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Bifocal lens vs Progressive lens


bkwa1959

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23 minutes ago, PrestonTom said:

If you were fortunate enough to be given your PD, then you are lucky.

No, not lucky at all, just informed. I explain that I'll be needing a prescription for progressive lenses. As I've stated, that ALWAYS includes the PD.

It's easy.

 

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I would like to thank everyone for their advice, the optometrist that I used for my eye exam gave me my PD numbers for distance and close up.I told him before  he examined my eyes I wanted those numbers for the option of buying online or from Costco or any store of my choice and he was ok with that.

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Typically, when an optometrist or ophthalmologist furnishes a pd, it is binocular.  For example, it might be 64/61 or some other combo.  This is absolutely worthless if ordering progressives since it only provides the distance between the pupils!  For progressives a monocular pd is absolutely essential- i.e. the distance between each pupil and the middle of the bridge of the nose.  Due to normal facial asymmetry, the distance is very rarely the same.  Accurate measurement requires the use of a pupillometer (a device which resembles binoculars which are placed against the bridge of your nose while the doc/optician views from the other side).  If you order progressives based on the binocular pd I assure you that the likelihood of avoiding very unpleasant prismatic effects is very low. 

 

Tom brought up the issue of seg height (the distance between the bottom of the frame and the lower lid, or pupil, depending on the type of lens).  This is absolutely critical with progressives and can only be measured with the frames of choice on your face.  Again, due to normal facial asymmetry, the seg height is rarely the same for the two eyes.  One only needs to look at typical lined bifocal wearers to see that the line is often slightly above the lid of one eye, and slightly below that of the other.  Fortunately, prismatic effects when using lined bifocals are not as critical so folks don't often complain too much.

 

Maynard

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I was told that most of the online retailers do not ask for a Seg Height when ordering, although they may ask whether you wear glasses on top or down a bit from the top of your nose. In either case, they assume the pupil will center at the mid vertical distance of the lens. You are correct, that Seg Height is absolutely specific for a particular frame (since they frequently differ from one another since the vertical distance on the frame is a function of which frame you select). Seg Height, of course, can not be part of the prescription since the optometrist can not predict ahead of time what frames you will be selecting. It will be measured by the optician, along with PD, when the order is sent (along with the script) to the lab.

 

My guess is that individual differences between the two eyes on a given person are swept under the rug by the retailer.

 

I am not entirely negative about this. The PD can be measured and will work across all frames. If the script is not a strong one (as in my case), small errors should not be too much of a problem (I am told). The big deal is that the online prices can be substantially cheaper ..... substantially!

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ca'nt type well (arm in sling)

 

I use progressive.  I'd speculate you just have to try something to see how it works for you?

 

I didn't mine the 'line', I didn't want an abrupt difference...  you (I) get used to it pretty quickly

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Coyote, I am sorry you arm is in a sling. Without a doubt there is a story behind it. 

 

I remember the first time I got my progressives, I was amazed although it took a bit of getting used to (basically you need to move your head rather than moving your eyes). 

EXCEPT ..... the first time i went down the stairs. I moved my eyes to see my feet hitting the steps. WRONG ...... I nearly fell down the steps. In the end, I learned quickly.

 

Hope your arm is is recovering quickly.

-Tom

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Here is what I got, the prescription, clearly indicating only the stereo PD, etc. They've been great. Love these things and I feel like they are still spot on for me. Over 3 years ago though.

spacer.gif
QTY   PRODUCT DESCRIPTION     UNIT PRICE   PRICE
 
1   Fatheadz Shine Glasses
SKU:   408991000045
Material:   Plastic
Frame Color:   Tortoise Shell
Size:   61 - 20 - 150   B32
Screen shot 2012-10-19 at 2.34.24 PM.jpg   $73.12   $73.12
 
    Your Lens Package
MODEL Standard Polycarbonate Progressive
LENS COATING 100% UV Protection and Scratch Resistant
TINTED LENSES FOR SUNGLASSES Dark Brown 80%

Your Prescription Information
Jeff Sargent - 5-1-14 SPHERE CYLINDER AXIS ADD PD
RIGHT EYE/OD +1.00 -2.00 95 +2.00 72
LEFT EYE/OS +1.00 -2.75 81 +2.00
  $147.00   $147.00
 
 
Subtotal: $220.12
Shipping & Handling: $0.00
Tax: $0.00
 
ORDER TOTAL: $220.12
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3 hours ago, tube fanatic said:

Typically, when an optometrist or ophthalmologist furnishes a pd, it is binocular.

Interesting. Don't these folks write 90% of the progressive eyeglass prescriptions out there? It has to be working out because they continue to do it.

