Spectacles - Lens Technology [back] Lens Types Lens Materials Lens Tints and Coatings

Varilux Lenses www.varilux.co.uk Zeiss Lenses www.zeiss.co.uk Adidas Sports Eyewear www.adidas.com

Lens Coatings and Tints Coatings Plastics and Glass lenses are available with a range of coatings and tints, although not every coating or tint is compatible with every lens material. Scratch Resistant Coatings These are used on plastics lenses to improve their durability and can be combined with tints and anti-reflection coatings. Anti-reflection Coating An Anti Reflection Coating is made up of carefully controlled multiple layers of material that interfere with the way that light travels through the lens.

This eliminates a significant proportion of surface and internal reflections, improving the cosmetic appearance of the lens by reducing ghost rings at the edge of thicker lenses and making the lens appear more invisible.

Because of its glare reducing properties it is especially suitable for driving and working on a VDU screen. It is suitable for both Plastics and Glass lenses and can be used in conjunction with tints and scratch resistant coatings. Essilor can also add a Scotchgard™ coating to most of their Anti-Reflection coatings in order to improve the anti-static properties of the lenses, making them easier to keep clean.

Tints There is a massive range of tints available for plastics lenses, and although the options for glass lenses are more limited it is possible to tint them in both single colour and graduated shades. Single colour tints Plastics lenses are available in a range of standard colours and densities and can be custom tinted for a fashion look to match your frame.

The most common tints are brown and black and can range from very light [to give a soft cosmetic appearance] to densities that are too dark to wear for driving because your colour recognition is affected causing problems with traffic lights.

UV Block

UV protection is important in a pair of sunglasses, but as climate changes occur it is also important to take it into account with respect to our everyday eye protection. A full UV blocking coat can be added to many plastics lenses. UV protection is especially important to Aphakics, people who are exposed to intense bright light [ e.g. mountaineers and sailors ], people on certain medications which increase their sensitivity to UV radiation [ e.g. tranquilisers, antibiotics, oral contraceptives and anti-histamines ] and people exposed to lengthy times in sunlight [ e.g. gardeners ].

Graduated Tints
These are tints which gradually change their colour and/or density from top to bottom.
They are generally tinted darker at the top and fade to lighter at the bottom, giving a very flattering effect.

They can also be tinted with different colours at the top and bottom [e.g. brown at the top and pink at the bottom] and have even been made with all the colours of the rainbow blending from one to another!

Mirror Finish Tints
In the past these tints have only been available as dark sunglasses, with the base lens being tinted a dark colour and then the front surface coated with a mirror finish. The mirror finish has a silver, gold, bronze, blue or red mirrored effect, but all are 'dark' sunglasses. Recently however, a number of manufacturers have introduced a softer mirror finish over the top of a much lighter tint giving a semi-transparent mirror coating which can be extremely attractive. This coating can be used on some thinner, lighter and polarising materials although it is not compatible with photochromic lenses.

Polarising Tints Polarising lenses give excellent protection against glare, making them great for driving by eliminating   reflections on wet road surfaces. Light reflecting off water during activities such as sailing and fishing can place stress on the eyes making polarised lenses especially useful. They are generally available in brown and grey tints, and can be made in standard materials plus some lighter thinner materials making them very suitable for sports sunwear. Photochromic Tints These are lenses which change their darkness depending on the level of UV they are exposed to. They are available in both Glass and Plastics versions, with plastics generally used more as they are lighter and more comfortable to wear. They are generally available in brown and grey versions. Occasionally a manufacturer releases a fun colour too [in the past pink, green and blue have been available], although the power and material range of the 'fun' versions can be very limited.

Plastics Photochromic lenses can be made in a variety of different materials, making them suitable for a wide range of powers. Glass photochromics tend to be made in a standard refractive index, although Zeiss make one which uses a 1.7 index glass

NEW
An exciting new combination Photochromic/Polarised sunglass lens, the DRIVEWEAR™  [more] lens has just been developed. This is a plastics lens with a polarising filter and photochromic element impregnated into the front surface of the lens. When unexposed to UV [ at its lightest ] it has a greenish brown colour with approximately 35-40%LTF, but when exposed to UV it darkens to approximately 15% LTF within 20-25 seconds and the colour changes to a more reddish brown. Other photochromic lenses are not generally recommended for use when driving as they don't darken much inside a car because UV light necessary to make them change is blocked by the materials of the windscreen and side windows. The DRIVEWEAR™ lens is  sensitive to both visible and UV light so when you add in the polarising effect it makes them an excellent sunlens for use when driving.