Lens Coatings Explained

There are a number of lens coatings that will improve the performance of the lens and clarity of vision. The more expensive the glasses or sunglasses, the more likely it has several layers of coatings. The coatings and the reasons for them are listed below.

All lightweight lens materials (plastic, polycarbonate, and high index plastics) have a relatively soft surface.  These materials require a SRC to be applied to both sides of the lens. Glass lenses do not require a SRC.  Because of its natural hardness, glass is even more scratch-resistant than most lightweight lenses with SRC applied. The majority of prescription lens packages offered by eyekit.co.uk include a SRC coating.

As light passes through a spectacle lens, a percentage of it is reflected back from the surface of the lens, rather than being passed through the lens. With standard spectacle lenses this represent about 8% of light that is reflected back. Light can also be reflected off the back surface of lenses, towards your eyes, especially in situations where you are under overhead fluorescent lighting, or when driving at night with other car's headlights around you. These reflections cause glare, which is uncomfortable, and also reduce the contrast of what you are looking at, making objects less easy to see.

An anti-reflective coating will reduce these reflections to about 1% making your lenses clearer to see through, helping to reduce eye strain and eye fatigue. For example, computer users get the comfort of improved contrast and less harsh glare.

Together with the action of ventilation systems the AF coating permanently bonded to the inside of the lens absorbs moisture before fog forms. It can fade over time with repeated cleaning of the inside of the lens. As an alternative, there are now many effective sprays and wipes that can be used to reduce lens fogging.

This treatment weakens surface tension to facilitate run-off of water droplets from the lens surface. It reduces visual distortion arising when wearing glasses or sunglasses around water or in the rain. It also resists stains and repels grease and fingerprints, so cleaning your lenses is quicker and easier.

Clear lenses can be enhanced to provide additional protection from UV rays. Without significantly changing the colour of the lens, a treatment can be applied that will prevent UV light from reaching your eyes, reducing the risk of certain eye disorders such as the formation of cataracts and macular degeneration.

To provide 100% UV protection, glass and plastic lenses must have UV coating applied. This is not necessary for polycarbonate, NXT and most high index plastic lens materials as they block 100% UVA, UVB and UVC without the need for added coatings.

UV can be sub-divided as follows:

UVC - Wavelengths below 280nm are effectively filtered out by the ozone layer surrounding the earth. The amount of absorption varies and is less near to the equator and at high altitudes due to the reduced atmospheric thickness.

UVB - Wavelengths between 280nm and 315nm; responsible for sunburn and snow blindness. The amount of ultra-violet affecting a person is substantially increased by reflection from surfaces such as snow, sand and water.

UVA - Possibly the most dangerous area, between 315nm and 380nm, potentially causing chronic eye damage to the eye, especially low dose exposure over a long period of time.

Beyond UV there is HEV - HEV stands for high-energy visible light, which appears besides UV radiation. You will see this light as a bluish purple. The usual range of HEV light is 380 to 470 nm and upwards. There is currently a debate about the effectiveness of Blue Block coating on lenses. 470nm upwards is essential for balanced living and its absence may be the trigger of seasonal depressions. We do offer a Crystal Blue Block coating that will provide addition protection to 440nm.

If you click on the ‘more info’ button within the prescription package options, it will provide information on the level of UV protection for the specific package selected.

Multi-Coated Lenses offered by Eyekit

Listed below are the multicoated lens options offered by Eyekit that include a number of coatings explained above designed to meet specific customer needs. 

Our Crystal multicoated anti-reflection (MAR) range – with hydrophobic, anti-static, blue-block and oleophobic properties – are comparable with many of the best branded coated lenses on the market today. MAR lenses allow more light to reach the eye over standard lenses and the more light that reaches the eye the better the vision. With standard spectacle lenses only about 92% of the light that reaches the spectacle lens reaches the eye. The reflections you see in a standard lens are the 8% of light being ‘bounced’ back off the lens. With our Crystal range of anti-reflection lenses, over 99% of light passes through the lens. So you can see almost zero reflections ensuring more light reaches the eye to improve vision. 

