3D Glasses. How Do They Work Anyway?

My recent piece, describing the difference between polarized and tinted sunglasses inspired me to address 3D glasses, since they also use polarization to work. Yes, you read that right. The same polarizing technology which reduces glare when you’re driving, also allows you to see an extra dimension at the movie theater.

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As you might recall, in my last post on sunglasses, polarized glasses work by having a film sandwiched inside the lens which only allows wavelengths of light to pass through on one plane. 3D movie glasses are using a polarizing film (with no corrective lens around it, and that’s why they are so thin), but their film is doing something quite different. RealD is the most commonly used three dimensional movie projection system. And they use a circular polarizing film. So, in other words, instead of letting light through on a plane, it’s letting it through on a circle. This allows them to “wink” the image constantly between the two eyes, and not cause shear, or blurriness as you move your head around to get your drink, or eat your popcorn.

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ISSUES WITH 3D

In order to keep costs for the 3D glasses at a minimum, theaters use the polarizing film mounted into a frame, with no ophthalmic quality lens holding it in place. This impacts your vision in a couple of significant ways.

  • First, with no lens to keep the film rigid, there can be waviness or lack of crispness to your viewing experience
  • Secondly, the lenses scratch very easily, so not only are viewing through a lens with poor optical quality, but there are scratches in your way as well.
  • Additionally, if you wear corrective glasses yourself, and put the 3D glasses over them, you can have trouble with comfort on your nose, or even looking through the right part of the lens.
  • Lastly, since these lenses are made as inexpensively as possible, they are very hard to keep clean and the fingerprints can create additional blurriness impeding your experience.

There are solutions for most of these issues for a relatively low cost. There are RealD compatible clip-ons and standard glasses available for purchase from your local optician, or even from online retailers (just do your homework here to make sure you’re getting good quality). Of course, as all of you know, I wear glasses almost exclusively and while I absolutely love going to the movies I have not enjoyed 3D experiences for all of the above reasons. Also, the polar film paired with the less bright projection of a 3D film makes everything dim and washed out. But I found a supplier for these 3D clip-ons and they revolutionized my film going experience. The optical clarity is much better, since the lenses are ophthalmic. Also, the tint of the polarizing film is lighter, so the screen is brighter. No scratches means I can see what I’m watching and there is no additional weight on my nose.

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Excellent clarity with 3D clip-ons

TROUBLES WITH 3D?

There is a segment who cannot view a 3D film without terrible headaches and sometimes even nausea. Because the image is flickering at an incredible rate to alternate the images between the two eyes, this flicker can cause serious problems for those susceptible to migraines. Just as there are clip-ons for 3D, there are also 3D for converting your experience to 2D. Essentially it makes sure that both eyes are getting the same single image. I have found these for RealD at Amazon.

What About IMAX?

IMAX uses a completely different technology and I have yet to find solutions for all of these situations for them. But since my favorite movie theatre, where I do my charity work is IMAX 3D I am working diligently to find solutions!

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What are Polarized Sunglasses?

I have found throughout my many years in this industry that many patients still do not have a clear understanding of the difference between a tinted and a polarized sunglass. So, the big question you’re probably asking yourself is, “why do I want over another?”
For the vasty majority of patients, the polarized makes more sense. I hope to explain why here.

Tinted Vs. Polarized – Why one over the other?

The two ways a sunglass lens can be created are vastly different. Tinting is perhaps a bit more straight forward and easier to understand, so I’ll address this first.

When tinting a lens, we start with a perfectly clear lens, and dip it into a hot dye until we get to the color, density, and pattern you desire. The advantage on a tinted lens is that it can be as dark or as light as you’d like. It can be gradient or solid, and it can be pretty much any color under the rainbow (including having mixes of color).

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Gradient Tinted lenses

Based on the above, it sounds like a tinted sun lens is the smartest way to approach it, right? I mean, why discuss anything else??

But what does tinting do for glare? That is the question…and that question is answered with polarized lenses.

