How to judge the quality of a pair of glasses?

1.  
2. Only by understanding the parameters of the glasses can one judge the quality of the glasses.  
   Let’s start with how to choose lenses. We will discuss several aspects, including refractive index, abrasion resistance, choice of spherical lenses, Abbe number, anti-fouling ability, brand selection, and functional selection.

1. 1.Refractive Index

   The refractive index of a lens is determined by the material used to make the lens.
   With the same center thickness, lenses made from the same material and prescription will have thinner edges as the refractive index increases. When comparing the same brand, the refractive index indicates the difference in materials used, which also helps determine the price of the lenses. The higher the refractive index, the higher the price, and vice versa.

Refractive Index Selection Reference:
(For reference only, do not strictly follow)

• 1.56: 0 — 400° (-4.00D)
• 1.60: 300° (-3.00D) — 600° (-6.00D)
• 1.67: 400° (-4.00D) — 800° (-8.00D)
• 1.74: 800° (-8.00D) and above

2. 2.Abrasion Resistance

   The reason we mention abrasion resistance is that when resin lenses first entered the market, they were not very abrasion-resistant, and after about six months of use, the lenses would get scratched. However, with continuous technological advancements, the surface hardness of regular resin lenses has increased. Initially, the surface hardness of regular resin lenses was around 2-3H, but after hardening treatments, it reached 4-5H. Nowadays, resin lenses can achieve a hardness of 6-7H, and with the addition of surface anti-scratch coatings, the issue of lens wear resistance has been largely addressed.

Although the hardness still cannot compare to that of glass lenses, most glass lenses have already been phased out of the market, and the remaining glass lenses are primarily used for high refractive indices, such as 1.8 or 1.9.

Let’s also mention PC lenses.
PC lenses are light, have high impact resistance, and are not easy to break, which are their notable advantages. However, the maturity of domestic PC lens brands still needs to be confirmed, so it’s recommended to choose lenses from well-established brands.

A little tip for you—To check the hardness of a lens, you can use an object made of the same material to draw circles on the lens surface. By examining the depth and thickness of the scratches, you can roughly determine the surface hardness of the lens.

3. 3.Spherical vs Aspherical Lenses

   A spherical lens is a lens that is cut from a spherical surface, resulting in either a convex or concave shape.
   However, spherical lenses inevitably cause optical distortions, particularly issues like astigmatism and barrel distortion, among others. To correct these drawbacks, aspherical lenses were developed (usually referring to single-sided aspherical lenses).
4. An aspherical lens refers to a lens with a rotational surface that has the same non-circular cross-section along all meridians, such as a parabolic shape.

The main advantage of aspherical lenses is that they eliminate image distortion at the edges of the lens. The edges of these lenses are also approximately 1/3 thinner than those of standard spherical lenses. As a result, aspherical lenses are typically more expensive.

Additionally, double-sided aspherical lenses have appeared on the market. These lenses provide clearer vision across the entire field of view and offer better image quality, but of course, they come with a higher price tag.

4. 4.Abbe Number

   The Abbe number is the dispersion coefficient, and it is an important indicator for measuring the clarity of lens imaging. It is typically expressed as the reciprocal of the dispersion coefficient, also known as the Abbe number.

The higher the Abbe number, the lower the dispersion, meaning the image quality will be clearer. Conversely, the lower the Abbe number, the higher the dispersion, leading to poorer image clarity. The Abbe number of a lens is related to its refractive index: the higher the refractive index of the material, the greater the dispersion, meaning the Abbe number will be lower.

Thus, in terms of this single metric, a lower refractive index is better for minimizing dispersion. However, when selecting lenses, it’s important to consider your overall vision needs. The most important factor is choosing lenses that are suitable for your specific vision, rather than focusing solely on the Abbe number.

5. 5.Anti-Fouling Ability

   In recent years, many lens brands have shifted their research and development focus from increasing hardness and light transmittance to enhancing the smoothness of lenses in order to improve their water and oil resistance.

