Doig Optometry is Your Place for Progressive Lenses

Doig Optometry is Your Place for Progressive Lenses

Progressive Lens Wearers Experience Common Problems

If you need progressive lenses, you have one prescription at the top of your glasses and a different prescription at the bottom. This difference is what allows us to see well at both far and near distances, but it’s also the cause of a common set of problems among progressive lens wearers. “Swim” and “Sway” are two common words patients use to describe the funny way their progressive lenses make the world look when they move about.  

What Causes These “Swim and Sway” Problems?

It’s all about magnification. Specifically, “Swim and Sway” are the result of differences in magnification as the eyes move from one area of the eyeglasses to another. These differences in magnification are even more problematic if your prescription is different from one eye to the other.

How Can We Eliminate “Swim and Sway”?

Hi, I’m Doctor Doig and I’m passionate about progressive lenses. I consider ten variables after we determine your prescription. Each of these ten variables can have a positive or a negative impact on your progressive lens experience. It’s my job to thoroughly understand each of these ten variables. From there, I can design a progressive lens that’s customized for your eyes, so your progressive lenses just work. With minimal or even no experience of “Swim or Sway”, you’ll be able to wear them with no frustrating adaptation period.  

If you need progressive lenses, I’d love to help you make your next pair of progressive eyeglasses the best they can be. If you’d like to talk about progressive lenses and what they can do for you, contact me at 403-333-3353 and info@doigoptometry.com
.
Updated:

Posted in: Blog

Magnification in Progressive Lenses – The Root Cause of Adaptation Issues

I graduated from Optometry School in 1996, and in the years that have passed since then I’ve heard many patients say something like, “I’ve tried progressive lenses, but I couldn’t get used to them.” In more recent years, I’ve heard more and more patients say, as one did earlier this year, “Thank you Dr. Doig. That’s the first pair of progressive lenses that I didn’t have to get used to.”

The process of getting used to a pair of progressive lenses is called “adaptation”.  Thankfully, today’s progressive lens wearers live in the era of computer assisted lens design. Thanks to computers, we can design your progressive lenses specifically to minimize or even eliminate your progressive lens adaptation experience altogether. Providing my patients with the best progressive lens adaptation experience requires understanding the variables that contribute to each patient’s unique adaptation experience, and then customizing their progressive lenses specifically for their eyes.  In fact, the desire to give you the very best possible progressive lens experience was one of my prime motivations for opening my Calgary Optometry Clinic, Doig Optometry.

The longer I practice optometry, and the more I study progressive lens design, the more I’m convinced that magnification effects determine the patient’s adaptation experience. Specifically, adaptation problems are due to a difference in magnification in the upper (distance) viewing zone of the progressive lens, and the magnification in the lower (reading) zone. 

To skip the following technical explanation, click here.

Spectacle lens magnification is a product of two variables: the power of the spectacle lens, and the shape of the lens.

Spectacle Lens     =    Shape     X     Power
Magnification              Factor           Factor

The shape factor is the magnification that results from the shape of the front of the lens.  We call it F1 in the following formula:

Shape     =             1         
Factor             1 – (t/n) F1  

There are two other things that can increase or decrease the magnification that comes from the shape factor. The thickness of the lens (t in the formula above), and the index of refraction of the lens material (n in the formula above). Index of refraction is a measure of how well the lens material bends light. If the material bends light really well, it allows for greater control over thickness and the shape of the front of the lens. 

The power factor is the magnification that results from the power of a prescription lens.  The power of a spectacle lens can be measured at the front surface of the lens, or at the back surface of the lens (F’v in the formula below). The power of a prescription lens can also be measured at a certain distance from the lens. These three measurements will all be different. The important point here is that the magnification due to the prescription power of a spectacle lens will vary at different distances from the lens. In other words, as your progressive lenses move closer or further from your eyes, the size of the image you see will change. The change will be larger or smaller depending on your prescription. That’s why we measure the distance between your eyes and your glasses at my Calgary Eye Clinic, Doig Optometry. This distance is called “the vertex distance” (v in the formula below).

