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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Lens is a disposable product, once processed and made, can not modified, to avoid the loss can made, should be  consider the correct choice.

Select lens essentials: according to their work, life needs,choose the performance of glasses should have, in the choice of glasses corrected vision, use distance, and glasses degree, but also should consider the different performance characteristics of different lenses.

1. Lens color

People who have high visual requirements for vision, color, and distance, such as students, car drivers, surgeons, and artists, should choose clear and colorless lenses. If the driver puts on the lens with heavy color, he is not sensitive to the change of distance and does not judge the distance accurately, which is easy to cause accidents.

2. The shape of the lens

The shape of the lens depends on the shape of the frame

3. Light transmittance of the lens

Optical lens with multilayer anti-reflection film, colorless optical lens and aspheric surface ultra-thin optical lens have better transmittance.

4. Thickness of lens

It is related to the size of lens diopter, the refractive index of lens, the size and shape of lens frame, the distance between pupil and light center, the axial position of astigmatism, and the properties of lens (concave and convex).

5. The weight of the lens

Related to lens materials, glass lenses are heavier than resin lenses. The same lens material is heavier than the major one and weighs less than the specific gravity, and the larger one weighs less than the volume (depending on the lens strength and shape).

6. Hardness of the lens

Glass lens than resin lens hardness is high, more wear - resistant.

7. Lens strength

Resin lens than glass lens strength, impact resistance is not easy to break.

8. Special functions of lenses

Such as anti - ultraviolet, anti - electromagnetic radiation, anti - infrared, high temperature, oil, acid and alkali resistance, anti - dispersion, anti - deformation (ultra-thin aspheric lens), anti - glare and other functions. Such as electric, gas welding lenses, computer lenses, underwater lenses, fishing lenses are different.

The above key points are very important for choosing a good lens. Do you remember them clearly?

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As for optometry, some people don't pay attention to it. Some people have some misunderstandings. Today, I'd like to talk about some common sense of optometry, and I hope you can treat it scientifically and correctly.

1, glasses fitting, generally follow the principle of the best vision maximum positive mirror.

Maximum positive :

To myopic patient points to can achieve optimal eyesight namely (1.0) when the lowest myopia degree is number, when ensuring the eye sees far already so clear and bright, see close again won't overfatigue. For patients with hyperopia, it is the highest degree of hyperopia at the time of optimal vision (1.0).

To myopic patient points to can achieve optimal eyesight namely (1.0) when the lowest myopia degree is number, when ensuring the eye sees far already so clear and bright, see close again won't overfatigue.

For patients with hyperopia, it is the highest degree of hyperopia at the time of optimal vision (1.0).

2, corrected visual acuity refers to monocular corrected visual acuity, monocular corrected visual acuity has reached 1.0, binocular corrected visual acuity may be 1.2, sometimes do not need to often use the eye patients to correct visual acuity to 0.8.

3, there is a principle when matching glasses: myopia mirror rather than shallow, not deep, correct to 0.9 to 1.0 is appropriate; Farsightedness mirror should "give enough", it is how many degrees match how many degrees.

4, glasses is not corrected the higher the better, some myopia patients hope to get glasses to correct the vision of 1.5, that the higher the better, in fact, will damage the eye's regulatory function, causing visual fatigue.

5, some patients hope to correct visual acuity does not reach 1.0, afraid to see the more clearly the increase in myopic degree faster, this is also a misunderstanding, long-term will deepen the degree of myopia

7. Myopia can reach 1.0 or above through lens correction. If it does not reach 1.0 or above, there may be several problems:

Glasses are not well matched there is myopic amblyopia there is myopic fundus change there are myopia complications

The glasses don't match

Have myopic amblyopia

There are myopic fundus changes

There are nearsightedness complications

8, choose to go to a regular eye hospital with optometry glasses is very necessary.

Doctor reminds: optometry adds lens to want to choose normal hospital, minor degree grows fast, want to see a doctor in time, adult a pair of eyes is most multifunctional two years should be replaced in time.

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The whole process of buying a pair of glasses includes

1. Detect the accurate luminosity of eyes and find potential problems

2. Recommend suitable products with prescription

3. Processing and manufacturing

IV. after sales

Possible risks of online shopping

Is the product a qualified optical product

Whether the processing is qualified or not is suitable for the thing you choose.

If it's all right, congratulations on saving money

Why is it cheap? Because online is just a part of buying products. The other link is to take the ride of physical stores.

In order to promote the effect of free optometry free frame or lens free processing free, all the values are reflected in a product. Then compare this product with the Internet, it's really profitable.

So can these really be free? Obviously not, but the core value of glasses is these free. The product itself is not so valuable. The professional services and shopping experience you enjoy in the physical store are valuable.

If you sell glasses as a regular product in the future, how much more money and time will it take you to enjoy these free products now. (you can find out how much optometry charges in some developed countries and how long the period of lens taking is)!

Of course, everyone wants to save money. If you know your accuracy, and the degree has been stable, and the quality requirements are not high, you can choose a shop with high evaluation to buy online.

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