Eyeglass lenses have been a staple in correcting vision impairments for centuries, and they continue to be one of the most effective methods for vision correction today. One of the key components of spectacles is the lenses, which come in a variety of materials and designs to meet the specific needs of each individual. In this article, we’ll take a closer look at the different types of lenses for eyeglass frames & sunglasses.
First and foremost, it’s important to understand the basics of how prescription glasses lenses work. Simply put, they help to refract light in a way that corrects vision problems. If a person has nearsightedness, for example, their eye has trouble focusing on distant objects. A concave lens can be used to help bring the light into focus on the retina, thus improving the person’s vision. On the other hand, a person with farsightedness needs a convex lens to help bring the light into focus.
Different types of Lenses for Glasses
One of the most common materials used for prescription glasses lenses is plastic. This is because plastic lenses are lightweight, durable, and affordable. Additionally, they can be tinted to provide protection from the sun or to simply make a fashion statement.
Types of plastic lenses:
- Standard plastic
Because of its high optical quality and lightweight, standard plastic ( which is also known as hard resin or CR-39) is the most commonly used lens material. These are almost 50% lighter than glass lenses due to the low specific gravity of their material. They offer UV protection and can be tinted glasses as well. However, these are prone to get scratches, so a scratch-resistant coating is advised by optometrists.
- High impact plastics
Polycarbonate was the first discovered plastic in 1950. It has low specific gravity and a high refractive index which makes it lightweight and thin. Polycarbonate lenses are durable and meets high-velocity impact standards.
It offers a high amount of chromatic aberration, particularly in high prescriptions which produce unwanted glare. Like CR-39, it can be scratched easily, so it needs a protective layer.
Trivex, a new material, delivers strong optical performance and provides clear vision as it has a high abbe number.
- Hi index lenses
A lens with a refractive index of more than 1.60 is called referred to as a high-index lens. These can be either glass or plastic and are most commonly used for high prescriptions to create thin and cosmetically attractive lenses. The weight, optical clarity and impact resistance of these lenses vary depending on the specific material used and the refractive index. In General, as the refractive index increases, the thickness of the lenses decreases and the clarity of the vision decreases. Hi-index lenses also require a protective coating.
Another popular lens material is glass. Glass lenses offer excellent optical clarity, but they are heavier and more fragile than plastic lenses. In recent years, glass lenses have become less common due to the availability of high-quality plastic lenses.
In addition to the material, glasses lenses can also be designed in a variety of ways to meet different needs. For example, bifocal lenses are designed with two different prescriptions in one lens, which can help those who need both near and far vision correction. Another type of lens is the progressive lens, which gradually changes in prescription from top to bottom to provide a seamless transition from distance to reading vision.
There are other specialized types of lenses for glasses. For example, those who spend a lot of time in front of a computer may benefit from computer lenses, which are designed to reduce eye strain and fatigue. Sports enthusiasts may benefit from prescription eyeglass lenses that are impact-resistant or polarized to reduce glare.
Eyeglass lenses are a critical component of vision correction. With a variety of materials and designs available, there is a lens type to meet the needs of each individual. If you’re experiencing vision problems, consult with an eye care professional to determine the best lens type for you