Types of eyeglass lenses according to the material used
In terms of material, there are several types of lenses. Most known are glass lenses, which are known for their good optical properties. Then there are plastic eyeglass lenses - nowadays the most used lenses. Polycarbonate lenses can be seen mostly in different risk profession or is used in sport eyeglasses. Less known are the eyeglass lenses made from Trivex material - a durable material with excellent optical properties. However, it can’t be used at higher diopters.
Types of prescription eyeglass lenses according to the material used
Glass lenses
The characteristics of glass are well-known. Glass is a hard, poorly conductive material, which can crack under rapid temperature changes. In the past, glass was the only material used for lens manufacture. The advantage of glass is very good optical characteristics, high resistance against scratching and thin profile. With diopters of 10 and more and when using glasses with a higher refractive index, it is possible to achieve esthetically very nice marginal thickness.
Plastic material – CR39, Orma 1000
Plastic eyeglass lenses are the most commonly used type of lenses today. They have very good optical characteristics in comparison with mineral glass they are very light and resistant against braking. It is possible to use them in all types of frames and to use all kinds of colors and surfacing. They can be manufactured even with high refractive index, which is suitable for higher diopter. Their slight disadvantage is that they are softer than mineral glass which causes that they get scratched faster.
Polycarbonate
It was developed in 1957 in the USA. In the 60s of the 20th century it was used to manufacture visors on the helmets of astronauts and windows of spaceships in the Apollo programme. This material belongs to a group of thermoplastic materials, which are softer, but a lot more flexible, more impact-resistant than CR39 and other, they have higher refractive index (1.59), thin center thickness, small weight and high resistance against scratching. They also absorb 100% of UV rays. Thanks to these characteristics they have been used for lenses for higher risk jobs and sports.
Trivex
Trivex is the first material used in lenses that combines three very important characteristics – brilliant optical characteristics, excellent impact - and cracking-resistance, and very small weight, which is 10% less than with polycarbonate material. Its disadvantage is that it can be manufactured with refractive index up to 1.53, which means it can't be used with higher diopter, because the profile would be too thick.
