Lens Materials

Although choosing your spectacle frame is generally thought of as the fun part of getting a new pair of spectacles, unless you get the right type of lens inside it, all the time and effort that you've taken getting just the right look can be wasted.

Because of this, at Leslie Warren and Linklaters we make sure that our Dispensing Opticians and Assistants are available to help you make an informed choice from the wide range of materials and designs that are available.

Nowadays, lenses can be made in a wide range of materials to make them thinner, lighter and more comfortable to wear, as well as improving the cosmetic aspect of your finished spectacles.

As everyone uses their spectacles in different environments and for different purposes, there is also a range of coatings which can be used separately or in combination to improve the visual performance of your eyewear. And of course with the increase in awareness of the importance of protection against UV we can advise on the type and transmission value of tints from the most subtle cosmetic shading, funky fashion tints and polarising tints to the dark tints required for use in high altitude /snow conditions.

So no matter whether your spectacles are a single power [for driving or reading] bifocal or multifocal there is a choice of options available.

CR39
This is the world’s most popular and commonly used plastics or 'organic' lens material.
It is lightweight, tough and much safer than glass. It weighs far less than the equivalent glass lens and is very easy to tint, making it suitable for some of the more fashionable  and fun custom tinting as well as being made in photochromic, polarising tints and with mirror finishes. We do recommend a hard coating to increase scratch resistance, but lenses can be supplied uncoated if you wish. They are also suitable for the many types of anti-reflection coatings that are available nowadays. CR39 is available in the widest variety of lens designs, with an enormous range of single power, bifocal and multifocal styles being produced.

High index organic materials.
Polycarbonate lenses are lighter and thinner than a standard CR39 lens and are especially suitable for people who enjoy an active or demanding lifestyle, combining durability, improved impact resistance and comfort.

They can be coated with an anti-reflection coating or tinted with both standard and polarising filters for use during sports or as sunglasses, and are also available with a photochromic option, come with a hard coating on both surfaces as standard and are available in single power, bifocal and multifocal options. Because of their 100% UV protection block and their high impact resistance we recommend these lenses for sports use [tennis, netball, cycling, skiing, sailing, windsurfing and field sports] and for children’s spectacles, as well as for use in rimless frames.

Other High Index Materials The lens manufacturers are working all the time to develop new lens materials in order to improve the cosmesis , comfort and optical performance of their lenses, and over the last few years have developed a number of new organic lens materials with differing refractive indices. Generally the higher the refractive index of a material the thinner it is, although there are other parameters which affect the finished thickness. We can now supply single power lenses and multifocals in refractive indices of 1.6, 1.67, 1.7 and 1.74 [the very thinnest organic lens material]

Glass.

Crown glass is one of the materials used for optical lenses, and before the introduction of CR39 it was the most usual material that lenses were made from. However, due to its heavier weight and more restricted lens sizes, as larger spectacles became popular in the 70's it became less used and was rapidly overtaken by the lighter and more comfortable organic lens materials. It is produced from alkali-lime silicates containing approximately 10% potassium oxide. It has low refractive index (≈1.52) and low dispersion (with Abbe numbers around 60). It is still available as single power, bifocal and multifocal [although in a reduced number of designs], and can be vacuum tinted and anti reflection coated.

There are a number of other high index glasses available which although they do not reduce the weight of the lens can significantly reduce the thickness of a mid to high power spectacle lens.

Most lens manufacturers make at least one version of high index glass lenses in both single power and multifocal options, with Zeiss making glass lenses in up to 1.9 refractive index. With the Zeiss Lantal® 1.9, we can reduce the edge thickness of your lenses by as much as 40% [the thinnest glass lens material available]