One of the most representative lenses in this category is the Zeiss Lotus Coating Series.

（Testing Method:You can test the anti-water performance by cleaning the lens and dropping a single drop of water onto the surface. Move the drop around the lens. If the water forms one bead and stays together, it indicates good water resistance. If the water spreads and disperses across the surface, it means the lens has a weaker anti-water function.）

7.Choosing the Right Brand

Essilor (France) – A well-established, big brand known for its stable quality, abrasion resistance, ease of cleaning, and strong anti-fouling properties. It currently holds the highest market share in the lens industry.

Nikon (Japan) – Focused on image quality with reliable technology, but its market share in China is not very high. In particular, photochromic lenses and custom lenses require processing in overseas factories, leading to long customization cycles.

Hoya (Japan) – Another Japanese brand, Hoya has a relatively high market share in China, especially in the blue light blocking lens sector. It is the first brand in the world to promote blue light lenses, with prices being moderate.

Rodenstock (Germany) – Known for military-grade quality, precise grinding, and high coating strength, Rodenstock lenses are very expensive. They have always focused on the eyewear industry, so their reputation is mainly limited to the professional field, and not many people are familiar with the brand.

The technology required for lens production is highly advanced. In comparison, large brand lens companies have far more robust technological capabilities and research and development accumulations. Companies like Zeiss and Essilor have been established for many years, while most domestic lens processing companies lack sufficient technical foundation, and their quality control systems still need improvement.

However, there are also some good brands worth mentioning, such as Wanxin and Mingyue.

Many people are also concerned about how to identify genuine lenses.

Lens production and processing technology is extremely precise. Without professional testing instruments provided by the lens manufacturer, it is impossible to definitively determine whether a lens is genuine. As a consumer, you can only rely on anti-counterfeit labels, the original packaging, and verification codes to verify authenticity. Some large brand lenses (such as Essilor) also have a brand-specific fogging mark that appears when you breathe on the lens.

However, it should be noted that, theoretically, all of these anti-counterfeit measures can be faked.

Because of the high threshold for authenticating lenses, many eyewear shops might sell counterfeit products. In this case, the best way to avoid encountering fake lenses is to get recommendations from friends or rely on online reviews. Finding a trustworthy, reliable retailer is the most practical solution.

Now that we’ve discussed lenses, let’s take a look at how to choose the right frame.

First, let me make one thing clear: when it comes to which frame suits which face shape, I have only one answer for you:
Look in the mirror, look in the mirror, look in the mirror.

All reference manuals are just LESE—you can refer to them, but don't take them too seriously.

So, let's talk about the two issues of wearing comfort and frame quality identification.

A good frame should be made from safe, reliable, and skin-friendly materials, and it should be lightweight, durable, and resistant to deformation when worn on the face. Additionally, from the perspective of the wearer, the frame should be chosen based on its practicality.

• Choosing a frame based on vision needs and purpose: If the glasses are intended for long-term wear, you can choose a lighter frame to reduce wear fatigue, even if other conditions are relaxed.
• If the glasses are only worn for focused activities like reading or using a computer, you can select a frame based entirely on personal preference.
• People with high myopia should avoid choosing semi-rimless or rimless frames, as the thicker lenses may not look aesthetic and can be more prone to damage when paired with these types of frames.
• Those with high astigmatism should avoid rimless frames, as the lenses paired with such frames can cause astigmatic axis displacement after extended use, leading to image distortion.
• Special needs: If the main purpose of the glasses is to enhance appearance or match a particular occasion, and there are no significant restrictions based on vision, you can select a frame based on your specific needs.

What makes a good frame?

You can basically determine the quality of a frame by looking at three details:

1. 1. Color Quality – Check for consistency.
   Place the glasses flat in front of you, and under the same lighting conditions, observe if there is any difference in the color depth of the temple arms. Sometimes due to manufacturing errors, the left and right temple arms may have asymmetrical coloring.

