CR39 1.50 Standard Index:
This is the most common material in use for spectacle lenses. It’s a basic plastic material that is 50% the weight of glass. It is a soft material so scratches easily therefore at buynewspecs we will provide an anti scratch coat as standard. Note an anti scratch coat improves resistance to scratching rather than making the lens scratch proof.
Anti-reflection or anti glare:
This is a multi layered coating applied to the lens to counteract reflected light e.g. those from a computer screen, overhead fluorescent lights and those from oncoming headlights while driving. An anti reflective coat allows more natural light to reach your eyes thus improving visual performance while making your eyes appear clearer to other people, and improving the cosmetic appearance of your lens. Your anti reflective coat consists of layers the thickness of which is a 100th of a human hair and approximately 13 layers are applied to counteract different spectrums of light. An anti reflective coat increases the surface hardness of the lens therefore providing scratch resistance.
Also known as Transitions or reactions. These lenses lighten and darken according to changes in UV light levels i.e. they darken in sunny conditions and turn to clear when indoors. Photochromic lenses give 100% UV protection and reduce the effects of glare. These lenses come with an anti-reflection coat as standard thus enhancing your visual performance further.
This is a measure of a finished spectacle lens thickness. The higher the index number chosen for your lenses the thinner the finished lenses will be. Standard CR39 has an index of 1.50. As high index lenses reflect greater amounts of light we recommend an anti-reflective coating.
At buynewspecs we have three high index lenses to choose from:
- Thin 1.6 index: This lens is 20% thinner than a basic CR39 lens 4 times stronger than CR39. An anti-reflective coating is included.
- Thinner 1.67 index: This lens 33% thinner than a basic CR39 lens. An anti-reflective coat comes as standard when you choose Extrathin lenses.
- Thinnest 1.74 index: This lens is 43% thinner than a basic CR39. An anti-reflective coat comes as standard when you choose Superthin lenses.
A tint is applied to a lens by immersing it into a bath of a coloured dye solution. The dye penetrates the lens allowing even distribution. Choose from an array of colours and depth of tint to suit, ranging from a light tinting to sunglass dark.
These differ from tinted lenses as they are designed to cut out reflective glare e.g. that glare while driving on a wet road on a sunny day. Did you know that 20% of all light transmitted is reflected from the surface of water while a whopping 80% is reflected from snow? By cutting reflective glare your visual performance is improved, colours appear more vivid and contrast is enhanced. Polarised lenses are ideal for sunglasses (they look the same as a tinted lens), for sports people, water sport enthusiasts, skiers and for driving
This is a lens containing your distance and reading prescriptions in one. A varifocal lens provides a gradual change in prescription from distance power situated near the top right through to arms length or computer correction (at the middle) to close reading at the bottom of the lens. Varifocals are generally only used for people over the age of 40 who need two spectacle prescriptions, one for distance and one for reading. Your spectacle prescription will have an addition also known as ‘add’ or ‘near’ to specify the extra reading power required for your lenses. The lens manufacturer calculates the computer reading power you need therefore this power is generally not included on your prescription. Cosmetically a varifocal looks the same as a standard distance or reading lens but with no obvious reading section. An anti-reflection coating is an option with varifocals.
Note. As varifocal lenses need a period of adaptation we recommend not driving with your new varifocals until you have visited your optician for fitting
This is a lens containing both your distance and reading prescriptions in one. Bifocals are generally only used for people over the age of 40 who need two spectacle prescriptions, one for distance and one for reading. Your spectacle prescription will have an addition also known as ‘add’ or ‘near’ to specify the extra reading power required for your lenses. Cosmetically bifocals are noticeable by a magnified round or letter D shaped section towards the lower part of the frame
Note. As bifocal lenses need a period of adaptation we recommend not driving with your new bifocal glasses until you have visited your optician for fitting.
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