How to buy prescription glasses online
Consumers should choose different styles of frames according to their age and professional characteristics. Because everyone has different face shapes, different interpupillary distances, and different diopters, the size of the frames should vary from person to person.
Lenses are divided into glass lens, resin lens, and PC lens, and you can choose according to your preferences. The glass lens has a stable refractive index, good abrasion resistance, and stable optical performance, but it is relatively heavy and easy to break. Resin lens with high light transmittance is light, safe, and not easy to break, but the surface is easy to wear. PC lens has a high refractive index, but the surface is easy to wear.
Disadvantages of polarized sunglasses
Polarized sunglasses have many benefits. However, in some cases, non-polarized lenses are a safer choice. On cloudy days, drivers find that non-polarized sunglasses are better than polarized sunglasses due to the lack of glare and extreme sunlight.
Driving with polarized lenses after snowing can be dangerous for drivers. As the glare of polarized sunglasses is blocked, ice or snow on the road will not be visible. In this case, the advantages of polarized sunglasses will become the disadvantages that may cause accidents.
In addition, when driving along a dark road with few street lights at night, wearing polarized lenses will make it harder to see the road conditions because they dim the available light better than non-polarized glasses. Of course, in low-light conditions, it is best to avoid wearing sunglasses completely while driving.
The most significant disadvantage of polarized sunglasses is that they do not perform well on digital screens and displays. They can cause the images and information on the LCD screen to blur or disappear at certain angles. Don’t wear polarized sunglasses to use these devices while driving.
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.
The shape of the lens is also important.
Aviator and cat-eye glasses should be avoided, as both will cut off the base of the prescription, resulting in poor reading vision. Instead, they should opt for shorter frames with rounded edges, such as bull horn frames, vintage wingtips, round frames, and oval frames.
How Do Pinhole Glasses Work?
Compared to traditional glasses, pinhole glasses work differently. Traditional glasses correct your vision often by collecting rays of light as they enter the eye and forcing them to converge on the retina rather than behind or in front of it.
However, pinhole glasses limit the amount of light entering your eyes so as to enable people to see more clearly.
Different Types of Progressive Lenses
The first progressive lenses we want to introduce are computer progressive lenses, which are designed for clear vision in office settings. These lenses are ideal when using a computer for over 4 hours a day and help to reduce eye strain.
Computer progressive lenses are intended for indoor use and should not be worn over your regular glasses. The drawback to this is it requires you to have two separate pairs of eyeglasses.
The lens material
Lens material affects the effect of protecting our eyes, so we should choose the kind of driving glasses made of polarized lens, which can effectively reduce the dazzling lights, and can filter out the redundant lights. When used at night, the powerful light is softened and the vision is clearer, thus ensuring the safety of drivers and relieving eye fatigue. If you can, let the seller dim the light when you buy, feel the softness and clarity of the light after wearing the product.