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I have progressives with large aviator frames.  They make me look dignified and younger some women say.  But cute young things on the bus occasionally offer me their seat.  Dang.

 

OTOH I spend all day at a computer screen.  I had the optometrist set me up with single focus for that distance, which is about to the wrist of outstretched arm for me.  And this was a matter of having the doc set up a card at that distance (pick yours) to run the test - - "Is this better  . . . or is this better?  Much better than the progressives for that specific job.

 

One lens is quite thick (heavy).   Next time I'm going to ask about lens materials (index of refraction etc.) which might allow lighter weight, but maybe this will cause color fringing.

 

I have not tried the anti-glare coatings.   That is an extra expense.  OTOH if anyone is in a similar situation it is a matter of productivity and comfort.

 

WMcD

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The default and least expensive material is plastic (CR 39). The next notch up is polycarbonate which is a bit more expensive and much lighter (thinner and a higher index). When I made that switch years ago, I did not notice any chromatic abnormalities. I really enjoyed the lighter weight and it turns out by the nature of the material they are impact resistant and block UV. My impression is the newer high index materials may not be that big of a step up in being lighter and thinner, but they are considerably more expensive.

 

As far as the "anti-glare" coatings, there are different ones and at different price points. Such is life. The pretty advertisements at the eyeglass shop about what you will see (with and without the coating) are misleading, I asked one optician about this and he admitted that the coatings are better thought of as not being anti-glare, but rather as "anti-reflective" (IOW, the person you are talking to does not see themselves reflecting in your glasses, but their effect on driving on rainy night with headlights coming at you is minimal).

 

I get the impression that some of anti-reflective coatings are more prone to scratching. Not surprisingly, the more expensive ones have better anti-scratch components. I am meticulous and careful about this stuff, so I have not picked up any scratches in typical use with the cheaper versions. In either case, if they drop and slide along the ground all of them will scratch. I will let you figure out how I know this fact.

 

 

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1 hour ago, PrestonTom said:

I get the impression that some of anti-reflective coatings are more prone to scratching.

Not an impression, it's fact.  Found this out by experience over the years.  I'd pay extra for the "anti-scratch" and other coatings, and my glasses always kept winding up frosted and fuzzy.  Finally just said "no" to all such coatings and, by Jove, it happened only about half as fast and my glasses starting lasting for their entire prescription life.  All coatings are bad in my experience, but I haven't had any in a while and they might be better.  But my impression is they are a waste of money.

 

Dave

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This has turned into a really good discussion!

 

JL, I can only say that you are truly fortunate that your glasses work well for you.  Heck, the near pd isn't even specified on your invoice.  There's no way to predict how much adduction (inward turning of the eyes) takes place in each individual when looking at a near object.  For some it could be only 1 mm, and others 2+ mm; and the the eyes may not adduct equally.  With progressives that can make a huge difference in where your pupils will align with the reading corridor.  The fact that most eyeglass prescriptions are written by ODs and MDs has nothing to do with the measurements required to properly align the lenses with the pupils.  A perfect prescription can be rendered useless if the optical centering of the lenses is way off.

 

Tom brought up polycarbonate to reduce weight and thickness as well as being UV blocking.  As mentioned, chromatic aberration is a common problem with that material and many are bothered by it as well as the slightly less clear optics when compared with other materials.  If you need the impact resistance and UV protection which the material offers, a better choice is Trivex which has better optical properties without the aberration.  Some progressives are available in the latter material. 

 

The new generation reflection-free coatings are very durable (at least those typically used by the private opticians- the chain stores and online vendors may be using crap), and typically are no more prone to scratching than untreated lenses.  With any plastic lens, dry cleaning must be avoided unless a good micro-fiber cloth is used.  I completely disagree with Tom, however, about the coating being ineffective for glare reduction.  From situations which include working at a screen all day under the typical cool white fluorescent lighting, to reducing glare from oncoming headlights (which is of course exacerbated by a dirty windshield!), especially in the rain, the coatings can offer a great deal of relief. 

 

Maybe Klipsch should add an "optical" section to the forum.  That would certainly be unique in the audio world!  We could discuss which lens types, materials, and coatings allow us to see our Klipsch speakers more clearly......

 

 

Maynard

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  • 2 weeks later...

I just received my progressive bifocals today and it is going to take some getting use to,looking straight ahead everything is fine,my side vision is fuzzy,as long as I focus on what I am looking at it is fine,just seems like my lined bifocals had a wider range .

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1 minute ago, WillyBob said:

 I dunno folks. I have been wearing glasses for 50yrs+...

nearsighted.... I cannot read billboards w/o them ....  do it the old fashioned way.