Polarized lenses are created in a completely different fashion. There is actually a film sandwiched inside the clear lens (for most versions of polarized…see Maui Jim below). This film is actually made of thousands of microscopic lines packed so closely together they give the appearance of color. These lines are placed so closely together to handle the glare.

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microscopic lines in a polarizing film removed out-of-phase wavelengths of light

How Polarized Works

Polarized lens technology takes advantage of the wave nature of light. When light reaches us from the sun, it folows a unifom wave pattern, wherein all the light is in phase–that is to say all the wavelengths of light are in the same plane. When the light hits a surface, it scatters in multiples angles, creating the flare of glare.  This is where the polarized film in your sunglasses comes in.  All those lines, packed so tightly together, prevent all the scattered light from passing through the lens.  Only the original wavelengths, continuing in their original straight path, are let through.  This dramatically reduced the reflected glare and increases visual comfort, even on a lens with less tint.

Sounds great right?  You must be asking yourself, “Whats the catch?” Well, I wouldn’t call it a catch, but there are a couple of things to be aware of with polarized lenses.  LCD displays use polarized film to work.  When two polarizing films are set 90 degrees apart, all visibility is blacked out.  So this means, if you look at a digital calculator, as an example, it could be black and impossible to see any image displayed.  This is rare, and can be fixed by tilting your head slightly.  In my experience, there can be issues with clarity on the LCD displays for some cars (i.e. BMW’s from the early 2000’s).  This can include your odometer or even your GPS navigation system.  Pretty much all smart phones post version 5 (iPhone, Galaxy) this is a non issue.  But the older devices can have a soap bubble appearance.

Is Polarized Right for You?

For the vast majority of patients, Polarized lenses will be more comfortable and functional. But there are some lifestyles, and work environments where polarized lenses don’t make a lot of sense.

  • Pilots: you’d think this was a perfect case for polarized making sense, but the Shatter resistant windscreens of planes can create tremendous rainbow distortions which are only clearly visible when looking through a polarized lens.
  • Photographers:  The viewfinder on most SLR and DSLR cameras are LCD, which can have terrible rainbow distortions when viewed through a polarized lens (think of the earlier example of soap bubbles).
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LCD through Polar

Maui Jim polarized lenses are a little different in that their polarizing film is fused directly into the lens so delamination is a non-issue and colors are enhanced in a substantial way.  I have worn polarized lenses from at least a half dozen lens manufacturers and I always fall back on Maui Jim’s as my go-to pair–even when the prescription is out of date.

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Take Away

Polarized lenses dramatically reduced your perception of reflected light/glare while wearing them.  The technology does allow you to see chromatic structures and other things not normally visible with the naked eye.  This is less of a problem, than something to be aware of, and to know how to get around it.  While polarized lenses make the most sense for most patients, there are subsets of the population where polarized just doesn’t make sense, such as photographers and pilots.

UPDATE

A couple of comments I’ve received led to this note. Since there is an angle to the Way polar film removes glare, both eyes must be on the same angle, or plane. If they are off, they can give you a very odd sensation. In fact, 3D glasses work by having the polar film at 90 degree angle to each other, giving each eye a different image to create the 3D effect. If you have inexpensive sunglasses you can sometimes get this experience.


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Explaining Your Frames

I recently had a conversation with a friend, who was deciding between a couple of different frames.

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This got me to thinking, we never really explain the numbers on the temples of your glasses.  Each one of those numbers means something.  And here is that explanation…

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Breaking Down the Numbers

Almost any frame  you could find (that can handle an actual prescription lens) will have these numbers somewhere on it.  Typically, they are on the temple, but occasionally, you might find the first two numbers from the image above printed on the lens-facing side of a plastic nose pad.

The first number listed, refers to the eye size.  So, what does eye size mean exactly?  It’s the width of each lens, at the widest point, in millimeters.  This number always describes the width of a single lens.

