Sunglasses are not only cool , but also a must-have item. In the face of all kinds of sunglasses, are you tangled? Style, in fact, is only the last consideration. How to choose, there is some knowledge.
In summer, the sun is dazzling. Invisible ultraviolet light makes people have nowhere to hide. Most people know that excessive ultraviolet radiation can damage the skin. However, that many people didn't expect is that UV can also damage our eyes, and even cause cataracts, burns and even cancer in serious cases.
UV damage to eyes
According to the wavelength, UV can be roughly divided into UVA, UVB and UVC. Among them, UVC can only reach the ozone layer, and UVA and UVB can penetrate the ozone layer, directly to the eyes.
UVB can shine on the lens of the eye, but UBA can shine further to the retina of the eye.
The main damage to the eyes caused by excessive ultraviolet radiation is cataract, macular degeneration, skin lesions around the eyes and even cancer.
Cataracts
Cataracts are the main cause of vision loss or blindness in people over 40 years old. The crystal of normal eyes is clear. If the crystal becomes turbid (right side of the figure below), the light cannot be focused, resulting in blurred vision, or even completely invisible in serious cases.
About 20% of cataracts are caused by excessive ultraviolet radiation.
Here's what cataracts look like:
Macular degeneration
UVA is more penetrating and can reach the retina of the eye, causing damage. Macula is a place where light sensitive nerves gather to help transmit images seen by the eyes to the brain. As you age, there are some degenerative changes in the macula (right side of the image below), such as deformation and bleeding, which can be accelerated by excessive UV light.
Skin cancer
Excessive UV exposure also increases the risk of skin cancer, especially UVB.
Therefore, sunglasses are not only fashionable, but also necessary for eye health.
The first factors to consider when choosing sunglasses are:
How to protect our eyes as much as possible?
The ability to block ultraviolet light
Sunglasses with high shielding UVA and UVB are preferred
Although sunglasses, to some extent, can protect against ultraviolet rays, but to choose sunglasses that can shield most UVA and UVB ultraviolet rays, shield at least 99% UVB and UVA.
Be sure to look carefully at the UV shielding on the label. Those who don't indicate UV protection should not buy Sunglasses from reliable stores. Besides, a wide brimmed hat is a good choice
The color of lenses is exquisite
The color of the lens itself has nothing to do with its ability to protect against ultraviolet rays, not that the darker the lens, the better. However, the color of the lens will affect the contrast between the color we see and the background color. So, in different situations, for different people, the choice is not the same.
Gray lenses reduce light intensity and do not affect contrast or distorted color. Brown lenses block some blue light, enhance contrast, suitable for snow sports, also suitable for bright light and open background. Amber / yellow lenses enhance contrast, because they block most or all of the blue light, so they are popular in hunting. Hunters can easily see their targets in the sky, and they are good for snow sports. However, they are bad for any situation that requires color recognition, such as driving a car.
Patients with macular degeneration or diabetic retinopathy may consider amber or brown lenses. These colors enhance contrast and help patients see better.
Red / orange lenses are suitable for snow sports, but only for cloudy days. Violet lenses are suitable for clay targets on a green background. Bronze Sunglasses are more suitable for golf. Blue and green sunglasses are more suitable for tennis.
Do you want a polarizer?
First of all, polarizers and UV protection are totally different things. Although many sunglasses are polarized lenses, the polarizers themselves cannot shield the ultraviolet rays.
In short, all kinds of objects in nature will reflect sunlight. The working principle of polarizer is to reduce the direct light to the eyes from all angles by applying special chemicals on the lenses.
Advantages of polarized lenses include:
Clearer field of vision, especially when the light is bright, enhance contrast and reduce color distortion, reduce glare and reflection, and reduce eye fatigue
These advantages make polarized lenses very suitable for sunglasses, especially in outdoor activities.
Here's a comparison: no polarizer (left) and polarizer (right). Polarizer reduces glare caused by reflection from water surface and increases contrast.
Polarizing lenses also have some disadvantages and are not suitable for the following situations:
Look at the LCD screen. It is difficult to see LCD screen with polarizer. If you need to look at the instrument cluster or screen, the polarizer is not the best choice. Flying in low light or at night
How to know if your sunglasses are polarizers?
Just try. Choose a reflective plane, the polarizer will reduce the glare caused by the plane reflected light, increase the contrast, and see more clearly. Then, look at the LCD screen. The polarizer will make the screen dark and hard to see.
Face shape and sunglasses
Finally, we can talk about fashion. Let's take a look at some sunglasses. Various styles and styles are shown in the figure below.
Then, choose the right shape for your sunglasses based on your face shape. The following are recommended sunglasses for different face types:
Oval face: it can be called "perfect face shape" and can wear glasses of any style. Just avoid the frame being too thick or too thin.
Square face: this type of face has obvious edges and contours. You can choose round glasses to balance it and make sure the frame is not too thick. Try to choose wide sunglasses and avoid using rectangular glasses.
Round face: full cheeks, round chin. Choose a polygon or square Sunglasses with angle design to balance a little. Thicker frames can also be harnessed.
Long face: choose large lenses and polygonal frame to decorate. Consider the popular retro glasses and sports glasses.
Flat face: choose a darker lens and frame to highlight the face contour. Bright colors can also make expressions more vivid!
No matter which one you choose, make sure the sunglasses are suitable and comfortable to wear.
Make sure that the sides of the head are not pinched. The weight of the glasses should be evenly distributed between the ears and nose. Your eyelashes should not touch the frame or lenses. The glasses should be right on the bridge of the nose and the ears, without leaning to one side.
Driving Sunglasses
As we grow older, our pupils grow larger and more sensitive to light. Direct sunlight is often too harsh. In order to see better when driving, try to choose polarized lenses, which are most suitable for reducing glare. This is particularly important if you have had an operation, such as LASIK.
In addition, choose brown, gray, or yellow lenses to reduce color distortion.
Do children need sunglasses?
UVA and UVB radiation damage is cumulative over the course of a lifetime, the U.S. vision Commission warned, so let children know the importance of wearing sunglasses as early as possible. If you are outdoors for a long time, the six-month-old child will start to protect his eyes.
Prescription glasses
Prescription glasses, especially those with polycarbonate lenses, often have some built-in UV protection. Lenses that automatically darken when outdoors usually prevent UV and glare. In addition, optometrists can help us choose the right sunglasses.
Conclusion
It's important to protect your eyes. Sunglasses are essential. The first choice is to shield 99% of UVA and UVB functions, followed by color and style. Polarizers are a good choice for outdoor activities and driving. Children need it, too.
Choose a cool sunglasses, anti UV plus polarized light, enjoy the sun!
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