Power      =           1       
Factor               1 – v F’v  

The take-home message from all this math can be summarized this way:

The front of a progressive lens creates magnification due to its shape and thickness.  The back of a progressive lens creates magnification due to its power and its distance from the eyes.  

Prior to 2008, when every progressive lens was manufactured in a similar, conventional way, the reading prescription was always on the front and the patient’s distance prescription was on the back of the lens. This had a huge impact on the magnification profile of these conventional progressive lenses because:
  1. The front of a progressive lens creates magnification due to its shape, and the front of a conventional progressive lens is shaped differently at the bottom compared to the top.
  2. The front of a progressive lens creates magnification due to its thickness, and the bottom of a conventional progressive lens is thicker than the top.
  3. The back of a progressive lens creates magnification due to its power, and the bottom of a conventional progressive lens has a different power than the top.
  4. The back of a progressive lens creates magnification due to its distance from the eyes, and the bottom of a progressive lens is further from the eyes than the top.

Thankfully, a critical breakthrough in spectacle lens manufacturing occurred in 2008 and 2009 that allowed us to move the reading prescription from the front surface of the progressive lens to the back.  This single change in the manufacturing process very nearly eliminates all the magnification differences that occur at the front surface of the progressive lens because the shape of the front surface is the same from top to bottom. Also, moving the reading prescription to the back of the progressive lens decreases the magnification differences at the bottom of the progressive lens simply because it’s closer to the eyes. This means that it’s now possible for your eyes to have a more similar magnification experience when they move from the top to the bottom of your progressive lenses.  This is why today’s free-form progressive lenses (when properly designed and manufactured) are much easier to adapt to than yesterday’s older, conventional progressive lenses.

If you need progressive lenses that are easy to use, the eye doctors and staff at Calgary’s Doig Optometry would love to create a customized progressive lens design, specifically for your eyes.  If you’d like us to, we’d love to minimize, or even eliminate any frustrating adaptation period in your new progressive lenses. So please call our Calgary Eye Care Centre, Doig Optometry to book your next eye appointment. See you soon!

Note:  This blog was is for informational purposes only. It was written with the goal of making the complex issue of progressive lens adaptation more understandable for progressive lens wearers.  In order to achieve this goal, certain optical and mathematical concepts were simplified in order to make them more understandable. If you were able to identify them, congratulations! You are on your way to becoming a masterful expert of optics. If you have any questions or insights about the management of magnification in progressive lens design, I welcome your comments. You can reach me via the contact page on this website, or by email at info@doigoptometry.com.

Thanks!  
– Dr. Doig

.
Updated:

Posted in: Blog

Understanding Progressive Lenses

Choosing the right lens for your glasses is a lot easier when you know a thing or two about your options. Progressive lenses are our specialty at Doig Optometry, so it’s only right that we get you acquainted with how this particular lens works and why it might be right for you.


The Basics


Like other corrective lens types, progressive lenses are designed to correct refractive errors that disrupt the eye’s ability to focus light. One of the most important factors in compensating for these issues is lens power. Single vision prescriptions offer a uniform lens power throughout the lens, and bifocal or trifocal lenses offer multiple lens powers that are sharply divided from one another. Progressives, however, provide a continuous range of lens power that increases gradually from the minimum power of your prescription at the top of the lens to maximum power at the bottom, bringing close objects sharply into focus.


Correcting Presbyopia


Most people experience one or more refraction errors, such as nearsightedness, farsightedness, astigmatism, or presbyopia. For those above the age of 35, presbyopia is particularly common and is a natural result of the eye aging. Over time, the lens of the eye loses elasticity and cannot properly refract incoming light, focusing it behind the retina rather than onto it. This results in difficulty focusing on near objects as well as eye strain or headaches. Progressive lenses correct this issue in a way that mimics the eye’s natural accomodation to distance, and they’re particularly handy if you experience presbyopia in addition to other errors.


Progressive Lens Sunglasses


The central reason why so many people choose progressive lenses is their convenience and versatility. They do what bifocals and trifocals do, only more smoothly and dynamically. Not only this, but when you need sunglasses made from your prescription, you’ll be able to stay active and enjoy the outdoors with a great-looking pair that is free of unsightly lines. No one should be unfairly limited by stylistic or lifestyle factors when choosing their glasses, and the same should go for sunglasses as well. Whether you’re indoors or in the sun, if you want to see clearly and maintain a youthful and modern look, progressive lenses are an excellent solution.