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You’ll note the first number from the first image was 53.  As you can see above, the lens measures 53 mm using my PD stick (sidebar: PD stick is short for Pupilary Distance, since this is our time-tested way of measuring the distance between your eyes).  I’m going to come back to something here later, so hold onto this info…

This brings us to that second number.  Sometimes it’s listed after a dash, or a box, but it’s always the smallest number.  And it refers to the distance between the lenses.

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In this case it was 20, and you’ll notice in the photo it’s also 20 mm.  The important thing, for you, the patient, is that this number does not refer to the space your nose fits in, but the space between the lenses.  If you have a narrow nose and need a small slot for your nose to sit in, that doesn’t necessarily rule out a 20 mm size.  It all depends on how much plastic or nose pad arm is built up there in the middle.

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Finally, that big number at the end.  This actually refers to the length of the temple.  If  you have more petite features, you’ll want this to be closer to a 135.  if you’re a big individual, you may  need a 150 or even bigger.  The vast majority of frames out there come with a 140 mm temple, and this will work fine for most adults.

The Big Picture

While these numbers can all be important in finding the right fit for your face, it never tells the full picture.  As stated earlier, the way the frame is put together can change what fits dramatically.  With the frame in the photos, in particular, it’s actually pretty small for a sunglass.  A 53 eye size is pretty small, especially for my face, as a rule.  But as you can see here, it fits me pretty well.  This is all because there is a fair bit of frame outside of the lenses before reaching the temples, to go back towards my ears.

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In addition, my nose is fairly small, and I often need as small as a 16 bridge size.  This frame is a 20 and fits almost perfectly.  Again, the frame plastic is quite thick in the bridge which allows a smaller nose to still fit with a larger number (20 in this case).

Do you still have any questions?  Please ask in the comments section below.

Why Children Need an Eye Exam

Today I want to address something that patients almost never think about. We’re all guilty of this, even in regards to general health. If there’s no aches or pains, there’s no need to see your doctor, right?
WRONG.

When it comes to young children, they don’t naturally know how they should see, so they often will not express any complaints about their vision. And, unless their needed prescription is exceptionally strong, it is hard for a parent to diagnose the need by watching their child’s behavior.

Developmental Delays

If a child is not seeing properly, it can often lead to developmental delays, even before they enter school. If their near vision is not strong enough, they will have difficulty learning to read, or even having a desire to read.

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Children can have an initial exam, as young as 12 months old. A child doesn’t have to be able to read, in order to have an exam. There are ways for an eye doctor to test a child’s vision, using dilation. In my experience, unless there is the sign of a problem, I would avoid the first examination between about 18 months and 3 years, as children of that age can be more afraid of the visit, and are harder to keep still in the chair for the exam.
There was a recent study which showed that getting children into glasses as early as they need them can help to improve performance in school and prevent developmental delays.

School Screenings

The vision screenings done by schools, and by pediatricians during a physical, can be useful in spotting larger issues, but they do not test the full breadth of vision and health concerns a complete routine eye exam does.

Even if there are no vision problems, having a baseline exam very early in life can help an eye doctor spot any small changes later in life which could be signs of problems which are developing.

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Also, the earlier a child goes in for their first eye exam, and if they continue to be a routine visit, it can help eliminate the fear that children often have of the unknown in a doctor’s office.

Blue Light Concerns

You’ve seen me write about this before, it’s an especially important concern for children. There have been many reports and studies recently discussing the concerns associated with HEV, or Harmful Blue Light. Not all blue light is dangerous, but the light just above Ultraviolet is particular concerning to those of us in the optical field for many reasons.

Much of the reports about the danger to melatonin production, and our ability to sleep properly because of too much blue light exposure is overblown and inconclusive, but there is an aspect of blue light which is less known in popular culture, but much more concerning. Specifically, there have been numerous studies which show a distinct relationship between exposure to HEV and the development of Age-Related Macular Degeneration (AMD) later in life. AMD is loss of vision in the center of the retina, where we have our sharpest vision. AMD is irrerversible. Once Macular Degeneration begins, all we can do is slow it, but it cannot be stopped. The end result of AMD is blindness.

