Sunglasses are not only an indispensable summer fashion accessory, but they are also essential for protecting your eyes from the harmful sun rays.
Especially in summer, when the opportunities to spend a very long time outdoors are greater and exposure to reflective surfaces (beaches, sea or meadows) is more likely, the eyes are strongly stressed and need special attention, like the skin in the sun.
The ANSI classifies sunglasses as an “individual protective device” (DPI). Ophthalmic lenses equipped with selective filters for ultraviolet (UV) rays, in fact, they have the function of protecting eye structures from the risks of solar radiation.
For this reason, sunglasses must be manufactured to perfection and meet pre-established safety and quality standards.
Why Do We Need Sunglasses?
Sunglasses provide essential protection to avoid compromising vision, as they shield ultraviolet (UV) radiation from the sun and reduce intense brightness, which is responsible for reduced visibility and various disorders such as eye irritation, eyelid dermatitis, conjunctivitis, and keratitis.
Ultraviolet rays also trigger excessive production of free radicals, responsible for aging cells and tissues (including eyes). Over time, this phenomenon can promote the progressive opacity of the lens (the structure that filters and projects light on the retina) from which cataract development can be achieved. Blue light - in the spectrum of the visible, bordering on UV rays - increases the risk of macular degeneration.
Things you should know about Ultraviolet radiation
The sunglasses are equipped with an anti-UV filter, capable of absorbing radiation of type A and B (UVA and UVB), which are more harmful to the eye than those of visible light.
Ultraviolet rays derive largely from the sun and include the portion of the electromagnetic spectrum with a wavelength of between 100 and 400 nanometers (nm).
UVA (315–400 nm): It is ultraviolet radiation that penetrates deep into the skin, promotes the release of the melanin from melanocytes and tan.
UVA poses a subtle threat: they are also present on days with overcast and cloudy skies and, unlike sunburn caused by UVBs, do not create particular discomfort and their impact can manifest itself even after years.
As for the eye, UVA can help determine the opacity of the crystalline (cataract), eyelid dermatitis, pterygia, conjunctivitis, and keratitis, while damage to the retina seems to be limited. The appearance of these issues is directly proportional to the frequency of exposure. The effect of UVA is reduced by sunglasses and is hampered by protective clothing and filters to be applied to the skin.
UVB (280–315 nm): They are potentially more harmful and carcinogenic than UVA, but they produce a stimulating action the neo synthesis of melanin and activate the metabolism of vitamin D. As with UVA, exposure to this type of solar radiation can predispose to the onset of various eye problems.
UVC (100–280 nm): These are the most dangerous radiations; Ortuunaly, however, this type of solar radiation is shielded from the ozone layer in the Earth’s atmosphere, so they do not generally reach the soil (most ultraviolet rays that reach the Earth’s surface are, in fact, UVA and, to a small extent, UVB).
If the eye were exposed to UVCs for too long, there would be problems concerning mostly and conjunctive.
UV: Factors that influence its threat
In general, the penetration capacity of UV, therefore their “dangerousness” increases as the wavelength decreases and, consequently, as the frequency increases.
Another detail not to be underestimated is that UV radiation is more intense:
As the altitude rises (every 1000 meters high, UV levels increase by 10–12%);
When the sun is close to astronomical noon, that is, it reaches the maximum height for the latitude at which you are;
As the cloudiness decreases.
Other environmental factors influencing UV levels are the ozone layer and the reflective capacity of the Earth’s surface.
How do Sunglasses work?
An ophthalmic lens works by essentially modifying the divergence of a beam of radiation; the filters with which they are made alter the energy composition preventing the passage of certain wavelengths or limiting the energy of them.
Sunglasses lenses are equipped with anti-UV filters that act to change the energy characteristics of ultraviolet radiation. These filters are sometimes added to UV protection coatings to block all radiation up to 400 nm.
The treatment does not result in loss of brightness: an absolutely transparent material can be “filtering” while acting on invisible wavelengths.
It should be known, in fact, that the screen against ultraviolet is not given by the color, but by the filtering power of the sunglasses, indicated with a number from 0 to 4 and affixed in the form of a mandatory sticker on the lens.
On the other, however, it is obvious that colored sunglasses (grey, brown, green, etc.) reduce color perception.
Risks for the Eyes
Sunglasses: Consequences of UV rays on the eyes
The conjuncture is the thin mucous membrane that covers the anterior surface of the eyeball (except the cornea) and the inner membrane of the eyelids. This structure can be affected by conjunctivitis, which can also be induced by exposure to the sun, especially in conditions of strong reverberation. Inflammation of the conjunctive involves redness, burning and swelling.
The cornea covers the front of the eye, through which you can catch a glimpse of the iris and pupil.
Transparent and avascular, this structure represents the first “lens” that light encounters in its path to the optical pathways. If you do not wear sunglasses, UV exposure can predispose you to keratitis, which manifests itself with burning, photophobia and the feeling of sand in your eyes.
