A Word about Frame Adjustment and Maintenance

I know I announced my brief hiatus, but I wanted to talk a little bit about frame adjustment and its importance to the wearer.

If your eyeglasses are not fitting properly on your face, not only are they uncomfortable, but it also adversely affects the quality of your vision through a variety of ways.

Examples

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If you have any astigmatism correction, and your glasses are crooked, then you are getting the incorrect prescription. As discussed in my previous article on correction found here, astigmastism correction is set on a specific axis. If the glasses are crooked you have changed the angle of that astigmatism correction on each eye, negatively impacting the clarity of your vision.

Glasses are made to sit on your face at a certain distance from the eye. If that distance is elongated, you are changing the magnitude of the correction. So, as glasses slide down your nose, you actually make your lenses less nearsighted, or more farsighted. Whatever your real correction is, this is something you want to avoid.

Glasses need to have a certain amount of tilt towards your cheeks. This provides the best clarity. If your glasses end up too tilted towards the cheeks, or not enough, then you reduce your clarity again.

Progressives compound all of these issues. If a progressive is worn crooked, then you end up with one eye looking through the distance, while the other looks through the intermediate. AND your astigmatism correction is also wrong at the same time!

Take Away

So what’s the lesson here? You take your car in for a tune up and oil change every 5-10,000 miles, why don’t you take your glasses in for a tune up too? A good rule of thumb is every 3 months or so. The frequency may vary based on your local weather. Hotter climates tend to mean frames will stretch out and get crooked faster. Going in frequently also means that your optican can tighten all screws, give the frames an ultrasonic bath to remove makeup and sweat build-up, and your glasses can be inspected for scratches or warranty issues.

Your optician is your friend. Visit him or her frequently!

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Very Brief Hiatus for the #JediLine

As most of you know I am intimately involved with LiningUp.net and the Star Wars lines we produce at the TCL Chinese Theatre IMAX in Hollywood California.  As our line for The Last Jedi starts in just one week, I will be tied up with many responsibilities to help this charity event take place and will be putting this blog on a very brief hiatus.  I will be back up with new posts after December 16th. You can follow my exploits as member of the Social Media Team on Twitter and Facebook. And if you would care to support our endeavors to raise money for Starlight Children’s Foundation, you can donate here! Since 1999 we have raised over $100,000 for this excellent charity.

In the meantime, I will continue to respond to any messages or emails you may have for me.  May The Force Be With You

Review Update on Varilux X Design

I posted an initial review of the latest progressive lens from Varilux, the X Design, when it first launched back in late August/early September.  My initial review can be found here.  After wearing the lenses for a couple of months, I wanted to provide an update based on my continued observations.

Review of Varilux X Design…Continued

As you may recall, my initial review of the latest progressive lens from Varilux, the X Design, was glowing.  My experience of the near and intermediate zones was phenomenal.  After wearing continuously for over two months, I still find this to be true, but I do wish to get a little more detailed on the experience.

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Breaking down the Distance

I believe I have found how they improved the intermediate and near so much.  The width of the distance zone is noticeably smaller.  While it’s not so small I would call it problematic, I think it’s important to note that if your needs are exceptional crispness and width of field in the distance, you may want to pause before going with the Varilux X series.

My initial thought when I noticed the smaller distance zone, was that perhaps my glasses weren’t properly aligned.  I suspected that my pupils might be sitting on the edge of the intermediate zone and that was why I was having issues.  But I remarked my lenses and took note of placement…even making small adjustments to how they sat on my face…and I could not increase the width of my distance vision.

The vast majority of my visual lifestyle takes place in the intermediate and near zones.  All of my work with patients, on computers, and phone/reading.  However, I am also exceptionally picky about my distance vision and I am a dominant eye-turner.  Rather than holding my eyes straight ahead and move my neck to align my vision, I tend to look out of the corner of my eye and expect to see sharply.

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Note the black dots on lenses to note corridor position

This has led me to rethink my initial glowing review of the X series.

Intermediate – Arms Length

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The zone of the lens dedicated to arms length (think your computer monitor, or dashboard in your car) is excellent.  Both the width of this zone, as well as the depth of field is very good.  The depth in the corners of this zone is not quite as good as the center.  So, if you need to see something closer than you’d expect at that height, it needs to be in the center of the zone, and not out of the corner of the eye.  Still enough quality width, clarity, and depth to highly recommend if this distance is critical for you.

I have noted that patient experiences have varied a bit on the quality of this zone, based upon how tall their lens is (how much distance from their pupil to the bottom of the frame).  Those with a longer corridor, or a stronger add (over +2.25) seem to find their intermediate zone a little lower.  This can still be fixed with adjustment of fit to a great degree, but it is something to consider if the frame you choose has your eyes very close to the top of the lens and it’s oversized.

Near Zone – How’s the Reading?

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The reading-or near zone, has a similar wearing experience as the intermediate.  The width of the zone is very very good.  If you want to see something at arms’ length, then you’ll want it closer to the middle of your lens.  But there are a couple of spots in the periphery where the intermediate distance becomes quite good.  You do have to hunt for this location just a bit.  When it pops in for intermediate it’s very very good though.

