Which Type of Lens Material Is Right For Your Glasses?
When choosing lenses for your glasses, it is good to know what lens material is most suitable for your lifestyle and most importantly, your vision.
There are a variety of great lens materials available for eyeglass wearers. In recent years, advances in technology have resulted in breakthroughs that now allow people to enjoy lenses that combine all the best advantages – UV protection, impact resistance, excellent optics and the lightest materials. See below the different lens materials that are available, along with the advantages and disadvantages of each.
1) High-index plastics: The thinnest and lightest lenses available. They are highly recommended if you have a strong eyeglasses prescription for nearsightedness, farsightedness or astigmatism.
2) Polycarbonate: Lightweight lenses are extremely impact resistant and also offer UV protection. A suitable choice for both children’s glasses and safety glasses.
3) Trivex: Similar to polycarbonate lenses, Trivex lenses are thin, lightweight and much more impact-resistant than regular plastic or glass lenses. However, they offer crisper vision and a higher Abbe value than polycarbonate lenses.
4) CR-39 plastic: These lenses are half the weight of glass lenses and still provide excellent optics and vision correction; however they are generally thicker than other plastic lens options.
5) Crown glass: Glass lenses will always provide the best optical experience as glass refracts light much more efficiently than plastic; however, they are heavier and thicker than their plastic counterparts.
Index of Refraction
The refractive index of an eyeglass lens material is a number that measures how well the material refracts and bends light, which depends on how fast light travels through the material.
Basically, the higher the refractive index of a material, the slower light moves through it, which results in a greater bending (refracting) of 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 any eyeglass prescription, 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.
In addition, high-index lenses tend to be more expensive because they are of higher quality than low-index lenses.
The Abbe value of a lens material is a way to measure how widely the lens disperses different wavelengths of light as light passes through it. Lens materials with a low Abbe value have high dispersion, which can cause noticeable chromatic aberration, which is an optical error visible as colored halos around objects, especially lights at night.
The Abbe value of lens materials available today can range from a high of 59 (crown glass) to a low of 30 (polycarbonate). The lower the Abbe value, the more likely the lens material is to cause chromatic aberration.