The iris is a thin membrane, of variable color and of an angular shape, visible from the front through the transparency of the cornea. The lighter this part (blue, green or gray eyes), the greater the risk of manifesting sensitivity to sunlight (photophobia).
The cataract resulting from this process is usually age-related, although the causes may be different. In any case, the probability of the appearance of the senile form of the disease is directly related to the amount of sunlight to which it has been exposed over the course of life.
The retina is a tissue of nervous origin, covering almost the entire inner wall of the eye and helping to perform the first processing of the visual signal.
This delicate structure contains photoreceptors, lightwave sensitive cells: sticks and cones. The retina functions, therefore, as a photo transducer, that is, it captures the light stimuli and converts them into bioelectric signals, which in turn are sent to the brain through the fibers of the optic nerve.
The retina is susceptible mainly to UVA-induced damage: some scientific research associates sun exposure with the onset of maculopathy.
In particular, solar radiation demonstrated involvement in the induction or progression of retinal damage in cystoid macular edema, solar retinopathy (or epitheliopathy) and age-related macular degeneration.
Eyelids and Eye Contour
The eyelids are movable muscle-cutaneous folds, able to completely cover the front of the eyeball. Like other ancillary eye formations, they are protective by external agents and contribute to bulb support; The frequent winking of the eyelids also allows the continuous distribution of tear film on the eye surface.
The eyelids, as well as the skin of the eye contour, is very thin: from an aesthetic point of view, the sun promotes the formation of wrinkles and spots. It is not to be underestimated, then, that exposure not protected by sunglasses can increase the risk of skin cancers in the periocular area.
Sunglasses: What requirements should they meet?
All sunglasses must be labeled:
The filter power indication, from zero to 4: to choose sunglasses, keep in mind that the filter categories are:
(0-1) Category (transparent filter, very clear or clear): the filtering power is almost nil, the lens alone dims the brightness a little, so it is suitable for closed rooms and days with little lighting;
(2) Category (average filter): for medium lighting and cloudy days;
(3) Category (dark filter): for general use in full sun;
(4) Category (very dark filter): for strong lighting, high mountain, and reverberating surfaces.
Instructions for use, cleaning, and maintenance.
The filter power category of a lens does not provide information on the UVA and UVB protection of sunglasses. The latter is referred to by the acronym “UV” followed by the maximum frequency of filtered light, expressed in nanometers (nm). For example, UV 400 means that the lens is treated to absorb all ultraviolet frequencies up to 400 nm, hence both UVA rays and UVB rays.
The level of protection of these lenses is 99–100%. The acronym “UV” is found as a sticker on the lens and in the information note that certifies the quality data of the sunglasses.
The mark refers to the ANSI’s minimum standard of protection, so it is not a guarantee of eyeglasses quality on its own. In practice, it certifies that the lenses allow no more than 5% of UV rays to pass through. For this reason, it is also good to refer to the information manual attached to the sunglasses.
The marking can not be affixed on the lens as a sticker, except the size and shape of the glasses do not allow it; in that case, it must be shown on the packaging.
Types of Sunglasses
Polarized sunglasses are lenses equipped with polarizing (or polarizing filter) and sunscreens.
Polarizing filters act on visible radiation, modulating brightness and neutralizing reflections from smooth, shiny surfaces such as water, sand, snow, grass or asphalt. In addition to limiting the phenomenon of glare, polarized sunglasses protect eye structures from UV radiation.
Photochromatic sunglasses have the ability to darken in the sun and lighten in the dark, best adapting to different lighting conditions.
Degrading sunglasses are characterized by a progression of hue that allows modulating the light intensity, making them particularly suitable in the presence of certain retinal pathologies.
Camera Sunglasses are equipped with a camera to shoot video and photograph with the touch of a button. These have a built-in HD microphone and records sounds up to 20ft.
What kind of glasses matches your face?
The oval face is considered an ideal shape because it has balanced proportions. To maintain an oval natural balance, select frames that are as wide (or wider) as the widest part of the face, and are also good walnut-shaped frames that are not too deep or wide.
Triangular shape with base upwards
With this shape of the face, the upper part of the face is very wide, while the lower part is very narrow. To reduce the width of the upper face, try the frames that are spread to the bottom, lightweight or unframed glasses (which have a lightweight, airy effect).
An oblong face is longer with a pronounced beard line, sometimes a longer nose. To make an oblong face shorter and more harmonious, try the frames that go higher in-depth than in the width or low bridge of the glasses to shorten the nose.
A square face has a strong line of beard and a wide forehead that is the width and length of the same proportions. To make a square face look longer and softer, try the long frames, the frames that go more into the width than in the depth of the oval framework of the narrow proportions.
The diamond shapes of the face are narrow in the eye and beard line and have pronounced cheekbones that can look high and dramatic. This is the rarest form of a face. To highlight your eyes and soften your cheekbones, try out frames that have a pronounced line of eyebrows, spectacles without frames, oval or cat frames.
