General Knowledge of Eyeglasses

The easiest way to test your glasses is to look at them sideways into the light, and the aperture will be about 50 degrees. Here is what you need to know about eyeglasses. Contact lenses: There are many brands of contact lenses on the market today, and various brands are divided into different categories according to their performance.

Each type of lens has different characteristics, and the diversity of varieties and functions makes it difficult for consumers to choose, so which one to choose is the most reassuring? First of all, when choosing lenses must pay attention to see if a brand has a registration certificate issued by the State Food and Drug Administration. The State Food and Drug Administration uses ISO international standards to test lenses for various functions, such as the degree of damage to the cornea, the process of grinding the lenses, the materials used and the water content and breathability of the lenses, so the quality of brands with registration certificates is generally guaranteed.

Secondly, the degree of the lens, size, material, use time, etc. are what should be noted. Many people think that the degree of frame glasses and contact lenses are exactly the same, so they tend to buy contact lenses according to the degree of frame glasses.

In fact, this is not right, because for the same eye, there is a difference between the degree of contact lenses and the degree of frame glasses, the higher the degree the more obvious this difference. The difference between the two is generally not much for lenses below 400 degrees, but above 400 degrees, you need to add or subtract degrees.

Contact lenses for myopia correction are lower than frame glasses, for example, if the optometry result is 450 degrees of myopia, the contact lenses need to be reduced by 25 degrees and only 425 degrees can be fitted. For example, if the result is 450 degrees of farsightedness, the contact lenses need to be increased by 25 degrees, and 475 degrees are needed.

The size of the lenses is generally determined by the size of the wearer's black eye part, with larger lenses for larger black eyes and smaller lenses for smaller black eyes. People who are prone to dry eyes should choose contact lenses with lower water content.

People who often work in the sun can choose lenses with UV protection. People who are generally prone to allergies, those who are often exposed to cosmetics, and those who are often in dusty environments are better suited to wear disposable contact lenses.

General eyeglass frames: China has become the country with the highest incidence of myopia in the world. According to statistics, the population suffering from myopia in China has reached more than 300 million, accounting for about one-third of the number of myopia patients in the world, the world ranking has jumped from the fourth place in 1998 to the second place now.

According to statistics, the proportion of Shanghai people with myopia tops the list of major cities in China, with 28% of elementary school students, 38% of middle school students, 58% of high school students, and up to 80% of college students. When you want to get yourself a pair of glasses, the word "fit" is the most appropriate.

Frames. For people who need to wear glasses, the purchase of frames is crucial.

When choosing glasses, consumers should not only consider the shape of the face, the bridge of the nose, the distance between the pupil and the glasses, but also coordinate with the skin tone and hair color, so that they can wear the temperament and poise. Generally speaking, people with wide faces should not use small and narrow frames, and people with long and thin faces should not use wide frames.

For children, it is best to use a plastic frame, to the frame can be attached to the nose surface is appropriate. For some highly myopic and highly farsighted consumers, due to high diopter, should generally choose a small frame, the smaller the lens the better.

Commonly used eyeglass frames are as follows: plastic frames, metal frames, nylon wire frames. Compared to frames, the types of lenses are much less, but its merits are the decisive factor in measuring the quality of a pair of glasses, so consumers must be careful when buying lenses.

Glass lenses: wear-resistant, but relatively speaking, it is heavier than other materials of lenses, but also easy to break. Polymer resin lenses: these lenses are lighter in weight than glass lenses, impact resistant and less prone to breakage, but less hard, so they are prone to linting and scratching.

To measure the quality of a pair of glasses lenses, in addition to the material, to see the refractive index of the lens, the higher the refractive index, the thinner the lens, the higher the price.

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