Testing of aspheric lens
The optical axis of the optical center just overlaps with the visual axis of the eye, which is the most ideal state. Because the light from the edge cannot form a focus on the optical axis, when the optical axis does not overlap with the visual axis (the difference is greater than 2mm), such unclear and scattered imaging results will occur. When choosing frames and aspheric lenses, you need to ensure that they fit correctly, to achieve the best visual and decorative effects. Simply put, due to the special design of the lens, we found through a calculation that the optical center should move down 1mm higher than the pupil for every 2° increase in front inclination angle. Otherwise, the wrong pupil height will cause the lens to look like astigmatism, and cause discomfort. For glasses with aspheric lenses, there must be an inclination angle after wearing. The specific angle varies from person to person.
Why is it risky to get glasses online?
The safety and professionalism of online lens matching are widespread concerns of consumers. The whole process of online lens matching is networked, and only a prescription sheet for online lens shopping cannot provide comprehensive and detailed feedback on patients' eye conditions. Therefore, there will be many safety concerns about myopia, high myopia, and astigmatism when they choose to choose glasses online. They have to think about that if the products are qualified, if the quality is good if the style is consistent with the real thing, and so on.
Shorter lens beam
When you choose a glasses frame for kids, you must pay attention to that the lens beam must be short. The size of the lens beam stipulated by the national standard is 13~22mm. As a child, it should be controlled under 18mm. Otherwise, the position stability of the glasses will be poor.
Finally, they can not casually wear other people's glasses. The strength of each person's glasses, the distance between the optical centers of the two lenses, the length of the temple are different. So they can not casually wear other people's glasses.
What is an MR lens?
MR is the brand name of optical lens raw materials produced by Mitsui Chemicals in Japan. MR series is available in three different refractive indices (1.60, 1.67, 1.74): MR-7, MR-8, MR-10, and MR-174. MR-7 and MR-10 have higher thermal deformation temperature and excellent dyeing, which are widely used in the field of sunglasses. MR-8 has the most balanced performance index and is suitable for the production of lenses of any strength. It has the highest market share in lens materials with a refractive index of 1.60. MR-174 is a high refractive index lens material, which is mainly used in the production of ultra-thin lenses.
Visionworks
Visionworks is a leading provider of eye care services dedicated to providing their customers with a wonderful shopping experience and high-quality products and services with the best value and selection in the industry. All stores provide designer and exclusive branded frames, lenses, sunglasses, and accessories as well as leading vision correction technology. Every purchase comes with an unconditional 30-day satisfaction guarantee and free lifetime cleaning and adjustment.
The TR90 Spectacle Frame
TR90 frame is a kind of polymer material spectacle frame with memory, no chemical residue is released, and it meets European requirements for food-grade materials. It is currently an internationally popular ultra-light spectacle frame. TR90 frames have the characteristics of super toughness, impact resistance and abrasion resistance, and low friction coefficient, which can effectively prevent damage to the eyes and face caused by the breakage and friction of the frame during sports. Because of its specific molecular structure, it has good chemical resistance, is not easy to deform in high temperature environment, can withstand high temperature of 350 degrees in a short time, and is not easy to melt and burn. Moreover, the TR90 spectacle frame has a lubricating surface with a density of 1.14-1.15. It will float when placed in salt water. It is lighter than other plastic spectacle frames. It is about half the weight of the sheet frame and 85% of the nylon material. It can reduce the burden on the bridge of the nose and ears.
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.