Some of our prescription packages include additional coatings and will include words such as ‘Crystal Vision’ at the end of the package title. We have included these multi-coatings as we feel that they are a minimum requirement to ensure you receive the best vision from the type of lens package you have selected. Multi-coating options available:

Crystal Vision - A multi-layer anti-reflective coating on both sides of the lens with hydrophobic top coat applied over a hard coat to give excellent visual performance and durability. Key benefits:

• Scratch Resistant Coating - Reduces scratching and abrasions over time, keeping the lens clearer for longer and maximising vision quality and useful life of the lens over non coated lenses.
• Anti-reflective Coating - Prevents those annoying reflections, eliminating interference glare and ghost images, reducing eye strain and improves vision.
• Hydrophobic Coating - This water repellent coating is similar to a wax coating on a car, it helps to shed water droplets and avoids smudging. Also, water is not attracted to the lens surface in humid conditions (steam, condensation etc). Ideal for outdoor use such as playing football on rainy days or for spray when sailing.

Crystal Clean - Premium Multi-layer anti-reflection (MAR) coating on both sides of the lens combines the benefits of Crystal Vision with the addition of ultra-smooth oleophobic and anti-static properties to facilitate lens cleaning. Key benefits:

• Scratch Resistant Coating - Reduces scratching and abrasions over time, keeping the lens clearer for longer and maximising vision quality and useful life of the lens over non coated lenses.
• Anti-reflective Coating - Prevents those annoying reflections, eliminating interference glare and ghost images, reducing eye strain and improves vision.
• Super Hydrophobic Coating - Premium performance coating. This water repellent coating is similar to a wax coating on a car, it helps to shed water droplets and avoids smudging. Also, water is not attracted to the lens surface in humid conditions (steam, condensation etc). Ideal for outdoor use such as playing football on rainy days or for spray when sailing.
• Oleophobic Clean Coat - This oil repellent coating makes removing perspiration, greasy finger marks, smudges, and dirt much easier, keeping your lenses clearer and cleaner for longer.
• Antistatic Coating - Repels dust and stays clean. Electrostatic charges are eliminated by a conductive layer within the MAR coating, minimising the attraction of dust.
• UV Protection - Added rear surface UV protection.

Crystal Blue Block - Specifically designed to give added comfort and protection to users of LCD and LED screens, by filtering out blue light from selected wavelengths. Crystal Blue Block provides  enhanced comfort, more relaxed vision and better contrast perception to the wearer when using everyday digital devices. Key benefits:

• Scratch Resistant Coating - Reduces scratching and abrasions over time, keeping the lens clearer for longer and maximising vision quality and useful life of the lens over non coated lenses.
• Anti-reflective Coating - Prevents those annoying reflections, eliminating interference glare and ghost images, reducing eye strain and improves vision.
• Hydrophobic Coating - This water repellent coating is similar to a wax coating on a car, it helps to shed water droplets and avoids smudging. Also, water is not attracted to the lens surface in humid conditions (steam, condensation etc). Ideal for outdoor use such as playing football on rainy days or for spray when sailing.
• Antistatic Coating - Repels dust and stays clean. Electrostatic charges are eliminated by a conductive layer within the MAR coating, minimising the attraction of dust.
• Blue Light Filter - Reduces eye fatigue, eye strain and even sleeplessness. It keeps the eyes in better condition, offering more comfortable and relaxed vision and a better contrast perception when using everyday digital devices such as phones, computer screens and TV’s.

Crystal Drive - Includes additional coatings that are optimised for driving, offering improved comfort in all driving conditions during the day and reduces dangerous glare from oncoming vehicles at night. The coatings reduces the overall amount of blue light entering the eye and the addition of a slight gold filter also improves brightness. Key benefits:

• Scratch Resistant Coating - Reduces scratching and abrasions over time, keeping the lens clearer for longer and maximising vision quality and useful life of the lens over non coated lenses.
• Anti-reflective Coating - Prevents those annoying reflections, eliminating interference glare and ghost images, reducing eye strain and improves vision.
• Hydrophobic Coating - This water repellent coating is similar to a wax coating on a car, it helps to shed water droplets and avoids smudging. Also, water is not attracted to the lens surface in humid conditions (steam, condensation etc). Ideal for outdoor use such as playing football on rainy days or for spray when sailing.
• Blue Light Filter - Reduces eye fatigue and eye strain from light reflections during the day and car headlights at night. It keeps the eyes in better condition, offering more comfortable and relaxed vision and a better contrast perception while driving.