For those of us in our 40’s, this is maybe a slightly lower concern for this eventual blindness because the additional exposure we’re getting from digital devices started relatively late in life, but for our children, they are being exposed at tremendously high rates compared to us basically since birth. Anything we can do to reduce their exposure (let them use the iPad or our phones less) can help, but the best way to help us to get them into protective eyewear for when they use these devices, even if they have no prescription.

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There are dozens of lens options on the market now designed to reduce our exposure to HEV. Some do this by dramatically changing the color of the lens to filter out the blue light. Some of these do this in a more subtle way, combining light filtration from No-Glare treatment combined with lens material filtration to reduce exposure, while minimizing how “yellow” the lens appears. For a child, even one with no prescription, I would probably recommend an Eyezen lens, with a no-glare treatment. I find this lens is less yellow and therefore less distracting to a new glasses wearer. And for children, we do have to think about how these lenses might be viewed by their peers and I think they would receive less teasing for a lens that doesn’t appear yellow.

Take Away

Whether you have seen signs of visual issues with your children or not, it is critical that they receive an full routine eye exam at an early age.  Even if no eyeglass prescription is found, there are other reasons they should get eyewear to protect their eyes from the harmful blue light emitted by digital devices.  This harmful blue light can lead to blindness later in life.

Product Review: Varilux X Design

There is a constant evolution of Progressive lens technologies. While the overwhelming trend is for each advancement in lens technology to improve the patient wearing experience, there are occasional hiccups along the way which do not perform “as advertised.”

As your Optical “Jedi” I have taken it upon myself to test out as many of these new lens advancements by wearing them myself. At this stage in my optical career, I have been wearing progressive lenses for 8 years and have personally worn and tested 54 lens designs.
New Varilux X Design

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Just two weeks ago, the latest lens design from Varilux hit the market. Varilux is probably the best known brand name of progressive lenses by patients. They were at the forefront of developing the “No Line” lens back in 1959 and have continued to be amongst the leaders in lens designs.
As a disclaimer, I will admit that I have worked in many practices that have had an active partnership with Varilux and it’s parent company Essilor. This has allowed me to test more of their lenses than most competitors and I know there are many designs from competitors with great reputations. In fact, I have many lenses from several manufacturers which I recommend, based on patient scenario.

Despite my higher exposure to Varilux branded progressive lenses, I do not always feel their latest lens developments are indeed the best products available to meet patients’ needs. Often, their latest developments seem to niche, helping one type of prescription better than another.

The Review

I have been wearing my new Varilux X Design for just about a week, and not to put too fine a point on it, I’m thoroughly impressed. The wearing experience has been incredibly comfortable, and it has been one of the fastest lens adaptations I’ve experience.

There is no such thing as the “perfect lens.” Every design has some zone that is out of focus, or has issue with the vision rocking, bulging, or swimming. This lens is not “perfect” either, but it’s easily the closest to perfect I’ve experienced. According to the manufacturer, the lens was developed over 5 years of research into a different way of mapping the power distribution across the lens.

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The point of the research is to try and improve the wearing experience for the modern world. The advent of the digital devices, such as smart phones and tablet computers, have had a dramatic impact on how we utilize our near vision. Traditional progressive lens designs stagger your zones to take advantage of the way we used to look at the world (i.e. top is distance, middle is desktop computer distance, bottom is book distance). Of course, since the personal digital device explosion, the reality of where we need to see and at what distance we need to see has changed. The new Varilux X Design is attempting to address this change.

So far, I will say this has been an admirable attempt to address the issue of where we look. There are still spots where I have difficulty finding a crisp focus, but there are in the usual trouble zones of the bottom corners of the lenses. In the meantime, however, I can focus at full near while in the “mid-range” zone and I can find the mid-range in the “blurry periphery.”