Look under the lenses or take them off when I am working close

The problem with that is your head movement is more exaggerated when you try to look under them.  I am only 49 and don't like to look like an old grandpa who won't pay for a good set of glasses.

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30 minutes ago, Jeff Matthews said:

The problem with that is your head movement is more exaggerated when you try to look under them.  I am only 49 and don't like to look like an old grandpa who won't pay for a good set of glasses.

Come on Gramps, you're just 10 years to 60--Hahahahaha

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On 2/3/2018 at 7:28 PM, PrestonTom said:

Coyote, I am sorry you arm is in a sling. Without a doubt there is a story behind it. 

 

I remember the first time I got my progressives, I was amazed although it took a bit of getting used to (basically you need to move your head rather than moving your eyes). 

EXCEPT ..... the first time i went down the stairs. I moved my eyes to see my feet hitting the steps. WRONG ...... I nearly fell down the steps. In the end, I learned quickly.

 

Hope your arm is is recovering quickly.

-Tom

 

 

Always a story huh?  :o

 

Someone was coming over to get my MWM cabinets (for free).  They were stored in a trailer (Semi/tractor/trailer).  Floor of the trailer is what... about 4' off the ground?  

 

I was standing inside noting how big they were and felt I should go get a strap so we could perhaps slow their fall/slide out of the trailer.

 

Was at edge going to get out, slipped and essentially dove head first into the ground.  My head barely hit the ground, but the point of my shoulder took the full brunt.  Roughly 4' for the floor and the shoulder is about 4' up...  so approximate 8' fall onto the ball.

 

Broke the arm bone about 2-3 inches below the ball.  Ortho said bad news was, broke 100% but the good news was, it was a clean break, everything is in perfect alignment so no surgery.  I'm in one of those imobilization slings with my right arm (I'm right handed to make things worse)

 

Wish I could blame it on my bifocals (to keep it on topic) but  if I were to be honest, I think it was just a dumbazz accident.

 

Sling for 4 more weeks, go back for another X ray then graduate to a "normal" sling.  Said it would probably be 8 months before I was back to 100%

 

 

I ordered 2 more pair of glasses other day.  Got progressives again.  Decided to go all out.  Did the anti-glare (which they said was actually part of the way the lens was made (Zeiss) rather than an add on (??), did the transitions...  Gal said she didn't think she had yet seen anyone come in that had as nice of coverage as I had.  ($250 limit per pair or swap a pair for contacts)

 

Decided to get two different styles.  Due to arrive in about a week.

 

In the meantime, I'm going to stay clear of all trailers!!

 

(ever try to pull a t-shirt over your head with a usless arm that is willing to stab you with intense pain if you move it too much?  Getting dressed has turned into an intersting  challenge every day)

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8 hours ago, Coytee said:

 

 

Always a story huh?  :o

 

Someone was coming over to get my MWM cabinets (for free).  They were stored in a trailer (Semi/tractor/trailer).  Floor of the trailer is what... about 4' off the ground?  

 

I was standing inside noting how big they were and felt I should go get a strap so we could perhaps slow their fall/slide out of the trailer.

 

Was at edge going to get out, slipped and essentially dove head first into the ground.  My head barely hit the ground, but the point of my shoulder took the full brunt.  Roughly 4' for the floor and the shoulder is about 4' up...  so approximate 8' fall onto the ball.

 

Broke the arm bone about 2-3 inches below the ball.  Ortho said bad news was, broke 100% but the good news was, it was a clean break, everything is in perfect alignment so no surgery.  I'm in one of those imobilization slings with my right arm (I'm right handed to make things worse)

 

Wish I could blame it on my bifocals (to keep it on topic) but  if I were to be honest, I think it was just a dumbazz accident.

 

Sling for 4 more weeks, go back for another X ray then graduate to a "normal" sling.  Said it would probably be 8 months before I was back to 100%

 

 

I ordered 2 more pair of glasses other day.  Got progressives again.  Decided to go all out.  Did the anti-glare (which they said was actually part of the way the lens was made (Zeiss) rather than an add on (??), did the transitions...  Gal said she didn't think she had yet seen anyone come in that had as nice of coverage as I had.  ($250 limit per pair or swap a pair for contacts)

 

Decided to get two different styles.  Due to arrive in about a week.

 

In the meantime, I'm going to stay clear of all trailers!!

 

(ever try to pull a t-shirt over your head with a usless arm that is willing to stab you with intense pain if you move it too much?  Getting dressed has turned into an intersting  challenge every day)

Sorry to hear that, heal up quickly.

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