Understanding Prescription Lenses

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Single-vision lenses
The simplest form of spectacle lens is the single-vision lens, made to a single prescription to correct a particular eyesight problem. Concave lenses are used to correct short sight and convex lenses to correct long sight. Concave lenses are generally thinner in the centre than they are at the edge and convex lenses are usually thinner at the edge than at the centre. The curvature of the lens, its thickness and weight will depend on the amount of long or short sight it is designed to correct. The lens material will also influence the thickness and weight of your lenses, as will the size and shape of the spectacle frame you choose. Traditionally, spectacle lenses were made of glass but most lenses are now lightweight plastic and there is a wide range of materials available to suit your prescription and lifestyle.

Bifocals
Bifocal lenses contain two optical corrections with a distinct dividing line between the two parts. The most common use of bifocals is for people who have become presbyopic and need a different prescription for close work. The upper part of the lens corrects distance vision and the lower half is for near vision. Trifocals are also available that have three sections and incorporate a correction for intermediate vision. Bifocals and trifocals come in a range of designs but nowadays varifocal lenses are much more likely to be prescribed.

Varifocal or progressive lenses
Varifocal lenses, also known as progressive lenses, are used for correcting presbyopia but unlike bifocal lenses have no visible dividing lines between the different corrections. Instead they have a graduated section in which the power of the lens progresses smoothly from one prescription to the other, allowing the wearer to see clearly at all distances. These lenses also have the benefit of looking better - they dont draw attention to the ageing process. A range of varifocal designs is available depending on your lifestyle and occupation. Modern lens technology means that there are many different designs and materials to choose from. We are happy to advise you on your individual requirements, please feel free to phone or email for advice.

High-index and aspheric lenses
If you need high-powered lenses you can improve the weight or appearance of your glasses with special lens materials and designs. High-index materials and aspheric designs mean that lenses can now be made thinner, lighter and better looking than traditional lens types. High-index materials make lenses for short sight thinner, while aspheric designs that minimise the amount of material make lenses for long sight both thinner and lighter.

HIGH INDEX - 1.60 Index
A thin lightweight lens ideal for the short sighted wearers
- Up to 30% lighter than standard 1.5 index CR 39 plastic
- Hard coated to resist scratching
- Multi anti-reflection coated for enhanced night driving
- UV protection up to 380nm
- Good cosmetic appearance ( Smaller frames give a slimmer appearance with minus prescriptions )
*THIS LENS IS ALSO NOT SUITABLE FOR TINTING

HIGH INDEX - 1.67 Index
A slimmer lighter lens for short sighted wearers
- As much as 25% slimmer than the 1.60 index lens
- Aspheric design reduces chromatic aberration and edge distortion giving good all round vision
- Hard coated to resist scratching
- Multi anti-reflection coated for enhanced night driving
- UV protection up to 380nm
- Good cosmetic appearance ( Smaller frames give a slimmer appearance with minus prescriptions )
*THIS LENS IS ALSO NOT SUITABLE FOR TINTING

HIGH INDEX - 1.74 Index
The thinnest lightest resin lens available today
- As much as 35% slimmer than the 1.60 index lens
- Aspheric design reduces chromatic aberration and edge distortion giving good all round vision
- Hard coated to resist scratching
- Multi anti-reflection coated for enhanced night driving
- UV protection up to 380nm
- Good cosmetic appearance ( Smaller frames give a slimmerr appearance with minus prescriptions )
*THIS LENS IS ALSO NOT SUITABLE FOR TINTING

Lens Thickness Comparison -6.00 +4.00
1.50 Index Our standard lens is single vision 1.5 index Cr 39 plastic resin and is adequate for most people
1.56 Index The tensile strength of this index is lower than any other in general, although some brands have overcome this problem. It is slightly thinner than 1.50 but its lack of strength renders it unusable for Rimless.
1.60 Index Our lowest priced thin lens.
1.67 Index Our mid priced thin lens.
1.74 Index The thinnest plastic lens available.

Prescription sunglasses
Whatever your prescription, it is important to protect the eyes against excessive ultraviolet (UV) radiation. Protection is needed to avoid reflected light from sand and snow or if you spend long periods out of doors, particularly in the summer. Prescription sunglasses can be made with single-vision, bifocal or varifocal designs to offer the same standard of protection as non-prescription sunglasses.

Anti-reflection coating
Spectacle lenses can be provided with anti-reflection coatings which virtually eliminate distracting reflections off the lens surfaces. Reducing reflected light is particularly helpful for computer users and for night driving. Anti-reflection coatings also improve the cosmetic appearance of your glasses and can make thick lenses look thinner.

Scratch-resistant / hard coating
Plastic lenses are lighter than traditional glass lenses but they scratch more easily. Scratched lenses can be irritating for the wearer and look unsightly. Scratch-resistant coatings are available to protect against damage and prolong lens life.

Multi-coated lenses
Multi-coated lenses incorporate a combination of coatings - anti-reflection, scratch-resistant, water repellent and UV - to combine to improve the properties of your spectacles.

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