Comprehensive Knowledge of Glasses Manufacturing and Glasses [Part 4]

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About glasses lenses. 

After talking about the frames, it's time to talk about glasses lenses. Lenses are the most important part of the frames, and can be said to be the soul of glasses. Why say soul, because lenses are functional. Imagine if the frames were not invented, would you still have a pair of glasses if you used a pair of lenses with a rubber band and a stick? Lenses are important, I won't say much, and if you don't even understand the importance of lenses, it's useless to say more.

Main materials and characteristics of lenses.

1. Resin lenses. Lightweight (density about 1.32), impact-resistant, and affordable. The disadvantages are easy to scratch (need coating), low refractive index (1.50-1.74), suitable for ordinary degrees and daily wearers.

2. Glass lenses, high light transmittance (99%), high refractive index (up to 1.9), disadvantages are relatively heavy (density 2.54), fragile, poor safety, suitable for ultra-high degrees (need ultra-thin) and those who pursue clarity.

3. PC lenses, super impact resistance (space suit material), extremely light, the disadvantage is low Abbe number (obvious dispersion), easy to scratch, suitable for children and sports enthusiasts;

4. Tritan lenses, environmentally friendly, high temperature resistant, chemical corrosion resistant, the disadvantage is low popularity, high price, suitable for people who are sensitive to materials (such as allergic constitution).

 

Functional classification of lenses.

1. Basic functional lenses. There are mainly single vision lenses and progressive multifocal lenses. Single vision lenses are conventional corrections of myopia/hyperopia/astigmatism, suitable for people without special needs, while progressive multifocals can correct far, medium and near vision at the same time, commonly used by middle-aged and elderly people, usually used on reading glasses.

2. Protective lenses. Protective lenses include anti-blue light lenses, photochromic lenses, polarized lenses, etc. Anti-blue light lenses can filter harmful blue light from electronic screens and are suitable for use in front of computers. Photochromic lenses have the function of photosensitive color change, transparent indoors and sunglasses outdoors, suitable for people who frequently switch scenes. Polarized lenses can eliminate reflections from water and snow, and are the first choice for drivers and fishing enthusiasts.

 

Key points for lens parameter selection.

1. Refractive index. The higher the refractive index, the thinner the lens (e.g. 1.74 is about 30% thinner than 1.50), but the lower the Abbe number (dispersion coefficient), the lower the visual clarity. Reference selection: low degree (≤300 degrees): 1.50/1.56; medium degree (300-600 degrees): 1.60/1.67; high degree (≥600 degrees): 1.71/1.74;

2. Coating technology. Basic coatings mainly include anti-reflection, waterproof, and anti-oil. Upgraded functions generally include anti-static, reduced dust adsorption, enhanced wear resistance, and less prone to scratches during normal use.

3. Abbe number, that is, dispersion coefficient. The higher the value, the clearer the image (the Abbe number of resin lenses is about 30-40, and the glass lens can reach 55). It is recommended to balance the refractive index and Abbe 

 

number to avoid excessive pursuit of ultra-thinness leading to a decrease in visual quality.

Precautions for the use and maintenance of lenses.

1. Cleaning: After rinsing with clean water, wipe with a special lens cloth in the same direction to avoid scratching the coating.

2. Storage: Avoid high temperatures, such as car dashboards, especially sunglasses, where lenses are easily damaged at high temperatures. They should not be stored in a humid environment and should be placed in a lens box when not worn.

3. Lifespan: Most of the myopia lenses now use resin lenses. Resin lenses are recommended to be replaced every 2-3 years. If there are obvious scratches or the film layer falls off, they should be replaced in time, otherwise it will affect vision and even make myopia worse.

 

About Lens brand

There are many brands of lenses, both imported and domestic. Imported lenses include Zeiss, Essilor, etc. Their prices are relatively expensive, generally more than 500 or even 1,000 yuan. Domestic lenses mainly include Mingyue, Wanxin, and Hoya, etc. These brands of lenses are more economical and affordable. With the continuous improvement of lens technology, the quality is also very good now. So consumers only need to buy according to their needs and budget

 

How to judge the quality of lenses.

How to judge the quality of lenses? For ordinary consumers, it is difficult to judge the quality from a professional perspective. When consumers wear glasses, many people do not even look at the packaging, product name, date, etc. of the lenses, because they are all processed. It is recommended that you take a good look at the next time you wear glasses. It is best to check on the Internet to see the brand, where it is produced, whether it is anti-counterfeiting, etc. Although you say it is useless, it is also a bit of supervision to learn more, especially to let the store keep the packaging and anti-counterfeiting for you. If you wear a pair of glasses for 2 years, you don’t know where the lenses are produced, what the refractive index is, and what you know, but you only know how much you spent. This is a bit ridiculous! For an ordinary consumer, you can look at it from the following aspects:

1. Look at the surface: Check whether the surface is smooth and has no pitting. If conditions permit, you can use a simple magnifying glass to observe. High-quality lenses have a very smooth surface.

2. Look at the overall packaging: Let him show you the overall packaging of the lenses and feel it. Regular brands will have a relatively complete packaging.

3. Check the anti-counterfeiting mark: The anti-counterfeiting mark does not necessarily mean that it is a good thing, but take a look and grasp it.

4. Check the hardness: The surface of high-quality lenses should be relatively hard, and generally a strengthening layer will be added to make it less likely to be scratched or scratched during normal use.

5. Check the additional functions: Especially coated lenses, including coated sun lenses and myopia lenses with reflective films. You can refer to the above judgment of the waterproof and oil-proof functions of lenses.

 

Maintenance and care of lenses

1. The key to the use effect and life of lenses lies in maintenance and care. If the maintenance is good, ordinary lenses must be replaced every 2 years. If the maintenance is not good, it will affect vision in one year and should be replaced.

2. Cleaning: Pay attention to the cleaning method. It is unrealistic to clean with ultrasound every day, so just wash with water, but pay more attention to wiping. If you pass by a big store and have time, ask them to wash your glasses. They all use ultrasonic cleaning, which is more thorough and basically free.

3. Placement: It is best not to let the lenses touch hard objects. Place them on the side on the table. This principle is understood. If you don't use it for a long time, it is best to wipe it dry with a glasses cloth and store it in a special glasses case. 

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