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Types of Lenses
Choosing frames is the fun part, but your lenses are the most important factor in clear comfortable vision.
- Lens Type – single vision, anti-fatigue, office, progressives, transitions, polarized and many more.
- Material, index and surfacing – these determine the level of optical distortion and lens thickness
- Coatings – these determine the level of glare, UV protection, blue-light filtering, scratch resistance, ease of cleaning and much more
Making sense of it all is our job. We will help you choose lenses best suited to your lifestyle, budget and and vision needs. Read on for more information on lens designs and options
This is the most simple type of lens, providing clear vision at a single focal distance. For most people, these lenses are made for either far, computer, or reading viewing distance. We can categorize these lenses into 2 types:
These lenses are the least expensive since they are mass produced in a variety of common powers. However, when your eyes are not looking through the optical centre, the vision can get distorted or blurry. The amount of blur is dependent on the distance from the eye to the lens, the curvature (wrap) of the frame, as well as the lens power.
For ideal vision with these lenses, they must be centered precisely to your pupils, in a well fitting frame that does not sit far from the eyes. Proper centration requires 2 measurements, monocular PD and OC height (see below for what these are). Without these measurements, centration is impossible. Because online eyewear purchases cannot take into account where your pupil sits in the frame, the only measurement they can use is the horizontal distance between your eyes (PD), not enough to properly center the lens, often leading to eye strain and blur when looking off center.
These lenses provide superior vision from edge to edge with minimal to no distortion. They also look better as they are up to 16% thinner and 49% flatter than conventional lenses when ideally fitted. A proper fitting involves the following measurements:
- Monocular PD – the distance from the centre of your nose to the centre of the pupil on each side
- OC height – the vertical distance from the bottom of the frame to your pupil
- Frame wrap – the curvature of the frame
- Pantoscopic tilt – the tilt angle of the bottom of your frame relative to the front plane of the face
- Vertex distance – the distance from the back of the lens to the front of your eye
These days, we are using our eyes up close more than for distance, resulting in a huge amount of stress on our focusing muscles. This leads to eye strain, fatigue and dry eyes from reduced blinking.
An anti-fatigue lens has a “near activated zone” in the bottom with an adjusted focal power suited for viewing digital devices at near. This helps reduce the strain on the focusing system leading to less fatigue and more comfortable vision. Accurate measurements are critical to ensure proper placement of this near zone.
Progressive lenses are clear for distance and have increased reading power the further down you look in the lens. As with all lenses, accurate measurements are essential for correct placement of your distance, intermediate and reading zones. If not done properly, you will have a very narrow field of clear vision find yourself “hunting” for a clear image.
The lens design choice is based on how you use your eyes every day. Every progressive is different in the size of zone and the power transition. In general higher end lenses will have less side blur because the prescription is controlled for points further from the centre. There are also newer designs that equalize the magnification difference between lenses, and others that take into account how your eyes move when you read.
Office lenses are the ideal solution for computer users. They are designed to allow clear computer viewing without tilting your head. This is because the focal point in the centre of the lens is at your computer distance. Above this point there is slightly less power to allow you to see a few metres across a room, and below this point is added reading power to allow you to read items up close and see your keyboard clearly.
These variable near focus lenses have minimal side blur and allow wider fields of view than progressives. They can be customized for a slightly farther distance for those that need to see clients or get up from their desks more often, but are not suitable for driving or far distance viewing.
We generally advise a blue light coating on these lenses which further reduces the eye strain. Since blue light is the most out of focus wavelength, eliminating or reducing the amount of this light will allow for clearer and more accurate focus.
Almost all lenses nowadays have anti-glare coatings but they are NOT created equal.
Conventional single vision lenses come pre-coated from the factory. These coatings can vary in quality, which is often price dependent. Lower end lenses have few layers of anti-glare and poor scratch resistance. Since each layer is specific for eliminating glare of a certain wavelength, more layers means better glare reduction. Good quality anti-glare coatings will transmit over 99.5% of visible light!
Better lenses also have oil-resistant, water-resistant and anti-static coatings to make them easier to clean. To test if your lenses have these higher end coatings, put a sticky note on them and see if it sticks (it shouldn’t)! They should also bead up when you try to write on them with marker.
Blue light coatings
These lenses are designed to reflect (filter) short wavelength blue light from LED devices. Here are some reasons to consider these coatings:
- Blue light affects your circadian rhythm. When you look at digital devices, especially towards bedtime, the body wants to stay awake as if it were daytime. Blocking this light may improve sleep after some late night phone surfing!
- Blue light is the most out of focus wavelength as it focuses in front of the retina. Blocking this light reduces the blur so that images are sharper, the eyes stay more relaxed, and the blink rate improves. This helps to reduce dry eyes.
These lenses are designed specifically for glare reduction and enhanced contrast when driving. They have an coating specifically tuned to substantially reduce glare from modern LED and HID headlights as well as street light glare and light scatter from rain and fog. They also have a filter to enhance low light contrast and brighten up the vision at dawn and dusk.
We are proud to carry both Hoya EnRoute™ and Zeiss Drivesafe™ lenses to ensure your safety and vision comfort while driving. Offered in both single vision and progressive lens designs.
Transitions and Polarized Lenses
Transitions™ or photochromic films turn dark in response to UV or short wavelength light. They darken quickly and provide 100% UV protection, but take a minute or two to go clear. They are great for outdoors but do not get as dark when driving as a true sunglass because there is a minimal amount of UV getting through a windshield.
Polarized lenses are true sunglasses designed to reduce reflected light from horizontal surfaces in addition to just reducing brightness. There are also color enhancing and contrast filters available even better glare reduction depending on what you are using them for. Ask about solid or gradient tints specific for driving, golfing, fishing, water and winter sports.
Accurate Measurements Matter
While online retailers make you take your own “PD” with a ruler, we use the latest high tech digital measurement devices. Simply put, more precise measurements mean better optics, and therefore better vision. This modern tech is similar to motion capture technology used in the movie industry to create realistic animations. By adapting this technology to measuring the way your eyes sit and move in your frame, we can give you quality optics and the clearest and most comfortable vision possible.
This tech, combined with the expert knowledge of your optical consultant at Mission Eye Care will ensure you are looking and seeing to your fullest potential. Click here read our warranty.