This handy quick-reference guide provides breaks down some of the most-common terms associated with lenses. It also provides some information on the types of products available on the market today.

What is it? Blue light, also known as high-energy visible light, is emitted by smartphones, tablets, computer screens and televisions as well as compact fluorescent light bulbs and the sun.
Blue light can cause digital eye strain, which is marked by dry, irritated eyes, headaches and neck and back pain, but research suggests long-term exposure can also lead to long-term issues like age-related macular degeneration and cataracts.
On the market: Many eyewear companies have developed lenses and lens treatments to help protect the eyes from blue light.
HOYA Recharge, for one, is an anti-reflective lens treatment that helps to protect the eyes from damaging blue light wavelengths. All Transitions lenses also help shield the eyes from harmful blue light.

What are they? Photochromic lenses adapt to lighting conditions.
The specialized light-adaptive lenses contain photochromic molecules that cause the lenses to automatically darken when exposed to ultraviolet light. The lenses return to clear while indoors.
On the market: Transitions is the leading manufacturer of photochromic lenses, but other companies, such as Vision Ease, Rodenstock and Centennial Optical also develop and sell self-tinting lenses.

What are they? Polarized sunglasses contain a special filter that helps to reduce glare.
The lenses, which first became available in 1936, are especially popular with outdoor enthusiasts, such as boaters and joggers who often come into contact with intense reflected light from the surface of water or pavement, respectively. However, they are also available in everyday sunglass lenses and can make images more clear and crisp.
On the market: Each pair of sunglasses in the Polaroid Core, Trend, Premium and RX Sunglass collections, distributed by Safilo, feature premium Polaroid UltraSight polarized lenses to ensure perfect vision and protection at its best.

What is it? UV light is a form of electromagnetic radiation that cannot be seen by the human eye. UV rays are emitted by the sun as well as man-made sources, such as light bulbs and tanning beds.
Prolonged exposure to UV rays can cause painful injuries to the eye, according to Health Canada, and can also create long-term problems, such as loss of vision, cataracts and cancer of the eyelid.
On the market: Rodenstock’s ColorMatic IQ Sun 2 self-tinting lenses provide 100% UVA and UVB protection.
What are they? Free-form lenses are a type of high-definition lenses that are created using specialized computer-controlled manufacturing processes.
Free-form lenses are made to more closely match the wearer’s prescription, while also taking into account variations in the person’s eyes across the surface of the lens and how the lenses are positioned in front of the person’s eyes.
The result is a lens that offers improved clarity and better low-light vision, colour and contrast perception.
On the market: Kodak Unique HD progressive lenses, distributed by Centennial Optical, are created using position-of-wear measurements to more highly customize the lens to the individual patient’s viewing needs.

What is it? Anti-reflective coatings are thin layers that are added to a lens to reduce the amount of light reflected off the front of the lenses as well as to cut down on the glare that the wearer sees while wearing the lens.
Anti-reflective coatings can improve vision and reduce eye strain.
On the market: Essilor Multicoated Antireflective coatings resist scratches and smudges, repel water and offer anti-static properties.