Although many practitioners actively prescribe multicoated spectacle lenses, it’s apparent that too many don’t. You just need to look around at what the average person on the street is wearing!
There are many options when it comes to coatings including, among others, multicoats, tints, hardcoats, UV and blue blockers, hydrophobic and grease/deposit resistant coatings.
Some are applied to make plastic lenses more resilient and scratch resistant, while others improve wetting, reduce fogging or greasing. Some have antistatic properties to resist attraction of dust, dirt and other contaminants. Others protect the eyes from harmful rays.
There are numerous application methods and technologies: We have dip, vacuum and plasma coats, dyes and more.
A top class premium lens coating involves high tech, time consuming, expensive steps and processes
Many coatings are ‘invisible’ and unless the benefits are explained, patients are unlikely to know about them or request them. This is an opportunity lost, making the lens coating discussion one that’s important to have with every patient.
Each manufacturer has their own proprietary coatings, systems and products and actively promotes multiple benefits. Product listings will help you decide on the merits and benefits of the various offerings, but in the meantime let’s reflect on some of the technologies and offerings available.
One of the coatings that strives to make a spectacle lens ‘invisible’ is the so-called multicoat. An antireflection multicoat is something that clearly improves cosmesis, visual function and optical performance. Aside from reducing annoying and unsightly reflections from the surface, the reduction in internal reflections that cause nasty looking ‘power rings’ is significant. Patients wearing antireflective lenses also often comment that they don’t see reflections of their eyes and lids on the back surface of the lens as well as other irritating reflections from light sources and objects behind them.
For these reasons, a multicoat should be prescribed wherever possible and indeed, many practitioners don’t even discuss the option these days; it’s simply part of the price and package.
If you do need to convince a patient of the benefits of a multicoat, a quick demonstration will usually do the job.
One of the best ways to demonstrate the benefits is to make up a few pairs of demo spectacles and have sample lenses to hand. A +2.00D Rx can be done in a rimless frame with one anti-reflection multicoated lens and one basic uncoated lens. The difference is usually quite marked. It’s also worth having a demo pair in a higher minus lens (like a -9.00D) with one lens in a low index uncoated option and the other in a 1.74 index aspheric multicoated lens.
Single layer anti-reflection coatings, also known as quarter wave coatings, are usually a quarter of the wavelength of the mid range of the visible light spectrum. The quarter wave coating sets up out-of-phase destructive interference that cancels out the reflected wave (much like noise cancelling headphones cancel out stray noise), which dramatically neutralises reflections. By their nature, such coatings do have a ‘bloom’, which is a tendency to have a slight colour sheen that is irritating to some. The colour of the bloom can be shifted by selecting the wavelength used.
Modern broadband anti-reflection coatings however, offer the benefit of attenuating reflections over a wider range of the visible light spectrum, as well as being better able to control the bloom.
Some patients complain that their multicoated lenses ‘get dirtier’ or ‘grease up more’ than their usual uncoated lenses. This is best countered by explaining that the perception results from the fact that there are less reflections to ‘hide’ the dirt: A more perfect optical surface makes these imperfections more visible. Considering that these coatings are high tech and measured on the nano-scale, they stand up very well to normal use. However, like any fine optical surface, they should be properly cared for. A microfiber cloth and spray cleaner or sachet of pre-moistened cleaning pads designed for the purpose, should be recommended and supplied. Patients should be told not to clean the lenses when dry and dusty. They can also be rinsed under lukewarm water and carefully dried.
Deposit Resistance and Other Coatings
A top class premium lens coating involves high tech, time consuming, expensive steps and processes, hence these lenses come at a premium compared to the basic, cheapest lenses on the market.
To understand where the costs come in, it’s probably best to walk through the processes involved.
A high-quality lens surface is a base requisite. A highly polished generated lens or a moulded lens is the first step. To maintain accuracy and a high-quality surface in moulded lenses, the moulds are usually replaced after a certain number of lenses are manufactured.
Lens surfaces need to be scrupulously clean and this requires manufacture in high-pressure, filtered environments with laminar flow workstations. Lenses are then cleaned with solvents, dried and may be bombarded with ‘ion guns’. This ensures good adherence when the hard coatings and UV coatings are applied. Broadband, multilayer anti-reflection coatings are then applied in a vacuum. As mentioned, the multilayer approach is used to control the bloom and cover a range of anti-reflection properties. Ion bombardment may again be applied to harden these coatings. Anti-static treatment/layers may also be applied. Finally, the surface may be treated with a super-slick clean coat, hydro and oleo-phobic layer. This makes for easy cleaning and grease resistance. The anti-static treatment will reduce tendency for dust, dirt and other contaminants to adhere to, or be attracted to, the surface as mentioned previously.
Some lenses may have all the aforementioned coatings while other, more basic options may simply be ‘hard coat plastic’ or include UV protection. Tinting can also be included, either as a solid tint or gradient tint, and /or with polarised or safety options. These days most lenses include full UV blocking. For frequent users of digital devices, we should also consider ‘blue blocking’ filters. These are selective band-pass filters that target the more risky high-energy visible (HEV) part of the blue light spectrum. Blue blocking filters may protect the eye from these potentially damaging rays and show promise in allowing a more normal circadian rhythm and improved sleep cycles.
