Overview of Eyeglass Lens Materials
Beginning in the 13th century, Italian monks in Murano, Italy, created magnifying lenses from a type of quartz called Beryl. For years after, lenses for glasses were actually made from crown glass. Glass lenses were replaced by plastic lenses in the 1980s because they were more durable. Today, the most common eyeglass materials are plastics and include CR-39, polycarbonate, Trivex, and high-index.
What to consider while choosing lens materials?
When you choose a lens material for your glasses, consider optical clarity, eye safety, frame selection, prescription, and comfort.
Optical Clarity
Optical clarity is the precise, high-definition quality of your vision. Each lens material has a different clarity because of light transmission, and light scatters through the material. Lens materials have an abbe number and refractive index, which affect lens clarity. Abbe value is a measure of the degree to which light is dispersed or separated when passing through a lens. The higher the abbe value, the better the optical clarity and the less distortion. Though glass lenses have superior optical clarity, they are not often sold in the United States because of their heavy weight and potential safety issues.
Frame Selection
The frame you select should guide your choice of eyeglass lens material. If the frame is metal with a thin side called a bevel, it's important to pick a thinner lens material. Depending upon your prescription, you may have a thick edge to your lens, or the lens may be thicker in the middle. Higher index materials thin the lens and improve its appearance. They reduce the amount of lens visible from the side of your eyeglass frame.
Prescription
If you have a high prescription, eyeglass lens material selection is very important. Higher prescriptions tend to get heavier and affect the appearance of your eyes. Plus lenses will magnify your eyes, causing them to appear larger, while minus lenses will minify your eyes, causing them to appear smaller. Selecting the best eyeglass material is important for an improved appearance.
If you have to wear glasses, you want them to look as nice as possible! The refractive index represents how well a lens material bends light and how fast light travels through the material. The index of refraction determines how light and thin the lenses will be.
Safety
It’s important to consider eye safety and protection when choosing an eyeglass lens material. Legally, all children’s glasses must be made of polycarbonate or Trivex materials. In some cases, doctors may recommend a high-index material to improve the lens appearance so that the child is more likely to wear the glasses.
Patients with reduced vision in one eye should have their glasses made of polycarbonate or Trivex to protect the better-seeing eye.
Comfort
Lighter, thinner lenses are more comfortable. They reduce the weight felt on the bridge of the nose and behind the ears. Heavy lenses may cause impressions on the nose or even headaches.
Lens Material #1: Plastic (CR-39)
The first plastic eyeglass lenses, called CR-39, were developed in the 1940s. CR-39 stand for Columbia Resin #39. CR-39 was the 39th formula of a thermosetting plastic developed by the Columbia Resins Project. The material was made for military planes in WWII. CR-39 plastic lenses are the most basic, inexpensive lens. They are more impact-resistant than glass lenses and have good optics. Although they weigh about half the amount of glass lenses, CR-39 lenses are the thickest and heaviest material and are incompatible with rimless frame styles.
Lens Material #2: Polycarbonate
Polycarbonate is a strong, durable, impact-resistant material. Many items are made from polycarbonate, including medical devices, automotive components, protective gear, greenhouses, digital disks, and lighting fixtures. Polycarbonate lenses became popular after they were first introduced in safety glasses in the 1970s.
For safety, kids', sports, and safety glasses should be made of polycarbonate. Polycarbonate lenses will not shatter if you were to be hit in the face with an airbag or a fast-pitch softball. In addition, polycarbonate lenses have UV protection within the lens material.
Lens Material #3: Trivex
Trivex is a newer material introduced in 2001 and is an alternative to polycarbonate lenses. Trivex lenses have better optics and are less likely to crack than polycarbonate lenses; however, polycarbonate lenses are thinner.
Trivex lenses are cast molded, while polycarbonate lenses are injection molded. Trivex is a lightweight and impact-resistant eyeglass lens material with improved optics. Lenses made from Trivex are extremely resistant to being dropped or scratched. If you select a rimless, semi-rimless, or drill-mount frame, Trivex is the best eyeglass lens material.
Lens Material #4: High-Index
High-index lenses are made of a denser material than standard CR-39 lenses but less dense than glass. The refractive index of high-index plastic lenses ranges between 1.59 and 1.74. The higher the number, the thinner the lens. High-index lenses are much thinner and lighter than regular plastic lenses but are delicate and crack easily. High-index lenses are more expensive but are necessary for patients with high prescriptions.
Comparison table of lens materials
An eyeglass lens material comparison table can aid in selecting a material for your glasses. Each eyeglass lens material has advantages and disadvantages. All lens materials are compatible with transitions and anti-reflective coatings. They are also available in single-vision, bifocal or progressive lenses. Overnight Glasses offers standard and high-index lens material options in 24 hours.
| Lens Material | Refractive Index | Abbe Value | Features | Recommended prescriptions** |
|---|---|---|---|---|
| Super High-index plastics | 1.74 | 33 | The thinnest lenses available. Block 100 percent UV. Lightweight. |
No limit |
| High-index plastics | 1.67 | 32 | Thin and lightweight. Block 100 percent UV. Less costly than 1.74 high-index lenses. |
Up to |8.00| |
| 16X UVEX | 1.60 | 41 | Thin and lightweight. Significantly more impact-resistant than CR-39 plastic and high-index plastic lenses (except polycarbonate and Trivex). Higher Abbe value than polycarbonate. Better Optics |
Up to |6.00| |
| Trivex | 1.53 | 45 | Superior impact resistance. The lightest lens. Great optics! Good for children and sports. Blocks 100 percent UV. Much Higher Abbe value than polycarbonate. |
Up to |4.00| |
| CR-39 plastic | 1.498 (1.50) | 58 | Optically the best lens! Clearest lens material but not as lightweight or impact resistant as Trivex. | Up to |2.50| |
| Polycarbonate | 1.598 | 30 | Thin and lightweight. Significantly more impact-resistant than CR-39 plastic and high-index. Cheaper than Trivex. Good for kids and sport. HC, UV included. | Up to |5.50| |
* Polycarbonate and Trivex materials are similar in strength and impact-resistance.
** Recommended prescriptions value is the absolute value of both your sphere and cylinder.
What is the best eyeglass lens material?
While several options exist in eyeglass lens materials, Trivex lenses are the best eyeglass material for most patients with low-medium prescription strength. Trivex lenses offer the best clarity of vision and are the lightest most impact resistant spectacle lenses. If eye safety is vital for your occupation or hobbies or you are ordering glasses for a child, Trivex lenses are also best for eye protection.
If you have a higher prescription strength then High-index materials are your best option. These materials will keep your lens weight low, improve the appearance of your eyes through the lens and the appearance of the lenses inside the frame, no matter which frame you choose.
