Information Resource

Lens Materials Explained

The material used in your glasses or sunglass lenses will affect their clarity, durability weight, and cost. Below are the main advantages and disadvantages of the various lenses available on the market.
 
Glass Lenses
 
Originally, all lenses were made of glass, which while it made them very resistant to scratching, also made them very heavy and prone to breakage. These lenses are now becoming obsolete with the exception of toughened lenses for industrial safety glasses.
Advantages: Lens Material Explained- Glass Lenses Prescription Glasses, Sunglasses and Goggles for Sports watersports travel urban fashion golf cycling biking shooting for men and women
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Lens Material Explained- Plastic Lenses- CR39 Prescription Glasses, Sunglasses and Goggles for Sports watersports travel urban fashion golf cycling biking shooting for men and womenPlastic Lenses – CR39
 
CR 39® is the most common optical polymer in the ophthalmic field. It refers to the type of plastic that is used to make prescription lenses. The lens comes from pouring the liquid polymer into a mould of optically treated glass. This enables to obtain a lens with the same characteristics of the originating glass. It provides very little distortion (more than glass but less than polycarbonate), it is more lightweight and thinner than glass making it comfortable to wear and it is more impact resistant though it may still break and shatter upon impact.  As such, it is not recommended for active sports.
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 Lens Material Explained- Polycarbonate Lenses- Advantages and Disadvantage Prescription Glasses, Sunglasses and Goggles for Sports watersports travel urban fashion golf cycling biking shooting for men and womenPolycarbonate Lenses
 
Polycarbonate is one of the strongest and safest materials on the market. They have exceptional strength and resilience. They will survive the impact of a steel ball travelling at 160 km/hr without shattering which meets EN/EU grade for Low Energy Impact Resistance (small particle).
Our entry level glazing packages offered for our rimless and semi-rimless glasses are polycarbonate lenses. Due to the nature of these types of frames where the lenses have to be drilled or clipped into the frame, polycarbonate will greatly reduce the possibility of damage.
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Lens Material Explained- NXT Lenses- Advantages and Disadvantage Prescription Glasses, Sunglasses and Goggles for Sports watersports travel urban fashion golf cycling biking shooting for men and womenNXT  Lenses
 

NXT was originally created in the USA for military applications as a new bullet-proof, transparent and light-weight material capable of providing superior protection, reliability and longer lasting performance than polycarbonate. It is a unique material that combines the advantages of CR39, Mid-Index lenses and polycarbonate, but leaves out all their inherent weaknesses. In fact it is a lens without weakness! It is the best material for mild to moderate prescriptions.

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 Lens Material Explained- Mid to High Index Plastic Lenses Thin and Lite Prescription Glasses, Sunglasses and Goggles for Sports watersports travel urban fashion golf cycling biking shooting for men and womenLens Material Explained- Mid to High Index Plastic Lenses- Super Thin and Lite Prescription Glasses, Sunglasses and Goggles for Sports watersports travel urban fashion golf cycling biking shooting for men and womenMid to High Index Plastic Lenses –Thin and Lite and Super Thin and Lite
 
Mid and high index lenses are for people with a high prescription. They allow spectacle lenses to be made thinner, lighter and flatter than previously possible. They are compressed lenses that offer better optical viewing through them. For higher prescriptions they not only reduce the weight by up to 50% but also reduce the thickness by up to 60% making them more attractive cosmetically. In addition to making the glasses look cosmetically better, they will feel lighter on your nose, and the flatter shape of the lens will make things look less distorted towards the edges of your lenses.
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Lens Material Explained- Aspheric Lenses Prescription Glasses, Sunglasses and Goggles for Sports watersports travel urban fashion golf cycling biking shooting for men and womenAspheric Lenses

Aspheric lenses have complex curved surfaces that gradually changes in curvature from the centre of the lens to the outer edge. Whereas conventional lenses have a front surface that is spherical, meaning it has the same curve across its entire surface, much like a football. The key benefits of aspheric lenses compared to spherical lenses are listed in the table below.

 

What if I buy Aspheric designed lenses that are high index (Thin & Lite or Super Thin & lite)?

The combination of an aspheric design with high-index lens materials creates a lens that is noticeably slimmer, thinner and lighter than conventional glass or plastic lenses.
 
Free-form Design
 
 
‘A new technology that could change the way you see—forever.’

Called ‘free-form’ these lenses are Aspheric. However using the latest free-form technology, they are cut using a digital design manufacturing process that takes into consideration over 40,000 points across the lens enabling lenses to be produced with 0.01D power accuracy. This gives lens designers the ability to reduce lens aberrations even more than they are using conventional lens design and processing techniques.
 

What are the benefits of Free-form lenses?

The benefits of Free-Form lenses- Lens Material Explained- Prescription Glasses, Sunglasses and Goggles for Sports watersports travel urban fashion golf cycling biking shooting for men and womenMany leaders in the vision industry expect free-form technology to be the next revolution in vision correction. Lighter and thinner than standard lenses they provide exceptional night/low light vision reducing glare and halo effects from car headlights. They also offer exceptional contrast perception sharpening vision and improved colour rendition providing brighter and more intense colours.
 

Will I benefit from Free-form Lenses?

To use an analogy, it is similar to comparing high-definition television with the old analog TV picture quality. All of a sudden the old TV
seem drab and blurry. High-definition TV makes colours brighter, shapes sharper, and brings everything keenly into focus. Now imagine having the same experience with your glasses. Of course, you can see fine with the ones you have, just like watching analog TV was fine when that was all you had.
However, while everyone can benefit to a certain extent from free-form lenses, since these lenses are usually made with more aberration and distortion control and improved power accuracy, individuals with higher eyeglass prescriptions will notice greater benefits than people with only mild prescriptions.

They also benefit people with complex prescriptions and those that select frames with higher base curve lenses which are more complex to produce. If you order an 8 base wrap prescription from Eyekit we will only offer free form lenses for this reason. By using free form lenses we can ensure they will provide good vision across the whole curvature of the lens and avoid the optical distortions that can occur in the periphery area of vision with standard lenses.

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