Does it Work for All Prescriptions?

So far, after fitting this as my primary progressive lens for over two months, I have found that there seems to be a broad range of prescriptions which can wear this lens design effectively.  So much so that I would not say there is any specific power limitations for a good wearing experience.

Take Away

I still feel that the X Design lens is an excellent choice for the vast majority of patients.  I still love wearing the lens.  There is a peripheral loss of clarity in the distance portion of the lens, but it’s still far enough to the corners of the lens that I don’t find it exceptionally annoying or distracting.  If you need to have super crisp edge to edge distance vision, this lens design may not be for you.

While every lens design that comes out claims to be the salvation that fixes all the problems for all patients, this has yet to be true.  The X series comes very very close to doing this, but it’s still not quite the magic pill.

*please note that I have been wearing and testing the Varilux X Design.  The X series refers to a collection of 3 related lens designs, the X Design, the X Fit, and the X Fit 4D.  I have not tried the other two lenses in the family of products.

Lens Materials Advantages and Disadvantages

First things first, I would like to apologize for my extended absence.  Halloween season with a 9 year old means lots of time spent on costumes and parties.  Pair that with a small round of being sick and, well, here we are a few weeks later.

Today I’d like to spend a little time discussing the many materials that can be used to make prescription lenses.  There are many solutions to fit the many needs of different prescriptions and lifestyles.  There is no, one single best choice.  But I will break down the advantages and disadvantages on each material to help you navigate the best choice for your needs.

Abbe Value

No, Abbe isn’t a girl who works at the lab.  This is a number used to define how much aberration (distortion and/or color separation) occurs in a lens material.  The lower the number, the more distortion there is inherent in the material.

 

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Now, I know these numbers by themselves won’t mean much to you.  But the essence of these numbers is that glass has the best optical quality available.  The trade off, however, is that glass is also excessively heavy (especially for a higher prescription), and it’s less safe as a rule given the brittle nature of the material.

Herein lies the rub.  The best optics almost always come with a trade off on weight and durability.  The lighter and thinner materials are more comfortable and cosmetically look better for higher prescriptions, but that does come with an optical clarity trade-off.

Index of Refraction

Refraction is the term used to describe how much light is bent when it enters a medium.  When we are talking about glasses, we’re always talking about the lens material.

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The a 1.0 index of refraction would indicate that the light is not bent at all.  Any number of 1.0 is indicating that the light is entering a different material which bends the light more dramatically.  The higher the number, the more the light is bent, and therefore the less material needed to correct for a high prescription.  Thus a 1.74 hi index plastic bends the light more than a 1.50 standard plastic (CR39).

The more the light is bent, the thinner and generally lighter the lens material is, but that extreme bending also means some light is lost to the prism effect (color aberration).  That is to say, lower abbe values separate white light out into its separate color components and you may actually see a small rainbow effect around the edges of things.

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This aberration is why it’s so important to take the additional measurements of not just pupil horizontal position, but also vertical position on a patient with a higher prescription.  These chromatic  aberrations can become very intrusive with hi index materials.

 The Polycarbonate Reputation

Polycarbonate has traditionally had a very bad reputation.  In part this is the same old story as Transitions.  The older versions of the material from 30 years ago were quite inferior.  Lots of aberration, chromatic distortions and very small optical centers.  In part it was the manufacturing process used at the time.  Over the past couple of decades the manufacturing of this material has improved dramatically.  You can still get “bad batch” versions with terrible distortion, but they are relatively few and far between.  I think it does say something to the improvement of the material that I wear polycarbonate almost exclusively in my glasses, and have for the past 10 years. It can be a good choice as long as your prescription isn’t too strong.

Choosing the Material for You

As you can probably guess from all the above material, the general rule of thumb is to go with the highest abbe value (meaning the least amount of aberration).  But this has to be balanced against the power of the prescription, and the impact resistance necessary for lifestyle.

For these reasons, polycarbonate (for better or worse) has become the most common lens material in the optical industry…at least in the USA.  While it does not have the best abbe value, it does have impact resistance.  It has a relatively wide range of prescriptions which can be corrected before chromatic aberration becomes an issue, and it is has a plentiful number of lens design solutions available (Transitions, progressive designs, glare treatments, etc.).  Is it the best solution?  I’d say probably not.  Is it the easiest solution?  It’s the safest bet of protecting the eye and giving decent visual acuity, while still having access to all the different ways of correcting vision needs.

All things being equal, I think I’d prefer to work with Trivex for most moderate corrections, but the limitations on progressive designs and transitions colors available keeps me from going to it frequently myself.  In fact, I wear polycarbonate for my lenses.

However, if your prescription is either above a +3.00 or a -4.00 I generally recommend considering high index to control some of the chromatic aberration and to provide a cosmetically thinner lens.

Take Away

There are many lens materials available, and finding which one best suits your needs comes down to how strong your prescription is, and how shatter resistant do you need your lenses to be…but in the end polycarbonate is often used just because of accessibility and safety, even if it isn’t always the best optical choice it’s still a decent choice for most common prescriptions.