Lenses & Coatings
Lenses & Coatings
All of our prescription glasses are priced including standard lenses.
Our standard lenses are the same as those provided by the vast majority of opticians and are made of a lightweight plastic material known as CR39. For more information there is a Wikipedia page detailing the properties of this material and why it became the popular choice for making scratch resistant lenses.
Lens types - At a Glance
|Type||Index||(Relative)||± 2.00||± 4.00||± 6.00||UV||Unbreakable|
Lens thickness when compared to standard index.
Estimated centre thickness of a plus power lens or edge thickness of a minus power lens in specs of a standard size with an average pupil distance.
The vast majority of spectacles sold in Britain make use of a light weight plastic lens material known as CR39. Unless you are otherwise aware then this is most likely the type of lens you have in your specs, it is perfectly suited for optical use and offers excellent image quality and a good compromise between impact resistance and scratch resistance. Our standard lenses are available with a Hard anti Reflection coating (see below).
Standard CR39 lenses are suitable for all types of frame though for rimless glasses we recommend high index or polycarbonate lenses.
High Index lenses
High Index lenses are plastic lenses which have been processed in a way that makes them better at bending light (or refracting), hence the term refractive index.
The higher the refractive index, the thinner a lens will be for a given prescription.
If your prescription has values over +/- 3.00 then there is much to be gained cosmetically from high index product. High index lenses are stronger than standard lenses and as such are a better option for rimless frames.
Thin 1.6 index are approximately 20-25% thinner than standard.
Superthin 1.67 index lenses offer a thickness saving of approximately 30% over standard index.
Ultrathin 1.74 index,the thinnest plastic lenses on the market, 35-40% thinner than standard lenses.
Our high index lens options are supplied with a Hard Anti Reflection coating as standard as well as blocking out harmful UV or Ultra Violet light.
Polycarbonate 1.59 Index
Polycarbonate lenses are our preferred choice of lens for rimless glasses as it is a virtually unbreakable lens material. It is also extremely light weight and with an index of 1.59 it offers much of the thickness saving of a high index lens. We supply our Polycarbonate with an anti scratch coating as standard as the qualities which make a lens less brittle also render it less hard and therefore more prone to scratching. Polycarbonate lenses are also available with a Hard Anti Reflection coating (see below).
Photochromic is a generic term used to describe a lens which darkens under bright light. Our photochromic lenses are made from a mid index material, 1.56 index, so they offer improved cosmetics. Under bright sunlight the lenses will darken fully in approximately 15 seconds, out of sunlight they will fade back to almost clear in a matter of minutes. Photochromic lenses are available in Brown and Grey.
Transitions are the market leading Photochromic lens and are available in Brown and Grey. They have a lighter residual hue when unactivated, generally less than 10% and barely noticeable. Transitions react faster than most other brands of photochromic although we feel it sensible to point out that if you have seen the adverts on TV look out for the small print in the corner of the screen stating that the reaction has been sped up for the sake of demonstration!
Hard Anti Reflection coating
All plastic lenses have inherent scratch resistant properties.
With our Hard Multilayer Anti Reflection (HMAR) coating Your lenses will benefit from added Scratch Resistant properties as well as Anti Reflective properties. No plastic lens is scratch proof however so care should be taken when handling and cleaning lenses.
Our HMAR process will make your lenses as resistant to scratches as is possible. It is the hardest coating that can be applied to a lens. We would advise caution when being seduced by claims of 'free anti scratch coating'. There are a number of ways of increasing the scratch resistance of a lens, some of which will not provide a notable increase nor a permanent one.
Our anti Reflection coating also includes an Easy Clean layer, this makes the surface of the lens super smooth and as well as easy to like, less likely to attract smears and smudges in the first place.
From an Anti Reflection point of view there are various benefits.
Spectacle lenses reflect light.
If you are surrounded by many light sources, for example in an office environment, then these can produce distracting reflections on the surface of your lenses.
Up to around 8% of the light reaching uncoated lenses will be reflected but with an Anti Reflection coating this is often reduced to under 1% thus vastly diminishing the effect.
This also results in better cosmetics as your lenses appear clearer to onlookers.
Prolonged exposure to Ultra Violet Radiation can cause damage to the eye.
All of our High Index, Photochromic and Polycarbonate lenses offer excellent protection against UV, blocking in the order of 99% of harmful Ultra Violet Radiation up to 400nm.
Cleaning your lenses
Your new specs will reach you in a protective case complete with a microfibre cleaning cloth. Keeping your lenses in tip top condition is simple.
- Keep your specs in their case when not in use.
- Only clean your specs with the cloth provided or a similar clean cloth intended for this purpose.
- Clean your specs once a week in soapy water and dry with a tissue.
The biggest culprits when it comes to spectacle damage are car dashboards and handbags, follow the simple rules above and your new purchase will serve you well for years to come.