Problems with "poly" variants - can someone please explain?

I tried "poly" lenses 5 years ago and found them uncomfortable, so my
lenses were switched to "plain plastic" and I've had no issues. I opted
for new frames after a recent exam (same Rx) and went for Silhouettes.
I was told that only poly lenses can be used in them. I reminded the
optician about my previous encounter with poly, so he suggested Trivex.
Well, they gave me problems. It fealt like what I remembered dirty
contacts to feel like (20 yrs. ago). So, they ordered "hi-index 1.60"
lenses. They are better, but I still have some minor discomfort after
4-5 days. I called my opthomologist and he said some people get used to
"poly" and some never do. Ironically, my old lenses are sooooo
scratched, yet that doesn't bother me except when it creates a large
glare.

My prescription is -250 -250. These lenses have polished edges.

I have read a number of posts here, but lack the training to fully
understand the issue and lens options.

Can someone explain the difference between poly, Trivex, and high
index? Also, are there are other lense options for these frames (I
think they said 1.80)? And if I'm out of options, should I try to get
used to them for a while or can this cause harm in any way?

Thank you very much.

 

BTW - I have also been wearing Oakley prescription sunglasses for about
4 years and they are the most comfortable glasses I've ever had and no
issues at all. I believe they're "poly" so ???????????

 

Thanks Robert. The store went from my measurements on file from my
plastic lenses and didn't check me for this purchase. Who should "Check
the vertex distance, vertical and horizontal OCs, panto, and look for
warpage, waves and surface imperfections."? Is that something the store
should do or at this point does that require an opthomologist?

 

Poly is OK when there is now lens power.

 

There are two kinds of lens that have high impact resistance and high
tensile strength. One is polycarbonate, which has an index of about 1.59.
Polycarb has the lowest (worst) "abbe value" of any generally prescribed
lens (abbe value is 30). Abbe value is a measure of chromatic aberration,
the higher the better.

The other lens with high impact resistance and high tensile strength is
Trivex (sold mainly by Hoya and Younger in the US), which has index of about
1.53. Therefore your lens will be thicker and heavier than a higher index
like polycarb, but Trivex has an excellent abbe value of about 43. Some
people say that Trivex has a slight tint to it, but if you put on a high end
AR coating, then you may not notice it. I don't understand from your post
above exactly what your problem with Trivex was, so it might help if you are
more specific.

Both polycarb and Trivex are very good for lenses that are drill mounted
because of their very high tensile strength and resistance to cracking.

Other "plastic" lens materials are available from 1.50 index (called CR-39,
hard resin, or regular plastic) all the way up to about 1.74. usually the
higher the index, the lower the abbe value (worst the optics), but the
higher the index lenses will be thinner and lighter (because less material
is needed for a given lens power).

For a -2.50 (it is not 250) Rx, which is low to moderate in strength,
getting a lens with an index higher than about 1.55 is not necessary to keep
the lens thin and light. For the best optics, you should get the lowest
index lenses you are comfortable with. 1.80 is not widely available in the
US, and is completely ridiculous for someone with a -2.50 Rx (it might be
needed if your Rx is -12.50) and is one of the few lenses that would be
optically worse than polycarb.

Trivex (1.53) should be thin and light enough for your Rx, and is very good
for drill mounts, and has excellent optics. I would try to find out exactly
what lens you have and exactly what was wrong with the Trivex lenses you
tried. Most people who have tried Trivex are very satisfied with the optical
quality.

 

Mark, thank you for the detailed explanation. The moment I put on the
Trivex in the store I felt discomfort, particularly in my left eye.
Within 2-3 minutes of wearing it in the store for the first time, my
wife and the optician noticed my left eye becoming bloodshot. Most of
the time wearing it I would feel discomfort on my eyeball, as I said,
like an irritation the way I remember dirty contacts to feel. Possibly,
there was a little more tearing too.

