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.
How to test a blue-light lens?
Blue-light-blocking lenses are now focused on refractive indices of 1.56 and 1.60. If you buy lenses that are not of either refractive index, be wary. Of course, with the development of technology, now some brands have produced 1.71 refractive indexes blue-light-blocking lenses, suitable for people with high myopia to wear. The true lens package should at least have the product name, refractive index, dispersion coefficient, transmittance, color, SPH, CYL, and other indicators. These indicators are perfect, can be treated as the reference basis of the formal product. In addition, you can go to a professional optical shop or testing institutions for testing.
Can you look at your phone while wearing polarized sunglasses?
That's because polarized lenses filter the light from some phones, leaving only black stripes visible.Polarized sunglasses have polarized lenses, and cell phone screens have polarized patches in their components. The polarized film has the function of shielding and passing through the incident light, which can make the longitudinal light or transverse light one kind of passing through, one kind of obscured. Because different phones have different polaroid settings, there will be different shades at different viewing angles. Thanks to a combination of polarizing lenses and lenses, both of which filter the direction of light, the screen can't be seen when the shielding and penetrating parts overlap.
What effect does a lens with the hard film have?
In order to improve the wear resistance of the lens, it is necessary to coat the surface of the lens with hard film. At present, silicon atoms are used to stiffen the membrane, that is, the stiffening solution containing organic matrix and inorganic superfine particles including silicon element is used to make the hard film have toughness and hardness at the same time. Because the common resin lens is far easier to wear than the glass lens, so the addition of hard film is mainly used for resin lens. It is usually applied to the front surface of the lens, and the anti-wear ability of the resin lens with the film will be enhanced a lot, and the light permeability will be strengthened.
Why is a prescription for glasses different from a prescription for contact lenses?
The frame glasses degrees are the optometric degrees of the eye, and the difference between the frame glasses degrees and the contact lens degrees is mainly due to the different contact distances between the two lenses and the eye. Usually, degrees of contact lenses and glasses need to be converted by a professional through vertex diopter. The conversion formula is Fc=Fs/(1-d×Fs). In the formula, Fc is the diopter of contact lens, Fs is the diopter of glasses frame lens, and D is the distance between frame glasses lens and cornea. Assuming that the prescription of frame glasses is -4.00d and the distance between lens apex is 12mm, the prescription of contact lenses is -4.00/ [1-0.012×(-4.00)] = -3.82d.
How to Choose Reading Glasses?
If you need reading glasses when using a computer, you may want to choose a lower reading glasses power. This is because most people view their screen from a greater distance from their eyes than when they are reading a book or a magazine.
However, if you need reading glasses for looking at something very close or very small, you may need a pair of stronger power glasses.
In most cases, when two reading glasses’ powers seem equally suitable, choose the glasses with the lower power. Picking reading glasses that are too string typically will cause more discomfort problems than reading glasses that are a little too weak.
Characteristics of Carbon Fiber Glasses
Carbon fiber frames have pretty impact resistance. Carbon fiber is made of carbon, the core element of diamonds. It is ten times stronger than iron, and it weighs less than steel. The maximum stress it can withstand before breaking is 7 to 9 times that of steel. Carbon fiber is more resistant to corrosion than metals like titanium. It has high-temperature resistance, radiation resistance, good elasticity. Carbon fiber is not only flexible, but durable, so it won't break if you drop it. Carbon fiber has many benefits, including high stiffness, high tensile strength, low weight, high chemical resistance, high-temperature resistance, and low thermal expansion.
