Behind the Lens

Lens Types

1. Single Vision
Single vision lenses are the most commonly prescribed lenses on the market. They were developed for people who need to correct one field of vision, either distance or near. They have the same power of correction across its whole surface and can be used to correct conditions such as farsightedness, nearsightedness and/or astigmatism.
Fact – This lens was once used to view gladiator competitions by a Roman Emperor. Over a thousand years later, the first single vision lens was invented to correct astigmatism by an optician in Philadelphia. Before the 1800s, there was no way for someone with astigmatism to see clearly.

2. Bifocal
Includes two different areas of vision correction, which are divided by a distinct line that sits horizontally across the lens. The top portion of the lens is used for distance and the bottom portion of the lens is used for closer vision.
Fact – Benjamin Franklin invented these. Up until the beginning of the 20th century, two separate lenses were cut in half and combined together in the rim of the frame to create bifocal lenses. A little clunky, but they did the trick. Today, most bifocals are created by using an optical mold to create a reading segment within a primary lens.

3. Progressive/No-Line Bifocals
These lenses are a perfect marriage of form and function. With no lines across the lens others won’t even know you’re wearing a multi-focal lens. They provide a graduated range of vision that varies from distant on the top to reading on the bottom. Along with the cosmetic appeal, this is the best lens for complete vision correction at all distances.
Fact – Invented in 1959 and technology has advanced through the 80s, 90s and 00s. Today, there is a wide assortment of progressive lenses offered by a large number of lens manufacturers.

Enhancements

1. Polarized
These are used in sunglasses to eliminate the sun’s glare and help you see more comfortably. These lenses eliminate distracting reflected light from reaching your eyes. That means there’s less glare off of shiny surfaces like pavement and water. They offer 100% UV protection, reduce squinting and eyestrain and may help fight eye fatigue and headaches.
Best for: Sun protection is crucial for all patients of all ages and should be worn by everyone when outside. Polarized lens are available in sun photo chromatic lenses. They’re especially recommended for patients with eye conditions such as cataracts and age-related macular degeneration and are ideal for eliminating glare off of water and snow.
Fact – Sunglasses were first worn by pilots to help them combat the sun’s glare.

2. Anti-reflective
AR coatings eliminate the reflection in lenses that reduce contrast and clarity. They improve night vision while also reducing headaches, blurred vision and watery eyes caused by eye strain. They also make your lenses nearly invisible, so you can make better eye contact and you and others aren’t distracted by the reflections in your lenses.
Best for: AR coating is always a good addition to any lens material. It’s also helpful for those who drive a lot in the dark and work often on a computer.

3. Digital/HD lenses
These are digitally made for accuracy and designed to provide sharper vision, improved peripheral vision and increased clarity so colours appear more defined and details more vivid. Often these lenses require additional measurements to personalise the lens for you.
Best for: Those with a complex prescription or progressive lens wearers will notice the greatest improvement from digital lenses.
Fact – Recent advances in lens manufacturing makes digital lenses possible, but because of the sophisticated technology used to design and fabricate them, plus the added time and equipment required to fit them, they’ll likely cost you a bit more than conventional lenses.

4. Blue Light
The artificial light from digital devices, also known as blue light, may cause blurry vision, difficulty focusing, dry and irritated eyes, headaches and even macular degeneration. To help combat the effects, blue light protection may either be incorporated into the lens material itself, or it may be added to a lens as a finishing coat. These special lens treatments provide protection from harmful high-energy blue light.
Best for: Anyone who spends hours in front of a computer/tablet or phone.
Facts – The effects of artificial blue light are so new that we’re still trying to understand what options are best and how they may help vision long-term.

5. Photo Chromatic
Have you ever noticed that some people have glasses that change from dark to light just by walking indoors? They’re probably wearing photochromic lenses (also referred to as variable tint, Transitions® and light adaptive lenses). These lenses continuously adapt to changing light conditions and are virtually clear indoors and at night. Plus, they also block UV rays.
Best for: Anyone who wants the convenience of one pair of glasses that adapts to light and dark. But here’s a tip—car windshields block the UV rays that make it possible to darken so if you spend a lot of time in the car make sure you have a pair of polarised shades on hand.
Fact – Molecules take centre stage in these lenses. When exposed to UV rays in direct sunlight, they undergo a chemical process that causes them to change shape and absorb a significant amount of the visible light (aka they darken). The process is reversible, meaning once the lens is removed from strong sources of UV rays the photo chromatic compounds return to their transparent state.

Materials

1. Plastic
Introduced in 1947, these have become the most economical and commonly used material for eyeglass lenses. They’re more lightweight and thinner than glass lenses.
Best for: Value conscious consumers
Fact – These lenses were made of a plastic polymer called CR-39® in the early 1940s. It was the first plastic suitable for eyeglass lens production. Decades later, in the 1980s, a plastic material with a higher refractive index emerged. Today, modern technology continues to advance plastic lenses to make them thinner and lighter.

2. High Impact
This super thin lens is more lightweight than polycarbonate and is best for those with a strong prescription. They bend light more efficiently, meaning light travels faster through these lenses than traditional lenses. High-index lenses can offer the same degree of visual correction using less material, which results in thinner lenses and less weight to your glasses.
Best for: People with a strong prescription who want a lighter, thinner look.
Fact – The latest lens material was developed to eliminate the “Coke-bottle” effect associated with thicker, conventional lenses. Hi-index lenses are typically referred to by their refractive index. As the index increases, the lens can become thinner.

3. Polycarbonate
This impact and scratch resistant, durable lens is thinner and lighter than plastic and provides 99% UV protection. But here’s a tip—they can scratch, so make sure to ask for a scratch protection coating to help.
Best for: Anyone with an active, sporty lifestyle, especially children.
Fact – The material was originally created for the cockpits of fighter planes, and since then, it’s been used to make the visors on astronaut helmets and the windshields of space shuttles. Today, polycarbonate is the most-used alternative material for eyeglass lenses.

Behind a glasses lens

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