How to buy contact lenses online?
Choose the right contact lens for your situation. Base arc and degree need to be added in the hospital or optician shop to determine. Try not to buy according to the framed degree. Some businesses claim to have the lenses having South Korea's silicone hydrogel, with annual throwing. They are not to be believed, because the material characteristics of the silicon hydrogel are not capable of making long-time discarded type lenses. There are a lot of things to pay attention to in order to properly wear contact lenses. For example, a medical optometry sheet is the premise of attention. Each pair of contact lenses is marked on the package of the basic arc, diameter, water content, diopter, and other parameters. Only according to the optometry sheet, you can choose the correct basic arc, diameter, and diopter. At the same time, there is a certain distance between the glasses and the cornea.
Common Problems with Varifocal Glasses
In this section, we will list some common problems with varifocal glasses. The most common problem with varifocal glasses is people being unable to focus on what they need to. Losing focus often leads to some discomforts such as headaches or dizziness when performing tasks that require quick changes in near and middle-distance focus.
Besides, some people also experience a sort of swimming feeling when they are walking. It may be caused by being very aware of the distortions in your peripheral vision as well as the reading portion at the lower part of the lenses.
So, how to use varifocal glasses? The best way is to keep yourself from looking downward as you walk. You may also experience soft focus at the edges of the lenses and need to move your head more to see near objects better.
Eyeglasses Holder Strap Cord
It uses a reinforced anti-slip clamp ring. With an oversized metal clip and top-quality PU leather around the neck, this eyewear holder strap will provide stylish features. Unlike other eyewear cords, it will not make you look old. They are suitable for all types of glasses, from small frames to large frames. These eyewear chains and wires are suitable for both men and women, providing universal compatibility. They are suitable for reading glasses and magnifying glasses. You will have a stylish bag and cleaning cloth.
What Is a Prism in Glasses?
Prism is triangular and made of plastic or glasses for the purpose of dispersing light into a spectrum or changing the direction in which light is reflected.
Prism lenses are special lenses that are prescribed by eye doctors and infused into regular lens prescriptions. The prism glasses do not include contain any focusing power, and therefore cannot any refractive errors. So, one of the most common uses for prism glasses is to correct diplopia or double vision. Double vision means someone sees two separate images of a single object. The prism glasses help to align the two images and correct the problem. The prism glasses can be used to improve binocular vision and reduce double vision, headaches, reading difficulties, and so on.
What is the function of eyeglasses holder straps?
If your glasses are loose or slip off a lot, or if you have an active lifestyle, the eyeglasses holder straps can be very helpful. This simple device is designed to help you track your glasses and keep them from falling off. Retailers sell eyewear holder straps in a variety of designs, materials, and colors.
Clean your glasses correctly.
The dust of the lens will be washed (lightly), and then use a neutral detergent (cleaner) to clean. You can also buy professional glasses cleaning fluid, finally clean by water, and then use a professional glasses cloth to wipe. If the lens is covered with dust and particles before wiping, it is best to wash it with water and then gently dry it with a cloth.
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.
