High-index lenses are thinner and lighter, so they’re great for stronger prescriptions. They help avoid thick, bulky lenses, giving you a more comfortable and stylish look.
Polycarbonate lenses are light, tough, and protect against UV rays. They’re perfect for active people, kids, or anyone who needs lenses that can handle a little extra wear and tear.
Mid-index lenses are thinner and lighter than standard lenses, perfect for moderate prescriptions. High-index lenses are even thinner and lighter, designed for stronger prescriptions. If you're shopping for lenses, Eyeglasses Direct and Glasses direct are nice options.
Common spectacle lens materials include glass, plastic (e.g. CR-39), polycarbonate, and high-index materials. Each material has its own advantages and disadvantages in terms of durability, weight, clarity, and cost. Polycarbonate lenses are often recommended for impact resistance, while high-index lenses are thinner and lighter than standard plastic lenses for higher prescriptions.
Standard index 1.5 lenses Standard index 1.5 lenses are the basic CR-39 lenses, come with anti-scratch hard coating, and are shatter-resistant, suitable for spherical power +/- 2.00 or below, and cylindrical power +/- 1.50 or below. Index 1.57 mid index spherical lenses Index 1.57 spherical lenses are with anti-scratch hard coating. This higher index lens greatly reduces the thickness of the lens edge. This is suitable for spherical power of +/- 4.00 or below with cylindrical power +/- 2.00 or below. Index 1.57 mid index aspherical lenses Index 1.57 aspherical lenses are even thinner and lighter than 1.57 spherical lenses. These lenses come with anti-scratch and anti-reflective coating, greatly reducing the image distortion, suitable for spherical power of +/- 4.00 or below, and cylindrical power of +/- 2.00 or below. High index would be anything greater than the 1.57 lenses, like 1.61 or 1.67 and so on. Each having a degree of benefits and drawbacks unique to it's making.
1.57 mid index single vision lenses means that the lens is thinner than standard plastic lenses. It is not the thinnest possible, nor is it impact resistant like Trivex 1.53 mid index lenses, or polycarbonate. It will be thinner than either of those materials. Single vision means that there is one range of vision. If a bifocal lens is not prescribed, then this is what the vision is. When the prescription is a bifocal prescription, then either distance only or reading only must be chosen.
Polycarbonate lenses are a popular choice for rimless eyeglasses because they’re lightweight and durable, but they’re not the only option. High-index lenses and Trivex lenses are also great choices for rimless frames, offering a balance of strength and comfort. EyeGlassDirect has a variety of lens options to suit your needs and style.
Half of the difference between the two positions is called the "index error".
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The index of refraction varies for different colors of light (i.e., for different wavelengths or frequencies), therefore, a source of white light, like rays from the Sun, can get separated into their components. White light isn't "pure" (monochromatic) light - it is really a mixture of many different colors.
Viscosity is resistance to flow of oil Viscosity Index is a scale to measure viscosity
A glossary defines words, while the index tells what pages certain topics are on in the book.
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