How many degrees of myopia do I need to wear glasses?
Students are the most nearsighted because they need to read and study every day. Many people have myopia during their student days. During the physical examination, everyone will check their eyesight first. Generally speaking, if the visual acuity is lower than 0.6, it means that you may be near-sighted to 0 degrees. At this time, you need to go for optometry to see the specific vision situation and see if you need to wear glasses. If the visual acuity tested exceeds 200 degrees, you must wear glasses at this time. If you do not wear glasses, your vision will be greatly affected, and the degree of myopia will rise quickly. For this reason, you must wear glasses in time to correct your vision. If the degree of myopia does not exceed 0 degrees, this is pseudo-myopia and does not require glasses. However, you should always take care to protect your eyes, avoid staring at things at close range for a long time, and don't let your eyes get too tired, so your vision will slowly return to normal.
What kind of glasses can people with round faces choose?
Always thought, like what has been said on the Internet, if you wear black frame glasses with large lenses, they can make you look small on the face. This is a mistake, because the black frames are too obvious, creating the wrong area on your face where the glasses are too small.
And for this kind of rimless glasses, because the bottom part is transparent, they will not destroy the partition, and you will feel the face is pretty sharp. For a man with a round face, the appropriate choice is a flat or pear-shaped frame. For a woman with a round face, in principle, she should avoid choosing any very obvious characteristics of the frame, and should not choose a too round or straight-line frame. Round faces are suitable for slender or square frames or pear-shaped frames. The human face of a round face is shorter, so, they had better match the slender glasses frame that takes curve slightly to reconcile the whole feeling. The square glasses or the frame with angle, are helpful for modifying the facial ministry line, highlighting the longitudinal line.
What kind of glasses are bifocals?
Bifocals are mainly used in presbyopia correction, providing presbyopic opticians with a clear vision for both near and far use in one pair of glasses. The bifocal lens can be divided into two separate areas, with the upper part of the lens providing clear distance vision and the lower part providing clear near vision. The two regions of the bifocal lens provide different refractive forces, and the difference between these two refractive forces is the reading proximal addition, which compensates for adjustment during presbyopic reading.
What Are Anti-Glare Glasses?
Anti-glare glasses are made with lenses that have an anti-glare coating or anti-reflective coating. This is an extremely thin layer placed on the lens itself so as to remove any reflections you might see from the surface of the glasses. This improves your vision by reducing the amount of glare that reflects off of your lenses.
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 refractive index of lens
Refraction law is discovered by Dutch mathematician Snell.It is the law that determines the direction of refracted light in the phenomenon of light refraction. When the light from the first medium (refractive index N1) into the second medium (refractive index N2), part of the light from the first medium into the second medium at the smooth interface will be refracted. The index of refraction is the ratio of the speed at which light travels in a vacuum to the speed at which light travels in the medium. For glasses lenses, the higher the refractive index, the thinner the lens, that is, the lens with the same center thickness and the same degree, the lens with the higher refractive index has thinner edges than the lens with the lower refractive index of the same material.
Is a nose pad become green harmful?
Pure copper rust contains bacteria that affect the skin and can cause breakouts or skin irritation. High-end glasses are made of alloy materials with lead and nickel not exceeding the standard. Low-end and cheap glasses may not contain environmentally friendly alloy, which will do harm to the human body if it rusts.
