Which Eyeglass Lenses should I Choose?

Choosing frames is the fun part, but your lens design is the most important factor in ensuring your glasses will give you the vision you need for the tasks you need them for. Lens design refers to the characteristics of the lens including:

  • Lens Type – single vision, anti-fatigue, office, progressives, bifocals, polarized and many more. All of these lenses have pros and cons depending on the tasks they are used for
  • Material, index and surfacing – these determine the optical quality (level of 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 the job of a good optical dispenser. They are trained to dive deep into your lifestyle and vision needs to give you the best recommendation on the products most suited to your needs. Read on for more information on the various lens options available!

Single Vision

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:

Conventional lenses

These lenses tend to be inexpensive since they are mass produced in a variety of powers. The drawback is that they only have your correct prescription in the centre of the lens. 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.

Digital lenses

These lenses provide superior vision because they are custom made to account for the optics of how the eyes move relative to the lenses. The complex calculations take into account 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 measurements can only be taken once you have selected a frame and it is properly adjusted on your face. Because they provide correct optics across the ENTIRE lens, they give you superior clarity from edge to edge.

Anti-fatigue

This type of lens came to market a few years ago to address the problem of digital eye strain. Our eyes were designed by nature to suit our “hunter-gatherer” ancestors. They used their eyes to hunt at distance, and pick the occasional berries up close. 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. The same set of measurements that apply to digital lenses ensures proper placement of this near zone.

Progressives

Progressive lenses are designed to have increased reading power the further down you look in the lens. In addition to the measurements for digital lenses described above, we also need to know how much your eyes turn inwards for near viewing. This is known as your “near PD” and measuring this accurately ensures correct placement of your reading corridor. If this is not done properly, you will have a very narrow field of clear vision find yourself “hunting” for a clear image.

These lenses are the most confusing for the consumer since there are over 800 designs of progressive lens! Each one is unique in how the power transitions from distance to near. Those with higher distance demands prefer the reading area lower down, those who read a lot prefer it higher up. Some lenses are designed with wider distance and reading zones but have a very narrow computer zone, others have wide computer viewing zones but more side blur at distance. There is no perfect progressive, the design choice is based on what you need the most. For those that need very wide reading areas and don’t mind a line, there are always traditional bifocals.

Higher end progressives will have less side blur because the prescription is controlled for points further from the corridor. These digital progressives take the frame fitting characteristics into account just like the digital single vision lenses described above to provide a truly customized lens for optimal vision. There are also designs that equalize the magnification difference between lenses, this is especially important if your prescription is quite different between eyes.

Office Lenses

Because progressives have a relatively narrow near focal zone located lower down in the lens, they are not ideal for long term use on a computer. A progressive lens user has to tilt their chin up and do a lot of head turning to find the “sweet spot” for computer viewing. This leads to eye strain and are literally a pain in the neck!

Office lenses allow clear computer viewing without tilting your head. They are designed so 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.

Coatings

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. The more layers, the better the glare reduction since each layer is specific for eliminating glare of a certain wavelength. 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, but we don’t want you to try this at home.

Blue light coatings

These lenses have a blue tinge to them since they are designed to reflect (filter) short wavelength blue light from LED devices. There is some evidence that long term exposure to this light at close distance can cause damage to the retina and lens, albeit much slower than that from UV exposure. There are some other reasons to consider these coatings:

  1. 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. By blocking this light, you may have an easier time going to sleep after some late night phone surfing!
  2. Blue light is the most out of focus wavelength. Because it focuses in front of the retina, the eyes will often strain to get it into focus. By blocking this light, the images are sharper and the eyes stay more relaxed and blink normally. This can also help with dry eyes

DriveSafe Lenses

This is a type of lens designed specifically for night and low-light driving to reduce glare. They have an anti-glare 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 very faint yellow tint to enhance low light contrast and brighten up the vision at dawn and dusk. These lenses have a blue tinge similar to blue light coatings.

Transitions and Polarized Lenses

These are not coatings but they are materials embedded in your lens. Transitions or photochromic films are designed to turn dark in response to UV or short wavelength light. Good quality photochromics darken quickly and provide 100% UV protection, as well as turn clear more quickly than older type films.

Polarized sunglass lenses are designed to reduce reflected light from horizontal surfaces. Some manufacturers use dual layer polarization for even better glare reduction. These provide the best clarity and glare reduction for driving, golfing, fishing, water and winter sports.

Accurate Measurements Matter!

High Tech = Better lenses

We use the latest high tech digital measurement devices to precisely calculate distance and near monocular PD, OC, wrap, tilt, and vertex distance. 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 the most precise and custom optics available.

This tech, combined with the expert knowledge of  your optical consultant at Mission Eye Care will ensure  your lenses give you the best vision possible for your unique visual demands.

Our Warranty

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*Exceptions – 90 day warranty on clearance frames, 1 yr warranty on non-premium (value package) lenses, cleaning solution refill includes our original bottle only