Dr. Doig and Dr. Chorel are natural born problem-solvers, dedicated to finding the right lenses and eyewear based on the unique needs of each and every patient. From comprehensive eye exams to glasses, sunglasses and beyond, call us at (403) 333-3353 and we’ll be happy to help
.
Updated:

Posted in: Blog

Ultraviolet Light is High Energy Light

Calgary is the sunniest of all the major cities in Canada. Over half of Calgary’s total daylight hours (2396 on average per year) are hours of sunshine. Since that sun is spread out over 333 days per year (more than any other city in Alberta) there’s a lot of opportunity for us to get outside and enjoy Calgary’s sunshine in the summer and throughout the winter. When we are outside, it’s important to protect our eyes, and not just our skin, from UV light by wearing glasses with UV blocking.  

Ultraviolet (or UV) light is invisible, but it carries a high amount of energy. So much energy, in fact, that it can cause a sunburn. Did you know that the same UV light energy that causes sunburns can also damage the eyes?  

When our eyes are exposed to the bright Calgary sunshine, they feel the energy contained in the UV light and become sensitive. Photosensitivity, or light sensitivity, makes us feel as though we want to close our eyes or shade them from all that extra light energy. We naturally reach for dark sunglasses when our eyes feel this way. Dark colours help, but for your sunglasses to decrease your light sensitivity, they must eliminate your exposure to UV light. Thankfully, UV blocking coatings and materials are available for both prescription and non-prescription sunglasses.  

UV blocking coatings and materials have greatly improved over time. In Dr. Doig’s opinion, “UV blocking lenses are better now at blocking ultraviolet light and they are much clearer. When I started my career in eyecare, there was a yellow tinge to all lenses that blocked ultraviolet light. That’s why such lenses weren’t used much in our clear prescription glasses.”  In the past, UV blocking materials were more commonly used only in sunglasses, where the yellow tinge didn’t matter. There would be a dark tint added over the UV block anyway, hiding the yellow tinge. Today, UV blocking coatings and materials can be so clear that one major lens supplier now includes their UV block on all their prescription and non-prescription lenses as a basic feature. Dr. Chorel and Dr. Doig are very excited about this recent news (May 2018).

“As your eye doctor, I’m most concerned that your sunglasses protect you against damage that can come from UV light in the form of cataracts, macular degeneration and even cancer of the eye,” says Dr. Doig. That’s why all the sunglasses sold at Doig Optometry are UV blocking. “That’s also why contact lens users should wear UV blocking sunglasses. Even contact lenses that block UV light don’t provide protection for the conjunctiva (the white of the eye), the eyelids, or the skin around the eyes.” These are obviously places where we don’t put sunscreen.  

Dr. Doig makes one other recommendation when it comes to UV light: “Since UV light from behind you is reflected off the surface of your sunglasses and back towards your eyes, it’s a good idea to put an anti-reflective coating on the back side of your sunglass lenses.”  That way, the UV light coming from behind you will absorbed by your UV blocking lenses without reflection.

Do you have the right lenses to protect you from the UV light in our bright Calgary sunshine? Doig Optometry provides UV blocking clear eyeglasses and UV blocking sunglasses with or without prescription. To learn more about our sunglass brands and to book an appointment, please call us at 403-333-3353 today
.
Updated:

Posted in: Blog

Fashion Sunglasses Need UV Protection

Did you know that Calgary is the sunniest of all the major cities in Canada? Calgarians experience an average of 2,396 hours of bright sunshine per year. That’s over half of Calgary’s total daylight hours every year. Those hours of sunshine are spread out over 333 days per year, which is the most days of sunshine for any city in Alberta. No wonder we love to live in Calgary! Of course, this means you need to ensure that your sunglasses come with UV protection.

We’ve been taught to take care of our skin when we’re out in the bright summer sunshine and it’s important to think about protecting our eyes too. It doesn’t matter whether we are outside enjoying the bright Calgary sunshine in the summer or in the winter, our eyewear should protect us—but from what? Uncomfortable light sensitivity, distracting glare, and harmful ultraviolet light are the three main culprits.  

