What's the difference? Knowing your lens type
When purchasing a new pair of frames, sunglasses or eyeglasses, there are a few things to take into consideration. One of the most important is the type of lens you need in your frame. But, do you know the difference between polycarbonate or progressive lenses? What about photocromic vs anti reflective coatings? Exactly. It’s a lot of information but, we’re here to help.
Our in house Optometrist Dr. Henry has provided a quick guide that describes the different lens types and treatments available for lenses. He describes their specific purpose, function, as well as their benefits. Hopefully providing you with more clarity to make the process of getting a new pair of frames easier.
Single Vision Lenses:
A single vision lens has the same power of correction across its whole surface. It can be used to correct “simple” vision conditions, such as myopia (short sightedness), hyperopia (long sightedness) and astigmatism. It can be available in different materials, such as polycarbonate or high-index.
Bifocal Lenses:
Bifocal lenses have a very distinct line dividing a reading area from distant viewing. They are designed to allow you to see objects either near or far by essentially combining two lenses into one.
Progressive Lenses:
Progressive lenses are “multi-focal.” In other words, the progressive lens corrects more than one vision condition, with its focal power “progressing” from top to bottom - without a visible line separating them. Progressive lenses are generally only required as we reach middle age, to correct the blurry, near vision condition called Presbyopia. Progressive addition lenses offer a gradual transition from distance to near vision, while also allowing you to see objects at arm’s length.
Polycarbonate Lenses:
Polycarbonate is lighter and significantly more impact-resistant than CR-39 plastic lenses, making it a preferred material for children's eyewear, safety glasses and sports eyewear.
High-index plastic Lenses:
These lenses are thinner and lighter than normal (CR-39) plastic lenses because they have a higher index of refraction. This lens type is ideal for high prescription lenses. High-index lens material reduced the thickness for greater comfort and a better appearance.
Polarized Lenses:
Polarized lenses filter out horizontal light rays and thus reduce glare to the barest minimum. For anyone who is light sensitive, polarized lenses are recommended especially for people who spend a lot of time outdoors. For instance, if your work involves you working outdoors most of the time when doing high-glare activities, polarized lenses would help. They assist to reduce glare and provide additional clarity while keeping your eyes protected.
Lens Treatments:
A lens treatment is an addition to the lens - it either bonds with the lens, or is built into it during the lens manufacturing process. Here are some typical treatment options for your lens you’ll see when purchasing a pair of frames.
Anti-scratch coating: All lightweight eyeglass lens materials have surfaces that are significantly softer and more prone to scratches and abrasions than glass lenses. The softest eyeglass lens is also the one that is the most impact-resistant: polycarbonate. But all plastic and high-index plastic lenses require a factory-applied anti-scratch coating for adequate lens durability.
Anti-reflective coating: An anti-reflective (AR) coating eliminates reflections in lenses that reduce contrast and clarity, especially at night. They also make your lenses nearly invisible, so you can make better eye contact. That way, you and others aren't distracted by reflections in your lenses. AR-coated lenses are also much less likely to have glare spots in photographs.
UV-blocking treatment: Cumulative exposure to the sun's harmful ultraviolet radiations over a person's lifetime has been associated with age-related eye problems including cataracts and macular degeneration. For this reason, people should protect their eyes from UV beginning in early childhood. Thankfully, polycarbonate and nearly all high-index plastic lenses have 100 percent UV protection built-in, due to absorptive characteristics of the lens material.
Photochromic Treatment: This lens treatment enables eyeglass lenses to darken automatically in response to the sun's UV and high energy visible light rays and then quickly return to clear (or nearly clear) when indoors.
Transition Treatment: Original Transitions lenses are designed to meet the needs of the majority of those who appreciate the value of eyewear offering adaptive lens technology. With the widest variety of lens designs and materials to choose from, original Transitions lenses quickly adapt between indoor and outdoor conditions, offering a distinct advantage over ordinary clear lenses. Transition lenses change from clear indoors to dark outdoors when it’s sunny. They become clear as an ordinary clear lens when indoors and at night and it blocks 100% of the sun's harmful UVA & UVB rays.
Bôhten has an array of frames and lenses available directly on our site. Visit https://bohten.com to order for your lenses.
Written by Optometrist Dr. Henry