Today, I wore the 1.60 lenses for about 11 hours and they were
bothering me to a lesser degree. Within 15 minutes of switching back to
my old (same Rx) scratched plastic lenses the discomfort was subsiding.
I can only imagine it has something to do with how light or the
magnification is being presented to my eye (????) but that still leaves
no path to a solution. Currently I'm trying to train my eye to these
lenses, but today's "training" doesn't look promising.

Still looking for solutions...

 

I very much doubt your problem has anything to do with the Trivex lens
material, if that truly is what you received.

The number of errors in grinding lenses to the correct power and fitting
lenses (for proper placement in the frame so it is optically centered) is
much higher than you would suspect. And there are sometimes errors made
during an eye exam by an OD.

Any time you have a problem like you had with the Trivex lens, you need to
take the lenses to another optical shop and have them measure the Rx of your
new and old lenses. You also may need to move the frame around on your face
to see if the lenses are the proper distance from your eyes, are at the
correct angle, and are optically centered.

Anytime you are dissatisfied, ask for a second opinion from a different
optician or OD. Do not even talk to young sales people in a Optical shop,
always talk to the most experienced person you can find.

I would really like to know what kind of optical shop you have used (large
chain, local independent, optical shop in OD office, etc.).

 

Mark, thank you again. I originally was examined by an Ophthalmologist
who confirmed that my existing Rx (-2.50) was still correct for me. I
then went to the optician I have used for the past 6 years to get the
glasses. They are located in a large mall, but I'm not sure that they
are anything but an independent operator. They have been very
cooperative, but again, used my on-file specs. for this order, without
re-measuring. I've never had an Ophthalmologist provide anything but
the basic lens power on the Rx, leaving the rest to the optician.

The message I'm getting from you is that Trivex was a better product
that may have been produced wrong for me. I basically asked about that
and when I first went back, they measured them and said that they met
the proper specs. (???)

I called the opthamologist's office and they said a small # of people
don't adjust to poly (I specifically said Trivex).

I don't know where the Trivex lenses are now, but my understanding from
you is that I'm on the wrong path with high index. The optician has a
store credit only policy, so I'm bound to them. I would like to make
these frames work for me but don't know who can determine the real
issue or where to turn to resolve it? Are there people who don't adjust
to properly made Trivex?

 

Given that Trivex has an abbe value of 43 and is considered to be one of the
best materials in terms of optical quality, I don't think the Trivex
material is related to your problem. It could be the lens design (lens make
and model), the grinding of the lens, or the fitting of the lens in the
frame so that it is optically centered. Trivex is not the same as polycarb,
so I don't understand the comment from your Ophthalmologist about not
adjusting (but Trivex is relatively new and not everyone is familiar with
it).

I would suggest that find out the exact make and model of the Trivex lens.
There are only 2-3 lens suppliers in the US (Hoya and Younger are the main
ones) that are licensed to use Trivex material.

Personally, I would not recommend an ophthalmologist for an eye exam. They
are medical doctors who spend most of their time with eye diseases and other
serious eye problems, while Optometrists (OD) spend all their time doing eye
exams. However, if you do have an eye disease, then stay with your
ophthalmologist.

I notice that you did not specify a correction for astigmatism in your Rx.
Is that correct or did you just leave that part out of your post. It is
somewhat unusual to need any correction for astigmatism, but not totally
unheard of. Also, I am assuming that you have single vision lenses and not
progressives, since you did not state an "add" power for the reading area.

For a simple single vision -2.50 Rx, you should be able to easily find a
pair of glasses that give you good vision without any problems. As I
suggested earlier, if you have any doubts about a lens, then you should take
them to another optician to have them measured. Or your could take the lens
made by the optical shop to your ophthalmologist. Have them compare the old
(good) and new lenses.

When purchasing a lens, always make sure you know the lens manufacturer
(Hoya, Younger, Sola, etc), the lens model, and the lens material. Otherwise
you may be purchasing substandard products. If they don't know, or will not
tell you, go somewhere else.