The round face has a rounded line of equal proportions of length and width, with no corners. To make the round face longer and narrowest, try the narrow square frames to lengthen the face, a clear bridge to highlight your eyes, and frames that are wider than longer, like rectangular shapes.
Triangular shape with base down
This shape of the face has a narrow forehead and spreads towards the cheeks and the area of the beard. To add width and emphasize the lower upper part of the head, try the frames that are quite pronounced, whether in color or detail, on the top half of the frame, and the macho shapes are also recommended.
What are the advantages of Sunglasses?
Sunglasses attenuate the effects of diffuse and often annoying radiation. As a result, the vision with sunglasses is clear and comfortable, especially in very bright outdoors. This feature is to be taken into account in the practice of recreational or outdoor sports activities (fishing, cycling, winter skiing, water sports, etc.) and in situations where it is necessary to protect yourself from the very intense sunlight or its reflection (sea, lake, snow, ice, sand, lawn and rivers).
Protect your eyes from UVA and UVB rays with the skin, excessive or unregulated exposure to sunlight can be harmful to vision. Glasses with sunglasses limit and prevent the harmful effects of this radiation.
The most exposed to the damage of the sun’s rays are children and the elderly, for whom it is necessary to choose glasses capable of breaking down both UV rays, and the so-called “blue light”, less known, but equally dangerous, co-responsible in determining both the opacity of the lens and maculopathy.
Increase in visual comfort
Uv filter lenses make vision more comfortable in environmental conditions where brightness is very intense. In sunny weather conditions, the result is a sharper and less tiring view for the eye. Sunglasses reduce eye fatigue, as sight is not forced to compensate for reflection and other phenomena resulting from bright light.
Sunglasses are essential for the well-being of the eyes in the city, high mountain, sea or, more generally, when practicing outdoor activities, where the reflection of light is very intense. Just think that the snow can reflect up to 85% of the light rays, the water 20% and the dry sand of the beach about 10%.
How to Choose the best pair of sunglasses?
Before buying a pair of sunglasses, the first rule not to forget is to always ask the opinion of your eye doctor. The specialist can indicate the type of lenses that are best suited for your needs, as well as provide practical and personalized advice about the correct ways of use and the occasions when it is contraindicated to wear them.
Details to watch out for in Sunglasses
Lenses with a filtered power of 0 absorb up to 20% of the radiation, so they are fine when the sky is overcast. 4-filter sunglasses absorb up to 97% of the light and are great on summer days and when you are at sea or in the mountains.
Those with light eyes (green, blue or gray) absorb more light radiation, so they should opt for lenses with a more filtering power than those with dark eyes (2 to 4).
When considering the purchase of sunglasses it is always good to take into account that the frame must be comfortable and compatible with the type of lenses chosen.
In addition, you should choose according to your needs and the use you intend to make: there are suitable sunglasses for the city and those most suitable for driving, for the sea and so on.
The general advice for the purchase of any type of eye care (from glasses to contact lenses) is to turn to a specialized optical center.
Sunglasses: How to choose a frame that fits your face?
One factor that has a big impact on the purchase of sunglasses is the design of the frame. In addition to personal aesthetic taste, however, it is good to keep in mind that the wide models, protect more, also covering the periocular area. Generally speaking, it is advisable to opt for more covering frames on days of intense sun, while the less extensive ones may be intended for the conditions of less radiation.
For sports practice (skiing, running, fishing, etc.) and activities that require maximum protection (e.g. hiking on a glacier) are indicated models of wraparound sunglasses.
What are sunglasses made of?
The frames are made from the most varied materials (metal, acetate, wood, etc.). Again, in addition to aesthetics, the practicality should be considered: in general, it is better to opt for light and durable sunglasses, which do not bother to carry them (which, among other things, would discourage its use of habitude).
As for lenses, the choice should be made according to the use to which the sunglasses are intended: glass glasses are heavier and more delicate, while the polycarbonate ones are light and easily portable. In the presence of a refractive vice (myopia, hyperopia, and astigmatism), it is possible to equip the correction lenses.
Don’t forget to protect children’s eyes from the sun: for them, there are frames and unbreakable fiber lenses.
How to protect your eyes from the sun?
The best strategy to protect your eyes is to avoid direct exposure as much as possible and always wear sunglasses when outdoors.
Wearing eye sunscreen throughout the year is a good habit. Although the sky is cloudy, the radiation is widespread and often annoying.
How to clean sunglasses?
To clean the lenses of the sunglasses you can opt for the use of microfiber cloths. These remove dust and moisture without scratching glasses or leaving halos.
However, avoid using handkerchiefs or shirt sleeves or paper for cleaning sunglasses because these will damage sunglasses by scratching them.
If sunglasses are among your favorite accessories, they require a minimum of thought before you go on the purchase.
The best way to find the glasses that fit you best is simply to try, so go for it! And have fun.