Evolution of photochromic lenses
Thirty years after Corning invented color-changing glass lenses, another company has carried forward the color-changing glass lenses --Transitions Optical. In 1991, it became the first company to commercially manufacture resin color-changing lenses. Since its inception, the company has been a joint venture between PPG Industries (51%) and Essilor (49%). In April 2014, Essilor acquired a 51% stake in PPG. At present, the mainstream is resin photochromic lenses.
Evolution of hard coating technology
The first generation of the use of hard coating technology began in the early 1970s, the quartz material is deposited on the surface of a resin lens under vacuum conditions, form a very hard anti-wear film. However, due to the mismatch between the thermal expansion coefficient and the film base material, it is easy to delaminate and crack the film. Instead, it forms the mottle on the surface of the lens, and the effect is not optimal.
The second generation of hard coating technology is the use of the 1980s. The surface of the resin sheet is coated with a material with high hardness and not easy to be brittle and cracked by an immersion process. At this time, anti-reflection coating lenses had appeared and gained the recognition of consumers, but the mismatch between adding hard coating and anti-reflection coating still caused serious lens wear.
The third generation of hard coating technology was developed in the 1990s, mainly in order to solve the problem of wear resistance after coating resin lenses with an anti-reflection film. The hardened material evolved into a polymer organic matrix material.
Fourth-generation coating technology is dominated by silicon atoms, in which the hardened solution contains both organic substrates. It contains inorganic ultrafine particles, including silicon elements, which make the hard coating not only tough but also hard.
Magnesium aluminum spectacle frame
One of the characteristics of magnesium-aluminum spectacle frames is that they are resistant to corrosion, sweat and wear. In addition, spectacle frames made of magnesium-aluminum are also rich in color and look very textured, so many business people like to use such spectacle frames to display Its own charm.
How many degrees of myopia do I need to wear glasses?
Students are the most nearsighted because they need to read and study every day. Many people have myopia during their student days. During the physical examination, everyone will check their eyesight first. Generally speaking, if the visual acuity is lower than 0.6, it means that you may be near-sighted to 0 degrees. At this time, you need to go for optometry to see the specific vision situation and see if you need to wear glasses. If the visual acuity tested exceeds 200 degrees, you must wear glasses at this time. If you do not wear glasses, your vision will be greatly affected, and the degree of myopia will rise quickly. For this reason, you must wear glasses in time to correct your vision. If the degree of myopia does not exceed 0 degrees, this is pseudo-myopia and does not require glasses. However, you should always take care to protect your eyes, avoid staring at things at close range for a long time, and don't let your eyes get too tired, so your vision will slowly return to normal.
Problems you may encounter when wearing your glasses.
The glasses are too tight. They clamp to the temple. Glasses slip easily. Too long or too short at the bend, and there are too small contact areas of the nose pad. Glasses are too far from the eye, and the lenses are crooked or asymmetrical. These are some of the problems you may encounter when wearing glasses.
How to buy contact lenses online?
Choose well-known brands.Nowadays, the contact lens brands in the market are mixed, with the proliferation of inferior products, but there are still some authoritative and well-known ones, like Johnson & Johnson, Bausch & Lomb, which are products recognized by most users, and you can rest assured to buy them.
The principle can be followed when choosing glasses for people with round faces
Choosing the right frames is not an easy task. Choose a color closer to your skin or lighter than your eyebrows for a more natural look. In reality, there is no exact answer to choosing glasses based on face shape. The rule to follow when choosing glasses for a round face is to make up for the lack of a round face by choosing an angular style. The vertical lines of the frame should be narrow.
