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.
What Is Trivex Lens?
Trivex is another light, impact-resistant eyeglasses lenses. Like polycarbonate lens, Trivex is an excellent lens material for safety applications and children’s eyewear.
Trivex lenses are made of a urethane-based monomer. They are produced using a slower, cast molding process similar to how regular plastic lenses are made. The liquid lens material is slowly baked until is set. This gives Trivex lenses the advantages of sharper optics than injection-molded polycarbonate lenses.
Are metal or plastic eyeglass frames better?
Experts agree that many materials of sunglasses will be targeted, with a high focus on the specific combination of materials used. The frame of your glasses depends on whether you want a stylish or mature look. You can wear different glasses for different situations and clothes. Metal sunglasses are suitable for formal situations or mature types of people, and not easy to damage. Plastic sunglasses are usually more diverse, and the design is changeable. They can be used for a variety of sites. They are suitable for each age group and can be selected according to your actual situation.
How Long Does It Take to Get Used to Varifocals?
When you get a new pair of glasses, you have to get used to them. So, how long does it take to get used to the glasses? Some people only need a couple of days to get used to them while some others may need up to two weeks.
It is normal if you can only see the frame rim of your glasses when you first wear them. The reason for this lies in the brain’s visual center. It needs to adapt the new and greatly improved visual conditions.
How to clean the lenses?
When wiping lenses (especially the rimless glasses of resin lens), you must use a special wipe lens or soft handkerchief or paper. When you wipe the lens, you can only wipe it in one direction, not in circles, and don't touch the lens with your fingers. When the lens is stained with dust and sand, it should be washed with water before wiping, otherwise, the lens is likely to be abraded, and the operation should be gentle. At ordinary times, when cleaning, do not exert too much force, pay attention to the grasp of strength. When wiping the lens, it is best to take the side frame with one hand, and the other hand takes the glasses cloth to wipe gently. In order to prevent the lens film layer falls off, do not use alkaline detergent to wipe the lens. Therefore, when bathing or playing at the seaside, glasses should be properly kept to avoid water vapor or seawater caused by corrosion of glasses.
How to test a blue-light lens?
When the glasses are placed in front of a display screen or watched in the environment with LED light, the blue-light-blocking lenses reflect blue lights, while the non-anti-blue lenses do not reflect blue lights. Of course, there are a small number of blue-blocking glasses that reflect green lights.
How to Choose Reading Glasses?
Choose big frames the first time. When choosing reading glasses, you can choose the big frames for the first time. You may need larger glasses frames or lenses to really get the sweet spot of where the prescription is.
And if you have never worn glasses for eye conditions such as nearsightedness, farsightedness or astigmatism, it is likely you will be able to see well with non-prescription reading glasses. So, you can buy these non-prescription reading glasses.
