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.
Adjust the nose pad
The height of the nose pad is adjusted by first holding the glasses with one hand and holding the nose pad with pliers with the other. Then the pliers are lifted up and the nose pad is moved down until the glasses are in the correct position on the face. The asymmetrical adjustment method is to first hold the frame of the eyeglasses with one hand, the other hand clamps the nasal plate with pliers. Then twist it in the direction of the correct tray position so that the surface of the tray is in contact with the two sides of the nose. Wrap one side of the lens of the glasses to be operated with a cloth first to prevent the screwdriver from slipping and scraping the lens during the operation. Don't scratch your glasses by adjusting your nose pad.
Who is suitable to wear progressive lenses
Progressive multifocal glasses are suitable for people with presbyopia or visual fatigue, especially teachers, physicians, musicians, computer operators, etc. They not only need to see far and near objects, but also most of the time, need to see objects at intermediate distances such as blackboards, piano scores, and computer screens. A pair of scientifically customized progressive multifocal glasses can simultaneously meet the needs of distance use, near use, and various distances in between. Some special young myopia patients wearing progressive multifocal glasses can also be used to correct the refractive power and effectively relieve eye fatigue.
The glasses are stylish and have a personality, and the shop decoration has a designer style. A combination of fashion and business, the nose pads are designed with water droplets that are more suited to Asian faces. Breaking the design idea of traditional glasses, the temple is under the glasses, and the arc of the temple makes the face look small. Breaking the bottom half of the frame, the top half of the frame is more designed, with comfortable, thinner lenses.
The function of eyeglasses cloth
Under a powerful microscope, the fibers of the cloth are more closely arranged than those of ordinary cloth, and the material itself is softer than ordinary cloth. That's because eyeglasses under the eye are almost always coated, with each standard lens having seven layers of different functions on the front and back surfaces, to extend lens life. It can thoroughly remove the stubborn stains left on the lens to make the picture clear. It can clean all kinds of glass, resin, and other materials of glasses, glass mirrors, and other mirror surfaces, remove stains, and grease absorption.
How to Adjust Crooked Glasses
If one side of your frame looks higher than the other, you need to adjust the arms of your glasses. So, how to adjust glasses?
If the right side is higher than the left, you need to gently bend the left arm down at the hinge or where the arm bends behind your ear. If the left side is higher than the left, so just do the same action on the opposite side.
When adjusting crooked glasses, you need to adjust frames a little bit at a time to avoid overcompensating and possibly damaging your glasses. You can run the arms under the warm water but do not running the warm water over the lenses because it will affect the lens coating.
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.