Crystal Clear - A colourless ant-reflective coating suited to users who prefer their eyes to be seen. This coating is designed to provide maximum visual comfort with a very high level of light transmittance of 99.7%. Key benefits:

• Scratch Resistant Coating - Reduces scratching and abrasions over time, keeping the lens clearer for longer and maximising vision quality and useful life of the lens over non coated lenses.
• Anti-reflective Coating - Prevents those annoying reflections, eliminating interference glare and ghost images, reducing eye strain and improves vision.
• Hydrophobic Coating - This water repellent coating is similar to a wax coating on a car, it helps to shed water droplets and avoids smudging. Also, water is not attracted to the lens surface in humid conditions (steam, condensation etc). Ideal for outdoor use such as playing football on rainy days or for spray when sailing.
• Oleophobic Clean Coat - This oil repellent coating makes removing perspiration, greasy finger marks, smudges, and dirt much easier, keeping your lenses clearer and cleaner for longer.
• Antistatic Coating - Repels dust and stays clean. Electrostatic charges are eliminated by a conductive layer within the MAR coating, minimising the attraction of dust.

 Mirror lenses are good for situations that require a reduction in the overall brilliance of light, such as sunlight on snow. They reflect light away from the eye (beyond the standard absorption of a tinted lens) which is ideal for people who are light-sensitive.

Applied to the surface of the lens only, it gives the lens a shiny mirror-like appearance that reflects rays from surfaces such as water, snow and ice. They are typically applied in combination with an underlying sunglass tint. Metallized coatings offer fashion versatility because they can be applied as flash mirrors with only a blush of reflectance, as full mirrors that mask the eyes or as gradient mirrors.

The density of the mirror coating determines how much light it reflects.  Half-silvered mirror coatings have an even coating of reflective particles across the surface of the lens, but the particles are spaced so about half of the light striking the lens surface hits a coating particle and is reflected.  The remaining 50% of visible light striking the lens passes between the reflective particles.  Some of this light is absorbed by the underlying lens tint.  The remainder passes through the lens to the eye.

Mirrors are available in several basic styles. Solid mirrors are a classic sunwear look, especially in silver, gold and blue. Gradient mirrors being the densest at the top of the lens, and then fading to nothing at the middle of the lens provides maximum shading of overhead sunlight, while allowing more light to pass through the middle and lower parts of the lens. This is beneficial for drivers and cyclists or people who like to read outdoors. Double gradient mirrors are also functional. They are dark at the top and the bottom and lighter in the middle. Double-gradient mirror coatings are an excellent choice for snow skiing and other winter activities because they provide excellent protection from both overhead sunlight and light reflecting off snow on the ground.  

Long term durability and abrasion resistance can be improved with the addition of a hard coat and hydrophobic coating. Also, back reflectance will be more noticeable with a mirror, especially on darker lenses. An AR coating on the back surface is strongly recommended. All prescription mirror packages offered by eyekit.co include these coatings.

A range of coloured tints can be applied to most lenses, from standard sunglass tints through to specialised tints for activities such as shooting and comfort tints for night time driving. Lenses can also be tinted to various colours that in some cases aid reading for people with dyslexia. For further information, read the article ‘Tint’s Explained’ under sunglasses in the Information Resource on the left of this page.

If you require a specialist tint for your lens, eyekit.co have made it easy to specify. Just select the prescription lens package you require, go to the tint section as prompted, choose your tint and then the category of tint. For example, if you want a comfort tint or to aide reading with dyslexia, choose category 1 (a light tint), or for shooting in sunny weather, choose a category 3 tint. You can find further information on lens categories in the Information Resource.