Type of eyeglasses cloth
There are many kinds of cloth for glasses. There is mainly sheepskin eyewear cloth, and there is microfiber eyewear cloth. There are suede and double-sided cloth and so on. Professional eyewear cloth must use more than 200 grams of weight/per cubic centimeter of microfiber. This kind of raw material chemical fiber is fine, and tactility is soft, so it will not damage the lens. This kind of wipe cloth can be used on a computer screen. The two sides of the cloth are different, and the smooth side is used to scrub the lenses. Because the dirt on the lens is mostly small. The rough side is designed to give you more friction when you touch it with your finger, so you can use it more easily, and you can clean it more.
The lenses of prescription glasses
Common materials for lenses include glass, resin, and PC. The glass is fragile and heavy, and few people wear it anymore. PC film is tough and not fragile, but it is not resistant to high temperature and the surface is easily scratched. The most common type of lens on the market today is the resin lens, which is light in weight, hard to break, and reasonable in price. At present, it is generally recommended that you choose resin sheets, and it is recommended that people with ultra-high myopia choose glass sheets.
Generally, lenses can be divided into spherical and aspherical surfaces according to different curvature designs. When choosing, refer to the degree of the eye. For people with lower degrees, There are fewer differences between the two shapes. For people with moderate to high myopia, aspherical lenses will have better imaging effects and clearer vision.
When choosing a lens, a parameter that is often mentioned is the refractive index. Common refractive indexes are 1.56, 1.60, 1.67, and 1.74. With the same degree, the higher the refractive index, the thinner the lens.
What are the origins of saddle bridge glasses?
Rimless glasses were introduced in 1880 and were popular until the 1950s. Rimless glasses made in 1880 and 1920 lacked a nose pad. Instead, they use a saddle bridge, so they were sometimes called saddle bridge glasses. Horses are the main means of transportation. Early rimless saddle glasses were designed to be close to the face. Rimless glasses with nose pads were introduced in 1921. The nose pad keeps the glasses farther away from the face. In addition, frames can be made much larger.
Parameters of lens material selection
Abbe number
Since the refractive index of the lens material varies for the light of different wavelengths, and white light is made up of various colors of light of different wavelengths, the dispersion phenomenon occurs when the lens refracts white light. The dispersion coefficient is an important index to identify the sharpness of lens imaging, which is usually indicated by Abbe number (Abbe number = dispersion coefficient). The larger the Abbe number, the smaller the dispersion, and vice versa, the smaller the Abbe number, the larger the dispersion, and the worse the resolution of the image.
Impact resistance
Humans have been using glass lenses for about 300 years, and it was not until 1947 that the first resin lenses made of CR39 were produced. A big reason for using resin lenses is their safety, i.e. impact resistance. Only lenses that pass the Drop Ball Test are considered safe. Combining the above two parameters, we can compare different lenses.
Transition Lenses Problems
Here, we will show you some common transition lenses problems.
Transition lenses are typically embedded with photo-sensitive chemicals or coated with similar films that produce the shading effect when exposed to light. This process makes the lens more expensive to manufacture and focuses on prescription glasses, thus raising the transition glasses cost. The transition lenses cost may be twice of the regular glasses lenses.
When you are driving with the transition glasses, they will fail to work. Car windshields typically come standard with anti-glare effects or films and laminates that break up some of the direct sunlight that enters the vehicle. This will reduce the transition lens effects, causing them to register a non-lit condition when the direct sunlight can actually be very bright.
The Advantages of Polycarbonate Glasses
In fact, polycarbonate glasses come with several benefits and this section will show some of them.
First, polycarbonate glasses are safe and are virtually unbreakable. A study found that polycarbonate glasses were more impact-resistance than glasses or other types of plastic lenses.
Second, polycarbonate glasses are thinner than other types of lenses. This feature makes them ideal for people who have strong prescriptions. Lighter and thinner eyeglasses are less likely to slip off your nose and are more comfortable for everyday wear.
Third, extended exposure to UV radiation from the sun can cause damage to your eyes and lead to some eye conditions such as cataracts or macular degeneration. Of course, polycarbonate glasses can block out harmful UV rays from the sun and provide good protection for your eyes.
However, there are some negative voices of polycarbonate lenses.
Bifocal vs Varifocal Glasses: What Are Their Differences?
The above part has introduced some basic information about bifocal glasses and varifocal glasses. So, what are their differences?
- Bifocal glasses have two different prescriptions in one lens, while varifocal glasses have three different prescriptions in one lens.
- There is a distinct line between different prescriptions in bifocal glasses. Varifocal glasses allow getting through other prescriptions smoothly.
- Varifocals can give you a vision at any distance.
- Bifocal glasses are more cost-effective than varifocal glasses.
However, they also have some similarities. Both glasses can be used to correct presbyopia vision. So, when you choose glasses, you can decide to choose bifocal glasses or varifocal glasses based on your needs. If you want to get a pair of corrective glasses online, Koalaeye Optical is recommended. It is an online glasses store and provides all kinds of eyeglasses, sunglasses and frames. In addition, these glasses are stylish and come at a cheap price.