You would not believe the number of mistakes that are commonly made in the
process of making glasses, and the optician may not be able to recognize
their own mistake. About 15 years ago, I purchased a pair of single vision
lenses from EyeMasters (at that time owned by Sears). When I got the
glasses, I immediately told them I could not see anything out the lenses.
Several employees re-measured the lens power and they said it was correct.
Finally, after much complaining, I found another employee who realized that
the astigmatism correction (cylinder and axis) was ground backwards. This
kind of gross incompetence is not rare.

 

Thanks again. No disease/issues. Single vision. No astigmatism. Same Rx
for at least 10 years. Oakley's "proprietary" poly Rx sunglasses no
problem for me. So is there this issue that some people don't adjust to
Poly? And if so, that doesn't apply to Trivex? Am I correct that the
Trivex lenses have to be checked installed in the frames?

 

Some people are more sensitive to polycarb distortions than others, and it
is more noticeable when the lens power increases. Moderate to high power
plus lenses (+) have more of a problem with polycarb than minus (-) lens
powers. If you have Rx sunglasses in polycarb, some of the problems (such as
chromatic aberration) may be less noticeable because of the tinting.

Trivex does not have the same problems as polycarb in terms of "adjusting"
to the poor optics, because Trivex does not have poor optics. The only
downside to Trivex is that it is lower index (1.53) than polycarb (1.59),
which means that it is thicker and heaver for a given Rx, but that should
not be much of an issue for a -2.50 Rx. Trivex also has a slight tint to the
lens, but may not be noticeable if you have AR coating.

Trivex is usually more expensive than polycarb, and only available from a
few lens manufacturers, notably Hoya and Younger, (but maybe 1 or 2 others
have recently starting licensing it). Do not be surprised if an optician
claims they ordered Trivex, but actually ordered something else. Find out
the lens manufacturer name and model number of all lenses your purchase,
especially Trivex.

 

Mark, you are a wealth of information! Do you work in the industry?

I went to both the Hoya and Younger web sites to look up their info on
Trivex and I don't see any listing for it. I see that PPG makes the
material - do they use PPG material and then brand it? If so, do you
know which is which? Also, I ordered both lense types with the Cryzal
coating - any thoughts on that?

 

Given that Trivex has an abbe value of 43 and is considered to be one of the

An Abbe value of 43 does not sound terribly good, as I find (using
Google) that CR39 plastic has an Abbe value of 57.8, almost as good as
glass. 43 is less than halfway between this and 35, the Abbe value of
polycarb.

Is there some other aspect of Trivex that makes it have good optical
quality?

Liz D.

 

Hoya sells it as "Phoenix" and Younger sells it as "Image".

If I had a choice, I would use Hoya Phoenix.

Crizal, and the easy to clean Crizal Alize. are both excellent (durable) AR
coatings. Crizal is made by Essilor, but is available on some other
manufacturer's lenses also. But I would be a little suspicious of Crizal on
Trivex, since Essilor does not offer Trivex. As I said, some labs will put
Crizal on other lenses beside Essilor, but I would double check that.

You should be able to get a finished -2.50 lens from Hoya that comes with a
Hoya AR coating applied by the factory. A finished lens does not have be
custom ground at a local lab, which eliminates one more variable in the
process.

 

Every polycarb that I have seen has an abbe value of 30. Where did you see
35?

Actually, polycarb has some additional distortions (besides chromatic
aberration) over and above most other lenses that are not measured by the
abbe value.

Yes, CR-39 (1.50 index) has a very high abbe value, but it is thick and
heavy for someone who has more than a mild Rx, and most people wear high
index lenses these days (usually 1.60, 1.67) which have an abbe rating of
about 34-38. And of course polycarb (1.59) is often used and has an abbe
value of 30. So an abbe value of 43 is quite good for a lens with very high
impact resistance and very high tensile strength. This is an issue for the
OP who wants drill mounts for his frame.