The Varilux X Design lens will be going on the VSP formulary in just a couple of weeks and I have to say just after one week of wear, I’m ready to call this my absolute go-to lens for almost all conceivable patient scenarios.

Update 8/23/17

I have discovered that there was an issue with the anti-reflective coating on the lenses I received from the lab.  A small thing, but it was impacting my night vision.  After the replacement lenses were put in, I can say that the night vision clarity is also quite good.  I’ve previously worn a set of lenses specifically designed to help with night vision and I do feel that those outperformed my new pair in that situation.  But in all other respects, these new Varilux X Design lenses are better than previous lenses I’ve worn.

If you have any questions, comments, or anything else, please don’t hesitate to respond in the comments section below.  I look forward to addressing any questions you might have about glasses in the future.

Back to School!

Within days (or weeks depending on where you live), the little tykes will be leaving the home, and heading back to school. Parents will gain back some small sliver of peace and quiet (only to lose evenings, helping with homework).  With the return to school, it’s important to think about the vision needs of your kids in a new way. There are many aspects of a child’s visual needs which can become more prominent as the school year begins.

Keep in mind, if a child’s vision is not properly corrected it can cause developmental delays and adversely affect their grades and enjoyment of school.  A child cannot tell you they don’t see well, if they don’t know how they should see in first place!

The Modern Classroom

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Today’s children face very different visual demands than we did as children. First and foremost amongst those changes are the prevalence of digital devices. Virtually all children, from every socio-economic demographic, face a much higher demand on their eyes because of this increase in screen time. Even much school work is completed on tablets in the classroom and many lectures are in PowerPoint, not to mention the increasing reach of Google Classroom for their homework. All of these things dramatically impact the exposure to Harmful Blue Light for kids today.  There have been numerous studies showing a correlation between exposure and the development of Age-Related Macular Degeneration (AMD) later in life.  AMD is an eye condition which is irreversible.  Once it begins, we can only slow it’s progress and the end result is blindness.  The Macula is the central portion of the retina with the highest concentration of cones (color sensing photo-receptors).

Children today, will have a much higher lifetime exopsure to Harmful Blue Light because they are growing up with digital devices and LED light bulbs, which both put out a much higher concentration of the blue light we are concerned with.

Modern lens technologies have ways for us to filter the harmful aspects of blue light, while allowing the “good” blue light to get through.

Glare From Screens

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In addition to the concerns of Harmful Blue Light exposures, all of those digital devices create a lot of eye strain from the glare reflecting off the screens as well.  Having a good Anti-Reflective (AR) coating can help to reduce the strain caused by reflections off of devices, as well as the reflections within the lens.  In addition, there are some AR coatings which can filter even more of the Harmful Blue Light (such as Crizal Prevencia from Essilor).
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Kids Play Outdoors Too

If your child plays outside, and needs a distance correction, you probably should consider Transitions lenses as well.  These lenses adapt to light (or UV) exposure to make a lens comfortable in most lighting conditions.  They also come in three colors, so they can be cosmetically appealing to your child, as well as provide the right kind of contrast for their favorite outdoor activities.  There are other brands of photochromic lens technologies available, so make sure you are choosing the right type for your child’s needs.  Transitions has more than one version, to fit all the different lifestyle needs.  For example, there are versions that respond to any visible light, or those that respond only to UV exposure.  This is one category where personal preference becomes the most important decision making factor, in my opinion.
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Don’t Forget Sports

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The beginning of the school year also often means the beginning of team sports season as well.  From basketball, football, hockey, and volleyball, having a good pair of protective sports eyewear is critical.  There are many manufacturers of sports glasses. I don’t really want to endorse any specific brand (though I do have the greatest experience working with Liberty Eyewear).  The most important things to be looking for when choosing a sports pair of glasses are:

  • Safety Thickness (Z95.1)
  • There is silicon or rubber padding around the bridge and eye socket

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