The advantages of anti-reflective coatings
In addition to improving vision, anti-reflective coatings (also referred to as “AR coatings” or “anti-glare coatings”) enhance the appearance of your glasses and reduce eye strain. As a result of AR coating, you will virtually eliminate reflections from the front and back surfaces of your lenses, resulting in these benefits.
Having reduced reflections in your lenses allows more light to pass through them, allowing for optimal visual acuity and fewer distractions (especially during the night), and the lenses appear nearly invisible, enhancing your appearance by drawing attention to your eyes and allowing you to engage with others more effectively.
The AR coating is particularly beneficial when used on high-index lenses, as high-index lenses reflect more light than regular plastic lenses. Generally speaking, the higher the index of refraction of the lens material, the more light that will be reflected from the surface of the lens.
Plastic lenses, for example, reflect approximately eight percent of the light hitting them, resulting in 92 percent of available light reaching the eye. High index plastic lenses can reflect up to 50 percent more light than regular plastic lenses (approximately 12 percent of available light), resulting in even less light available to the eye for vision.
In low-light conditions, such as at night, this can be particularly problematic.
Today’s anti-reflective coatings can virtually eliminate the reflection of light from spectacle lenses, allowing for the passage of 99.5 percent of available light into the eye.
As a result of eliminating reflections, AR coating also makes your spectacle lenses appear nearly invisible, enabling people to see your eyes and facial expressions with greater clarity.
You can also look your best in all lighting conditions with anti-reflective glasses.
When wearing spectacle lenses with anti-reflective coatings, you will be able to see clearly at night with less glare and you will be able to use the computer for longer periods of time without discomfort (compared with wearing spectacle lenses without AR coating).
AR coatings are applied to photochromic lenses to enhance the clarity and comfort of these premium lenses under all lighting conditions without compromising their sun-reactive ability.
As well as sunglasses, anti-reflective coatings are also an excellent choice, since they eliminate glare caused by sunlight reflecting into your eyes from the back surface of tinted lenses when the sun is behind you. Because there are no cosmetic or visual benefits associated with eliminating reflections from the front surface of dark-tinted lenses, AR coating is generally applied only to the back surface of sunglass lenses.
“Hydrophobic” surface treatments repel water, preventing the formation of water spots on the lenses. The surface treatment seals the anti-reflective layers and makes the lenses easier to clean.
It is possible to make anti-reflective lenses with both hydrophobic and oleophobic surface treatments (also called lipophobic), which means that both water and oil are repellent. These combination treatments typically contain fluorinated materials that give the lenses properties that are very similar to those of nonstick cookware.
Application of anti-reflective coatings
It is a highly technical process that uses vacuum deposition technology to apply anti-reflective coatings to spectacle lenses.
During the AR coating process, the lenses must be meticulously cleaned and inspected for visible and microscopic surface defects. Even a smudge, piece of lint or hairline scratch on the lens can result in a defective coating.
To remove any remaining surface contaminants, a production line typically includes multiple washing and rinsing baths, as well as ultrasonic cleaning. In order to further remove unwanted moisture and gases from the lens surface, the lenses are then air dried and heated in special ovens.
The lenses are then loaded into special metal racks with spring-loaded openings so the lenses are held securely while virtually exposing the entire lens surface for coating application. A vacuum is created by sealing the door of the coating chamber and pumping air out of it to create a vacuum. The racks are then loaded into the coating chamber.
As the lens racks rotate in the coating chamber, an electron beam is focused on a small crucible containing several metal oxides in separate compartments by a power source within the machine.
As electrons bombard the coating materials, they vaporize within the coating chamber and adhere to the surfaces of the lenses, creating an optical layer that is uniform and microscopically thin.
The AR coating is factory applied to both lens surfaces of some spectacle lenses. Progressive lenses and multifocal lenses (bifocals and trifocals) are typically coated after they have been custom-made by an optical laboratory in accordance with your spectacle prescription.
Choose the AR coating that is right for you
Although each manufacturer of AR coatings has its own proprietary formula, they generally consist of multiple microscopic layers of metallic oxides with alternating high and low indexes of refraction.
Due to the fact that each layer affects a different wavelength of light, the more layers there are, the more reflections will be neutralized. Some AR coatings have as many as seven layers.
You may require an anti-reflective coating that filters out blue light if you spend a lot of time working on a computer.
A slight residual colour, usually green or blue, exists on most lenses with anti-reflective coatings, depending on the AR coating formula.
This multilayer AR coating is generally only 0.2 to 0.3 microns thick, or about 0.02 percent (two one-hundredths of one percent) of the thickness of a standard spectacle lens.
Taking care of anti-reflective lenses on glasses
The anti-reflective coating on AR-coated lenses should only be cleaned with products recommended by your optician. Lens cleaners containing harsh chemicals may damage the coating.
You should not attempt to clean AR-coated lenses with a dry cloth. Using a dry cloth on a dry lens can cause scratches. Furthermore, since antireflective coatings eliminate light reflections that can mask lens surface defects, fine scratches are often more visible on AR-coated lenses than on uncoated lenses.