density of the lens is 2, then it reduces the radiation intensity by 100 times, blocking 99% of the incident radiation. If D=3, then the lens blocks 99.9% of the radiation. In addition, sunglasses lenses are divided according to their transparency (for the visible spectrum):

Transparent F0, 100 - 80% light transmission used in twilight or at night, sports and safety glasses against snow and wind;
Light F1, 80 - 43% light transmission, glasses for cloudy weather;
Medium F2, 43 - 18% light transmission, used in partly cloudy weather;
Strong F3, 18 - 8% light transmittance, for protection from bright daylight;
Maximum strong F4, 8 - 3% light transmission, for maximum protection in high altitude conditions, at ski resorts, in the snowy arctic in summer. Not intended for driving a car.

For measurements we have a spectrophotometer:

We selected several glasses and lenses from different manufacturers at completely different prices. The cost of glasses ranged from 1 to 160 Euros (70 -11,000 rubles). So, let's start from expensive to cheap: The first 2 lenses are GloryFy, brown F2 and gray F4. Glasses of this brand with such lenses cost approximately 11,000 rubles.

Transmission graph in %, i.e. what percentage is the intensity of the transmitted radiation from the incident one:

Red shows the transmission of the brown F2 lens, and blue shows the transmission of the gray F4 lens. As can be seen from the graphs, both lenses cut all ultraviolet light well. In addition, it is clear that the brown F2 lens cuts the blue part of the spectrum much better, the gray F4 is essentially neutral (i.e. does not distort colors) and, being darker (F4 versus F2 for the brown one), darkens more strongly throughout the entire spectrum. For a more accurate assessment of how well ultraviolet radiation is blocked, here is a graph of the optical density for these lenses:

the red line is for the brown lens F2, and the blue line is for the gray lens F4

It can be seen that the optical density is greater than 2.5 over the entire ultraviolet range, i.e. More than 99% of ultraviolet light incident on the lens is blocked. To clarify, I will give the values for these lenses for a wavelength of 400 nm. Optical density for gray F4 D=3.2, for brown F2 D=3.4. Or the transmittance from the incident radiation for gray F4 is 0.06%, and for brown F2 it is 0.04%.

Let's move on. Here we present graphs of transmittance and optical density for glasses in the middle price category: Smith and Tifosi - both lenses are gray, dark. The cost of glasses is about 4000-6000 rubles. And cheap glasses costing about 700 rubles - 3M and Finney - both lenses are also neutral, i.e. gray, dark. For starters, the transparency for all these mentioned lenses

From the graphs it can be seen that all lenses are category F3. In addition, it is noticeable that the lenses of cheap glasses (3M and Finney) are worse at cutting near ultraviolet light, UVA in the range of 385-400 nm. Now for all these 4 points we give the transmittance value at a wavelength of 400 nm:

Smith T=0.002%
Tifosi T=0.012%
Finney T=5.4%
3M T=9.4% and optical density at the same wavelength:
Smith D=4.8
Tifosi D=3.9
Finney D=1.26
3M D=1.02

It is clearly visible that cheap 3M and Finney glasses do not meet the UV400 protection requirements. They begin to protect normally from wavelengths of 385 nm and below.

But we have the cheapest glasses, unbranded (Auchan glasses). Cost 70 rubles or 1 euro. The lens is yellow, the transmission seems to be F1 category. Transparency:

Optical Density:

For a wavelength of 400 nm, the transmittance was 0.24% and the optical density was 2.62. This lens meets the UV400 requirement.

Conclusions:

It is clear that cheap glasses do not have a stable quality of protection: 2 out of 3 samples were not satisfactory. Branded glasses of the upper and middle price categories did a good job of protecting against ultraviolet radiation. In addition, when we talk about protection from ultraviolet radiation with glasses, we should take into account that light can also penetrate from the side of the frame, so, of course, glasses that cover the entire field of view and do not allow light to enter the eyes past the lenses of the glasses are better protected. And of course, when choosing glasses, you should consider how comfortable they sit on your face, because you have to wear them for hours. For people involved active species sports and frequent travelers, it is important how durable the glasses are: it’s unpleasant to find fragments in your backpack at the right time instead of glasses.