Ophthalmic Technology Review
For the purpose of this review, the definition of Ophthalmic refers to objects of, relating to, or situated near the eye. The industry of coating ophthalmic lenses includes the following:
- Antireflective Coatings (AR Coatings) - thin layer(s) applied to a lens to reduce surface reflection, which refers to the amount of reflected light and glare that reaches the eye.
- Multi-Layer Stack Coatings - High Index - type of lens with a higher index of refraction, meaning that light travels faster through the lens to reach the eye than with traditional glass or plastic. It is denser, so the same amount of visual correction occurs with less material (whether glass or plastic), and the lens can be thinner.
- UV Protective Coatings - Ultraviolet -the invisible part of the light spectrum whose rays have wavelengths shorter than the violet end of the visible spectrum and longer than X-rays. UVA and UVB light are harmful to your eyes and skin. A lens coated with specific materials can protect the eye and/or skin from hazardous UV radiation.
- Wear Protection/Decorative Coatings - lenses are sometimes coated/tinted to produce a Fashionable color. This typically happens by small amounts of selective metals being introduced to standard AR coatings. This addition occurs during deposition and will produce coloration. Also, wear or Scratch Resistant coatings are utilized to extend product life, therefore enhancing quality.
- Transitional Coatings – Photogrey – lenses that darken to a moderate shade of grey as you go from indoors to outdoors.
Products Used - SFG™, EVAPro™
Ophthalmic coatings consist mainly of transparent oxides and/or fluoride films with different, well-defined refractive indices. Simple AR coatings are generally multi-layers of SiO(2) and TiO(2).
What are Ophthalmic Coatings?
AR coatings reduce reflectance through the process of “optical interference” which counteracts reflected light waves. As a result, reflected light is reduced while light transmission is increased. This is accomplished by a variety of multi-layers of thin film coatings. AR coatings are added to finished lenses to improve vision and appearance. Lenses coated with this process virtually eliminate the reflection from the back of spectacles, such as images of your own eyes and eyelashes.
AR coatings allow more light to reach your eyes, which increases contrast and clarity. This means you actually see better; particularly in low light situations like night driving. Light reflections from the front of your lens are also significantly reduced. This makes the lens almost invisible, making your eyes the focus of attention, not your glasses.
High Index Lenses
High Index Lenses, or “thin” lenses, are typically produced using a plastic lens material. This type of plastic lens dramatically reduces lens thickness and is lightweight. High Index, multi-layer coatings are applied to the plastic lens. High index coatings are also available to be applied to a glass lens, but, results in a considerably heavier lens.
UV coatings help reduce the risk of retinal or skin damage and cataracts as a result of exposure to the sun or fluorescent lighting. Scratch resistant coatings can be added to finished lenses to protect them from damage due to everyday use. Excessive scratching can compromise vision and detract from appearance.
Lens tinting is done for several reasons. Many eyeglass wearers tint their lenses for fashion and comfort. Lenses can be tinted to closely match their fashion frame of choice OR to reduce glare from computer screens, high gloss paper or fluorescent lights.