Check out the following offerings from suppliers to appreciate the multitude of benefits that will appeal most to you and your patients.
Lens Options to Suit Your Patients
Shamir Glacier Plus UV: A durable, comfortable, antistatic and hydrophobic multi-coated lens with UV protection on both the front and back surface. Includes extra UV protection to prevent harmful rays from being reflected into the eyes. With a Bayer rating of 19, Shamir claims this is the most scratch resistant coating on the market with improved smudge resistance.
Shamir Glacier Achromatic UV: All the benefits of the advanced Shamir Glacier Plus UV, with the addition of improved anti-reflection, for anti-reflective and bloom free lenses. Hydrophobic, oleo-phobic and anti-static to keep lenses free of dust, grease and water stains, and easy to clean. Also highly durable and scratch resistant, with great clarity.
Shamir Glacier Blue-shield UV: Protects eyes from harmful HEV blue light and has UV protection on both the front and back surface.
Shamir Glacier Sun UV: A new lens coating for sun wear that provides maximum protection and visual comfort.
Contact: Shamir (AUS) 1300 553 465
Satin Blue: Protective coatings selectively filter light to comfort and protect eyes from harmful blue light while looking at digital screens. Scratch, smudge and water resistant, and dust repellent, these lenses offer great clarity and are ideal for everyday use, regardless of the environment.
Satin UV: A protective coating on the back of the lens helps prevent harmful rays that enter from the front and side, protects the eyes from UV and minimises eyestrain and headaches associated with sun glare.
Contact: CR Surfacing (AUS) 03 8795 9111
Rodenstock Road Sun lenses provide the optimal combination of enhanced contrast and natural vision in traffic. These lenses feature a specially developed 75 per cent brown tint with contrast-enhancing effect, combined with Solitaire Protect Plus 2.
One hundred per cent roadworthy, signal lights (e.g. traffic lights and brake lights) can be perceived clearly. Additionally they offer full sun protection with 100 per cent UVA / UVB blocked.
Contact: Rodenstock Account Manager
Bonastar’s blue light blocking lenses protect patients’ eyes from harmful blue light, reduce eye strain and fatigue, and prevent wrinkles and cataract associated with premature aging.
Bonastar’s premium Crizal Prevencia lens is tinted blue. This lens blocks blue light and helps reduce glare. It repels smudges, water drops and dirt, and is scratch resistant.
BlueEase stock lenses in 1.56 and 1.6 index (pictured)[are specifically designed to absorb harmful blue light and come with a normal clear finish.
Contact: Bonastar (AUS) 02 9310 1688
Hoya Diamond Finish: Independent tests1 proved Hoya Diamond Finish to be the most durable and easiest-to-clean coating available.
The tests were using a system developed in cooperation with the Lens Advisory Board, an American organisation recognised by the Vision Council Technical Committee.
The highly accurate test, which simulates real-life wearer experience, showed Hoya Diamond Finish to be over 29 per cent more durable than the second-most durable coating tested; the easiest to clean (preserves its dust, dirt, water and grease-repellent properties even after long use and repeated cleaning); and the world’s hardest premium coating for scratch resistance.
Hoya Diamond Finish comes with BlueControl to neutralise blue light emitted by digital screens and UV Control.
EnRoute Driving Lens: Soon to be released, this new lens has an exclusive glare filter that noticeably reduces glare by cutting high-energy visible light from LED and Xenon headlights of oncoming traffic, streetlights and on-board equipment. It also significantly minimises distracting reflections while improving contrast and brightness perception in low-light conditions.
The contrast-enhancing filter available on the EnRoute Pro greatly improves contrast and colour perception, and offers next level glare reduction.
All Hoya premium coatings are guaranteed for three years.
1. NSL Analytical Services, August 2015
Contact: Hoya Account Manager
Zeiss lenses with DuraVision BlueProtect attenuate blue light in the range from 390 to 440nm, without compromising the positive properties of blue light in the range from 450 to 500nm. This lens coating reflects a portion of high energy blue light, for clearer and comfortable vision in high blue light emitting environments.
By combining DuraVision BlueProtect with lens designs incorporating Zeiss Digital Inside Technology, wearers experience greater visual comfort and reduced digital eyestrain. This lens also features anti-reflective coatings for superior hardness, anti-static properties and ease of cleaning.
Contact: Zeiss Account Manager
Essilor Smart Blue Filter brings with it the evolution of blue light filtering technology. This clear lens coating cuts up to three times more blue-violet light than standard prescription lenses, without changing the look of your patient’s spectacles.
Smart Blue Filter offers the same blue-violet light filtering as Crizal Prevencia, so it can be used as a safe-guard against the sun’s blue light for patients at risk of age-related macular degeneration or for the added contrast and comfort of your digital device users.
Crizal Prevenica was the first selective blue light filter. It reflects away 20 per cent of the specific blue-violet light between 400 and 455nm, while allowing through the wavelengths around 470nm, (blue-turquoise), that are essential for our circadian rhythms.
Crizal UV is the first and only lens coating to bear the Cancer Council logo for its property of blocking UV reflected off the back surface of lenses. Every Crizal UV lens sold helps fund vital research in the fight against cancer.
Contact: Essilor Account Manager