Aside from being good for drill mount frames, polycarb and Trivex are the
only lenses that are approved for those who need "safety" lenses, such as
children, those who play sports with glasses on, or for someone who works in
a lab or factory. In the US, all opticians have a "duty to warn" customers
that they recommend polycarb lenses for children or for other people who
have need for safety lenses. Often times polycarb is sold to minimize legal
liability, rather than to provide good vision.

 

Mike, thank you for the added input and test idea.

In my house now I can only test myself to about 40 feet of distance and
for comparison I tested with both my old glasses and the new
(currently) high index lenses. It's hard to say for sure what the exact
results are but here goes:

I thought sometimes w/the old lenses one eye saw the object a little
larger than the other (??) but not much in the way of movement vert. or
hoiz.

Most of the time with the high index it seemed like there was a little
change diag. affecting the object height a little. (??) Sometimes I
wasn't sure.

My eyes are tired now...

Should this be done outside with real distance? I'm guessing this is
only a preliminary means to make a judgement and that true lense
measurements are needed. (??)

As far as I can tell both the Trivex and high index lenses have been
crystal clear to me. No blurring, no waves, and causing no headaches.
The discomfort with the Trivex started (as I described) like the way I
remember dirty contacts to feel (from 20 yrs. ago) - kind of
itchy/irritating. Both lense types cause an ache in my eyeballs (feels
like the schlera area) - particularly on the inner sides adjacent to my
nose and sometimes towards the bottoms. As the hours pass while wearing
the glasses the ache increases from a very mild discomfort to enough of
an annoyance to put my old scratched up glasses back on. 15 minutes in
those and the aching is disappearing. I believe the high index cause it
less than the Trivex did, but I don't have the Trivex to compare
side-by-side. I can't see wearing them day after day and having this
discomfort, let alone wondering if there's a physical effect taking
place on my eyes.

I was a mechanical engineer w/NO optical training. So my layman's guess
(emphasize guess) based on the way my eyes feel, is that they have to
focus towards the outside (left and right) and strain the inner side.
But of course I don't know.

Thank you.

 

MT,

I did not respond to your original post, because I have you in my killfile
for the absolutely ridiculous arguments you get into with the quacks on this
forum. Or maybe you are one of the quacks, I don't even remember. But I did
see that your post above is included on the response of the OP, so I will
respond.

Since I don't work in the optical industry, it is not even remotely possible
that I have any marketing agenda. Polycarb, with an abbe value of 30, has
the worst optics as any other lens that is generally dispensed in the US.
That is a fact. Indexes beyond 1.74 is not widely available and not
generally dispensed in the US.

I never suggested that the problems of the OP had anything to do with
polycarb, since (as you pointed out) he did not complain about "rainbows",
swimming (which can occur with SV polycarb), or even peripheral distortions.
Likewise, I suggested that the problems with his Trivex lens had nothing to
do with the Trivex material. I did point out that Trivex is substantially
better in terms of optical quality than polycarb (which is absolutely
indisputable), even though they both share high tensile strength and high
impact resistance.

What I did suggest (in multiple posts) is that his either Rx is bad, or the
lenses were not made correctly, or the lenses were not fitted correctly. I
asked him to get the lenses check at a different optician, and to also try
an OD for his eye exams.

It is no wonder that you are in my killfile, and you should be in everyone's
killfile.

 

I don't get an itchy feeling like an allergy. It's more of a
strain/annoyance in the areas I indicated. There is no redness. That
happened the 1st time I wore the trivex, more in the left eye. No
visible reactions like puffy lids.

 

Wow. You KILLFILED Mike Tyner??

Does ANYBODY get through your killfile??

 

It was hard to get a useful definition of Asthenopia until I found the
one at: http://en.wikipedia.org/wiki/Eye_strain

Yes! Yes! That's a broad definition of what I'm experiencing -
particularly to what I believe is the ciliary muscle.

I'm headed off to the opthomologist's optician later to see what she
can determine from the glasses. I'll update here later...

Thank you all again!