These lenses are significantly thinner and lighter than regular plastic lenses. They have a higher index of refraction and are available in an aspheric lens design see below for more about these. Here are popular eyeglass lens materials, arranged in order of refractive index and lens thickness pretty good indicators of cost.
Except for the crown glass, these are all plastic materials. The index of refraction or refractive index of an eyeglass lens material is an indicator of how efficiently the material refracts bends light.
This efficiency is related to how fast light travels through the material. Specifically, the refractive index of a lens material is the ratio of the speed of light in a vacuum, divided by the speed of light in the lens material.
For example, the index of refraction of CR plastic is 1. The higher the refractive index of a material, the slower light moves through it, which results in greater bending or focusing of the light rays. So, the higher the refractive index of a lens material, the less lens material is required to bend light to the same degree as a lens with a lower refractive index. In other words, for a given eyeglass lens power, a lens made of a material with a high refractive index will be thinner than a lens made of a material with a lower refractive index.
The refractive index of the most popular eyeglass lens materials used today ranges from 1. For the same prescription power and lens design, a lens made of CR plastic will be the thickest and a 1. The Abbe value of a lens material determines how much chromatic aberration the lens produces. This is an optical error that causes colored halos around lights.
Chromatic aberration is most noticeable when looking through the periphery of eyeglass lenses. It is least noticeable when looking directly through the central optical zone of the lenses. Abbe values of eyeglass lens materials range from a high of 59 regular glass to a low of 30 polycarbonate.
The lower the Abbe number, the more likely the lens material is to cause chromatic aberration. Abbe number is named after the German physicist Ernst Abbe , who defined this useful measure of optical quality. Glasses lenses with an aspheric design have a slimmer, more attractive profile than regular lenses. In aspheric lenses, the curvature of the lens changes gradually from its center to its edge.
This enables the use flatter curves when fabricating eyeglass lenses. Because aspheric lenses are flatter than regular lenses, they cause less unwanted magnification. This makes the wearer's eyes look more natural in size and appearance. In some cases, aspheric lens designs also improve the wearer's peripheral vision. Most high-index plastic lenses are aspheric to optimize both appearance and optical performance. With polycarbonate and CR lenses, an aspheric design is optional and available for an added cost.
In the United States, the U. For this reason, there's a limit to how thin an optical laboratory can grind your lenses. In lenses for the correction of myopia, the thinnest part of the lens is the optical center, located at or near the middle of the lens. The thinnest part of eyeglass lenses that correct farsightedness is at the edge of the lenses. Because of their superior impact resistance, polycarbonate and Trivex lenses can have a center thickness of just 1. Myopia-correcting lenses made of other materials usually have to be thicker in the center to pass the standard.
The size and shape of your eyeglass frames also will affect the thickness of your lenses. This part of the process typically takes between days to arrive, but we will keep you informed all the time with tracking information.
And, finally, we offer assistance and help even after the sale too! We wear our customer service like a badge of honor and always strive to make buying prescription lenses easy, convenient, and as affordable as possible! In most cases, you can put old lenses into new frames, as long as the frames are of the same type and size as the ones you used to have.
An optician would have to double-check to ensure that your prescription doesn't affect the eyewear you use so that you are less likely to have potential problems in the future. We recommend seeing if your old prescription lenses are scratched or chipped before fitting them into new frames. This is because we take our eyeglass lens replacement job seriously at rx-able.
However, we do not recommend reusing old lenses. This is because your eyes and how they react to specific types and strengths of lenses change over time, meaning that you need to get an eye care professional to test your eyesight every two years or earlier when you notice problems such as constant headaches, soreness eyes, or blurry vision.
Competition has been rising over the last few years to get eyeglasses lens replacements for your new or old frames — and not only from brick and mortar stores but also from online optics retailers.
Rx-able offers an attractive solution to getting affordable prescription lenses into frames that you'll love to wear. We custom cut and fit every pair of lenses to fit your exact prescription requirements and desires.
Our passionate team can assist you through the entire process, so you are informed at every step of your eyewear journey to end up with a new pair of glasses that will protect your eyesight and show off your style. Not only do we succeed in this, but we provide the absolute best when it comes to customer care and offer you quality lenses at a fraction of the price of physical retailers. Be sure to get in touch if you have any questions, and sign up for our FREE newsletter to be informed of useful advice regarding prescription eyewear, money-saving tips, and more!
We have created a chart to make it easier for you to shop for replacement lenses. What Is The Process? Our Process All you need to do is choose your lens design and material by browsing through our selection on rx-able. Shop Replacement Lenses. Share Tweet Pin. High Index Lenses Thickness Comparison:. This example shows the difference in thickness for high index lenses. High Index Lenses Are Thinner:.
High index lenses are much thinner due to their ability to bend light. As they bend light more than an ordinary lens they can be made much thinner but offer the same prescription power. High Index Lenses Are Lighter:. As they can be made thinner, they contain less lens material and are therefore much lighter than ordinary lenses. These benefits will increase the higher the index lens option selected.
The more the lens bends light, the thinner and lighter it will be. With fewer reflections, more light passes through the lens to the eye for good vision and the lenses look more transparent and attractive. Anti reflection coating is especially beneficial when used on high-index lenses, which reflect more light than regular plastic lenses.
Anti-reflective coatings allow Anti-reflective glasses also are more attractive, so you can look your best in all lighting conditions.
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