How to choose the ideal lens?
Source: Leader Vision | Date of issue: 2020-12-08 15:38:29 | Views: 16761
When the degree of myopia increases, the glasses will inevitably change, and a good and appropriate pair of glasses will add points to the external image. When changing glasses, you must try them on, choose your own, and you must buy frames before mat…
1. Choose lens material
Lens materials are mainly divided into glass, resin and PC. Although glass lenses have good optical performance, they are fragile and harmful to eye health. Nowadays, few people are equipped with glass lenses. More and more people choose resin lenses. In terms of performance and health, resin lenses are very good. Resin lenses are more expensive than glass and PC lenses, but resin lenses are also graded, and you can buy them at a price of 100 yuan.
Second, choose the spherical surface of the lens
As people's solutions to the eyes deepen, we find that our eyes are not spherical, so the lens that adapts to this kind of non-spherical eyes is called an aspheric lens. Aspheric lenses can help us get better visual quality. The aspheric lens is lighter and clearer than the equal degree spherical lens, which is suitable for people with high levels.
The design of the aspheric lens makes up for the deficiency (aberration) of the spherical lens design, so that the convex surface of the entire lens has a different radius of curvature. Theoretically speaking, with this design, the lens can get exactly the same visual effect as the front eye. In addition, the curvature of the lens is reduced and the thickness of the lens is reduced, so that the wearer's glasses look closer to reality. The convex or concave surface of the lens is like a part cut from the sphere, called a spherical lens. Convex or concave lenses for myopia or hyperopia have only one radius of curvature. The convex surface of the lens with the inner surface tc for astigmatism has one radius of curvature, and the concave surface has two radii of curvature intersecting perpendicularly.
The surface curvature of the aspheric mirror is an aspheric mirror design, which has the following advantages compared with the spherical mirror design:
1. Clearer: The aspherical lens with unique coating treatment has better visual performance and presents clearer and comfortable visual effects.
2. Simpler: After putting on the aspheric lens, you can hardly feel its existence, lose weight and enjoy the ease it brings to you.
3. More natural: aspheric design is more natural, visual distortion is smaller, and visual objects are more realistic.
Three, choose the refractive index of the lens
The numbers 1.56, 1.61, 1.67, 1.70, 1.74 and other numbers on the lens indicate the refractive index. The higher the refractive index, the thinner the lens of the same power will be matched. Prices will also climb significantly. In addition, the higher the refractive index, the stronger the dispersion, that is, the visual effect will be reduced.
The higher the refractive index of the material, the stronger its ability to refract incident light, and the thinner the lens. That is, the center of the lens has the same thickness, the same power and the same material, and the edge of the lens with high refractive index is thinner than that with low refractive index. The thinner the lens, the lighter the weight and the higher the price.
Four, pay attention to the pupil distance
When we wear glasses, we need another data. That is the pupil distance. Interpupillary distance is the distance between the center of the pupils of the eyes when we look straight ahead. The principle of wearing glasses is that the exact center of all lenses must correspond to the exact center of our pupils, and the deviation degree is wrong. After knowing the pupil distance, the optician can use the machine to grind the lens.
If the interpupillary distance is wide, you can choose a wide nose bridge, try to make the thin point of your lens correspond to the center of the frame, so that the periphery of the polished glasses looks thin.
To sum up, everyone must be responsible for their eyes when wearing glasses. It is a good choice to choose a large chain optical shop for glasses, or go to the hospital for optometry, and then go to some well-known professional online glasses platform for glasses.
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