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What is a progressive lens?

Progressive multifocal lenses are lenses with different upper and lower powers for seeing far above and below for seeing near. The distance from the fixed far power above the lens to the near power fixed below the lens does not change suddenly, but a gradual transition between the two through the gradual change in refractive power. Compared with ordinary lenses, there are many advantages. The appearance of the lens is like a single vision lens, and the dividing line of the power change is not visible. Not only is the appearance beautiful, but more importantly, it protects the age privacy of the wearer, and there is no need to worry about revealing the age secret due to wearing glasses.

Since the change of the lens power is gradual, there will be no image jump. It is comfortable to wear and easy to adapt. So it is easy to be accepted. Because the degree is gradual, the replacement of the adjustment effect is gradually increased according to the shortening of the short distance. There is no adjustment fluctuation, and it is not easy to cause visual fatigue. Clear vision can be obtained at all distances in the visual range.

Such a pair of glasses meets the use of long-distance, near-use and various distances in the middle at the same time. It is especially good news for teachers, doctors, music workers, and computer operators, because these people not only need to see far and near objects clearly, but most of the time they also need to be able to see middle distance objects such as blackboards, piano scores, and computer screens. . This is not possible with any lens other than progressive lenses.

Study On the Night Driving Glasses

Researchers at Harvard's Schepens Eye Research Institute recently conducted a study to find out if wearing night driving glasses while driving at night is good for vision. All 22 participants drove under four conditions that simulated night driving, wearing either yellow night driving glasses or glasses with clear lenses. Each participant drove with or without the headlight glare simulator activated to simulate the effect of oncoming traffic. The study found that wearing glasses while driving at night didn't seem to improve: how well the participants were able to recognize pedestrians at night and negative effects of headlight glare on pedestrian detection. Our data suggest that wearing yellow lenses while driving at night does not improve performance at the most critical task: pedestrian detection, the study's authors said. A small 2019 study showed that night driving glasses can actually slow down visual reflection by a fraction of a second, making night vision worse.

How do drivers wear glasses or sunglasses better?

We should pay attention to the dim light at night on the impact of vision, At night, for the people who wear glasses, it is best not to drive, but to prevent fatigued driving. If you need to drive, you must choose clear and appropriate optical glasses. When the light is strong in the field, it is advocated to wear light-colored sunglasses with appropriate degrees to ensure driving safety. When wearing glasses to drive, for the observation of road conditions, we should focus on the use of the head movement. Do not use eyes to move, to prevent the effect of the prism, especially the patient with high myopia should pay special attention. Shaded sunglasses, coated with reflective material, block out light from above and increase horizontal and lower light, which makes it easier to see the platform. Clip-on sunglasses are suitable for people who wear glasses themselves. You can go straight with a pair of myopic sunglasses for a higher price.

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.

Competition in visual marketing

The offline experience of consumers is pretty important. Store space design, planning and layout, and commodity display form are important parts of visual marketing. If all three can be balanced and matched, it will drive sales growth.

The design evolution of progressive lenses

Spherical and aspheric designs

The design of the front surface of the far-use area of the early progressive lens is similar to that of the ordinary spherical single vision lenses, so it is called a spherical progressive lens. Since 1974, the front surface of the far-use region of the lens is designed to be aspheric by designers, which not only reduces the peripheral aberration but makes the lens thinner, lighter, and less powerful.

Hard and soft design

For hard design, the channel is short, and the gradient is large. The near-use area position is high. The effective visual area of remote and near-use areas was larger. Peripheral astigmatism is relatively concentrated. Because surrounding astigmatism increases rapidly and the distribution is dense, the curve effect is more obvious. The gradient area is narrow. It is more difficult and takes longer for wearers to adapt.

Lenses with soft designs have slower gradients, longer gradients, and wider gradients. The angle of rotation of the eye from the far area to the near area is greater. It's easier to get used to. Compared with the hard design, the effective visual area of the far and near use areas is smaller, and the location of the near use area is lower.

Single, diverse, and individualized design

Initially, the progressive lenses used a single design, in which each basic curve was scaled equally and a luminosity combination was added within the range of its semi-finished lens blanks. The steepest base curve uses the same lens design as the flattest base curve. Lenses designers quickly realized that the overall performance of the lens could be improved by microcustomizing the lens design, leading to progressive lenses with multiple designs. This kind of design is called diverse design. By the mid-1990s, there was the emergence of individualized lens designs. In addition to using different gradients, these first individualized lens designs used steeper baseline curves with a slightly larger approach area to compensate for increased magnification and reduced field of view.

Symmetrical and asymmetric design

There is no difference between the left and right eyes in the symmetrical design of progressive lenses. As the eyes turn inward when they see near objects, the gradual gradient area gradually tilts to the nasal side from top to bottom, so the left/right progressive lenses should be rotated clockwise/counterclockwise respectively during processing. An asymptotic lens with left and right eye divisions is called an asymmetric design. The gradient is gradually and moderately inclined to the nasal side from top to bottom. The refractive force, astigmatism, and vertical prism of the two sides of the left and right gradient of the asymmetric design lenses are basically similar. At the same time, considering the characteristics of eye movement parameters in binocular vision, the peripheral aberrations of the corresponding positions of the left and right lenses were appropriately balanced to improve the visual effect of the wearer.

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Can Pinhole Glasses Improve Your Vision?

The most important question may be whether the pinhole glasses improve your eyesight and some people may have this trouble. Some people say pinhole glasses can improve the vision of nearsightedness or astigmatism. But there is no evidence to prove that.

Although pinhole glasses can improve vision to some extent, they are not practical for everyday use. Pinhole glasses are designed to block part of your direct vision and restrict peripheral vision. They would cut the amount of light entering your eyes so as to reduce the visual quality of an image. Hence, it would be not recommended to wear pinhole glasses in daily life.

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