When it comes to our vision, we all feel more sensitivity to sunlight on a bright sunny day than we do on a grey, overcast day. Choosing a dark pair of sunglass lenses will help make patients more comfortable in the bright Calgary sunshine, and the colour chosen is what dictates the fashion of our sunglass lenses. In terms of comfort and vision, a neutral grey lens colour is the most natural because it decreases the brightness of all colours equally. Since it doesn’t shift your perception of colour, it’s the most popular colour for sunglasses. If you need to shift the colour to make something easier to see, such as the golf ball on the course, or when you are skeet shooting, ask Dr. Doig and Dr. Chorel at your next exam which colour will be the most helpful. Otherwise, choose the colour that best suits your style and your fashion!

In the eyecare industry, basic coloured lenses are called “Fashion Tints”.  It’s important to think of fashion tints as just that, because they really don’t offer protection from harmful UV light and distracting glare.  In fact, because the darker tint will allow the pupil to dilate slightly, fashion tints will actually allow more harmful UV radiation enter into they eye.  That’s why laws and regulations require manufacturers to include UV protection in all non-prescription sunglasses sold in Canada. Just remember that this is not a requirement everywhere in the world, so be careful about purchasing sunglasses at the swap meet on your sunny holiday away from Canada.

At Calgary’s Doig Optometry, we ensure that all the sunglasses we sell include UV protection for your eyes. This is true of all the prescription and non-prescription sunglasses we provide to our patients. To read more about the importance of UV protection for your eyes, click here.  To learn more about our sunglasses brands and to book an appointment, please call us at 403-333-3353 today!
.
Updated:

Posted in: Blog

Letter Reversals in Children

Did you know that Calgary is the sunniest of all the major cities in Canada? Calgarians experience an average of 2,396 hours of bright sunshine per year. That’s over half of Calgary’s total daylight hours every year. Those hours of sunshine are spread out over 333 days per year, which is the most days of sunshine for any city in Alberta. No wonder we love to live in Calgary! Of course, this means you need to ensure that your sunglasses come with UV protection.

We’ve been taught to take care of our skin when we’re out in the bright summer sunshine and it’s important to think about protecting our eyes too. It doesn’t matter whether we are outside enjoying the bright Calgary sunshine in the summer or in the winter, our eyewear should protect us—but from what? Uncomfortable light sensitivity, distracting glare, and harmful ultraviolet light are the three main culprits.  

When it comes to our vision, we all feel more sensitivity to sunlight on a bright sunny day than we do on a grey, overcast day. Choosing a dark pair of sunglass lenses will help make patients more comfortable in the bright Calgary sunshine, and the colour chosen is what dictates the fashion of our sunglass lenses. In terms of comfort and vision, a neutral grey lens colour is the most natural because it decreases the brightness of all colours equally. Since it doesn’t shift your perception of colour, it’s the most popular colour for sunglasses. If you need to shift the colour to make something easier to see, such as the golf ball on the course, or when you are skeet shooting, ask Dr. Doig and Dr. Chorel at your next exam which colour will be the most helpful. Otherwise, choose the colour that best suits your style and your fashion!

In the eyecare industry, basic coloured lenses are called “Fashion Tints”.  It’s important to think of fashion tints as just that, because they really don’t offer protection from harmful UV light and distracting glare.  In fact, because the darker tint will allow the pupil to dilate slightly, fashion tints will actually allow more harmful UV radiation enter into they eye.  That’s why laws and regulations require manufacturers to include UV protection in all non-prescription sunglasses sold in Canada. Just remember that this is not a requirement everywhere in the world, so be careful about purchasing sunglasses at the swap meet on your sunny holiday away from Canada.

At Calgary’s Doig Optometry, we ensure that all the sunglasses we sell include UV protection for your eyes. This is true of all the prescription and non-prescription sunglasses we provide to our patients. To read more about the importance of UV protection for your eyes, click here.  To learn more about our sunglasses brands and to book an appointment, please call us at 403-333-3353 today!
.
Updated:

Posted in: Blog
© 2020 Doig Optometry All Rights Reserved.