2.  

3. 2. Craftsmanship – Pay attention to the details.
   Craftsmanship is the guarantee of the frame’s quality, and the excellence of a frame's craftsmanship is often reflected in its details.

   • (1) Are the temple arms flat?
     Place the frame flat on a table and check if the contact points are even. If one side is higher than the other, you should ask a professional to adjust the temple arms to achieve balance and symmetry.
   • (2) Inspect the welding points of metal frames for cracks.
     Welding changes the material's stress structure due to heat effects, and poor welding or material fatigue can cause the frame to break under pressure.
   • (3) Check the symmetry and security of the nose pads.
     Ensure both sides are symmetrical and that the nose pads are securely fixed.
   • (4) Test the flexibility of the temple arms.
     Many believe that the tighter the temple arms, the better, but this is a misconception. If too tight, it may indicate insufficient lubrication of the screws, which can cause damage to the arms. Conversely, if too loose, it may mean the screws are not properly tightened. The ideal fit should be a moderate tightness.
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   • 3. 3.  Markings – Check the Material
        Many frames indicate the material used on the temple arms, especially for frames made of precious metals such as gold and titanium. Let's briefly look at these markings:

     • (1) GF/GP:

       • GF stands for gold-plated frame, which means a thin layer of gold is fused onto another metal base to create the frame.
       • GP stands for gold-coated frame, which means gold is electroplated onto the surface of a frame made from another metal.

     • (2) Ti-P/Ti-C:
       Ti indicates the presence of titanium material.

       • Ti-P refers to pure titanium.

       • Ti-C refers to titanium alloy, and so on. Let’s also discuss the differences between pure titanium, titanium alloy, β-titanium, and memory alloy:

       • A. Pure Titanium
         Pure titanium is defined as titanium with a purity of over 99%. Frames made from pure titanium have excellent properties, including a high melting point, light weight, strong corrosion resistance, and a durable electroplated surface. This guarantees both the aesthetic appeal and durability of the frame.

       • B. β-Titanium
         β-Titanium can be understood as a different molecular form of titanium. While its purity is not comparable to pure titanium, its strength, fatigue resistance, and environmental corrosion resistance surpass that of pure titanium.

       • C. Titanium Alloy
         The definition of titanium alloy is quite broad, as any material containing titanium can be considered a titanium alloy. Therefore, the quality and grade of titanium alloy frames can vary greatly. The composition of the titanium alloy directly influences the price of the frame. Using titanium alloy for frames is not necessarily a cost-saving measure but is intended to enhance the material’s application performance.

       • D. Shape Memory Alloy
         Composed of metals such as nickel, titanium, and vanadium, shape memory alloys have excellent elasticity. The temple arms can bend to a greater degree than β-titanium but will return to their original shape when released. This unique property is why it is called a "shape memory alloy."
         The price differences between titanium materials are not just due to cost but also because each has unique craftsmanship and product performance characteristics. Thus, a frame made of a certain material doesn't necessarily mean it will be priced higher.

     In recent years, TR material has become especially popular. TR90 is a memory polymer material that is lightweight, about half the weight of acetate frames, reducing the pressure on the nose and ears, making it more comfortable to wear. It comes in vibrant colors, more vivid than standard plastic frames.

     • Impact Resistance: Effectively prevents eye injuries caused by impacts during sports.
     • High-Temperature Resistance: Can withstand temperatures above 300°C for short periods, is not easily melted or burned, and does not deform or discolor, making the frame more durable.

     TR100 is an upgraded version of TR90, which has memory features.
     It is lightweight and can float on water, reducing the weight on the nose and ears. It has elasticity; when bent or stretched and then released, it quickly returns to its original shape without deforming or breaking. The frame comes in vibrant colors and has a stylish appearance, combining the weight of acetate with the feel of metal.