Progressive Lens Questions

I am converting to conventional glasses from my Lear Vision aviators
that I have been wearing for the past 15 years (with worsening
presciptions) due to inability to replace them with a similar
suspension system as they and similar ones appear to be unavailable
(if you know of one, I would love not to have to change). We have
settled on Silhouette Titanium 7458 50.2Y 12 (????) shape and size as
they seem the least obtrusive and least uncomfortable of the
conventional styles and the lens seems large enough to be practical,
not tiny peepers.

My new prescription is:

-125 | -150 | 92
-100 | -150 | 90
ADD: +225 P.D. 65 / 62

I have been wearing progressives, no idea what make lens was used in
the Lears, for many years and am quite happy with them. Now the lens
choices are so numerous, and the limited information available to a
consumer about their features so nebulous and pretty much useless (at
least to me), that I am totally confused as to what will work best,
especially with this new prescription (about 1/4 diopter worse
overall). I spend about 10-14 hours a day in front of the computer
(21 inch monitor at 1024 x 768) with a distance from my eyes of about
25 - 37 inches (mostly closer rather than farther). I am also a
general aviation pilot, so both close and far vision is also critical.
As I noted, my current glasses have worked great, but...

The optician we have been working with (Paris Optique in Chandler, AZ)
has recommended a Varilux Comfort polycarbonate lens with Crizal
coating. Is this the best choice or are there other alternatives that
might perform better for me.

Also, he has recommended clip-on sun lenses. Given the extreme high
cost of the Silhouette glasses (4 times what I paid for my Lears a few
years ago!) that sounds like a good idea to at least try. Cannot use
the Silhouette clip-ons as they are apparently only available in
polarized, which are unacceptable in the cockpit. They also don't
seem to be able to be put on without taking off the glasses, whereas
the others shown to me can be done without removing and messing with
them. The alternative ones he showed me that would exactly match the
lenses in the Silhouettes weigh more than the glasses, it seems the
metal parts are not lightweight material. Does anyone make
matching/custom clip-ons that are made with lightweight clip and
bridge (titanium?) materials?

TIA,

Doug

 

Varilux makes good progressives. The Panamic is top of the line and Comfort
is just below that. For your moderate Rx, Comfort will probably work fine.
Crizal is an excellent (fairly durable) AR coating. I say "fairly" because
all AR coatings are much more fragile than an uncoated lens.

Polycarbonate (1.59 index) has very high tensile strength and impact
resistance (required for some safety applications), but relatively poor
vision (especially in regard to chromatic aberration) compared to other
lenses. But people with weak or moderate correction "usually" do not have a
big problem with them. Polycarb is somewhat thin and light, and is easy to
drill for rimless frames (high tensile strength). The Comforts also come in
regular plastic (1.50 index), and 1.60 index plastic, both with better
optics than the polycarb.

If you have the bucks and need lenses with high tensile strength and impact
resistance, Trivex lenses (1.54 index) have MUCH better optics than
polycarb, but have a slightly lower index and therefore are little bit
heaver than the same polycarb lens. Trivex is sold as Hoya Phoenix or
Younger Image lens material (currently not available from other
manufacturers). The Hoya ECP progressives typically get good reviews.

There are many other lens choices. Many people like progressives from
Rodenstock and Zeiss, but they may be more expensive and in some cases take
a few weeks to have made.

Almost all progressives have markings on them that can identify the lens.
Your optician should be able to id your current lenses. If not, check with
another optician. Based on my experience, most Wal-Mart opticians will id
the lenses, and they may also quote you a price on the Comforts.

 

As with all technologies I generally look to the latest designs. An
interesting article on "personal progressives" is at
http://www.visioncareproducts.com/29/lens_age.html. The Rodenstock
Multigressiv atoric lens is often recommended for astigmatism. The
J&J Definity is also an atoric design. Among newer but more
conventional designs the new SolaONE looks interesting with its Teflon
AR. The Hoya Summit ECP which I wear appears to benefit from similar
visual simulation technologies as the Sola, and Hoya makes substantial
durability claims for its new AR. The dimensions of your frame will
limit to some extent determine your lens choice.

All the above designs will be more expensive than the older Varilux
Comfort. All are produced only at the manufacturer's facility, and
some opticians may be less inclined to recommend a lens that can't be
ground at a lab they have a relationship with; you may have to ask
around.

I have no trouble snapping on and off the Silhouette clip-on while I'm
wearing my glasses (takes a little practice but quickly becomes second
nature). They're far less likely to scratch the lenses than any
conventional clip-on. And my glasses even fit into the Silhouette
case with the clip-ons attached(!). May not work for flying but
definitely something to consider for everyday use.

 

Varilux lenses are only ground at certain approved labs, although because
its popularity, there are a lot more labs that finish Varilux lenses than
Hoya in the USA. The Comfort is not the latest Varilux design, which is the
Panamic, but works well for mild to moderate correction, and is less
expensive.

Comparing progressives is always difficult, but I actually found one
optician who claimed that the Varilux Panamic (his wife had them) was much
better than the Hoya ECP. Interestingly, he sold the ECP, but not the
Panamic.

 

Mark A wrote:
....

....

Well, here is a real stab in the dark, but I'm hoping some experts
really
exist here.
I went to get new lenses (and frames...) and started to run into some
terms that just baffled me. Actually it was the ignorance of the people
at the optics shop that baffled me.
They used the terms: polycarbonate, "regular plastic" and hi-index.

I near to barfed when I heard the term regular plastic. That is
like saying
a building is made of materials or a food recipe is made of ingredients.
In about a half-hour I could find on the Internet that this regular
plastic
is probably CR-39, an Allyl Diglycol Carbonate. Now that does mean
something, even if the 'an' is still not specific. But I'm satisfied
for now.

So ... can anyone tell me the more specific name of the polycarbonate
(1.59 index) as used in the optics field and referenced above?
(CR-39 seems to fit in the polycarb family as it is a carbonate and is
polymerized. But being 'special', it became 'regular' - such is the
way of commerce.)

All I get on the other names is 'proprietary' - OK - keep it a
secret, but
could I at least get the general family for 'hi-index' materials, such as
mentioned above? That is what I got in my frames as I type, but
as it took 15 trips to various eye exams and the optics shops, I
have about had it with asking questions the clerks and Docs do
not seem to understand. What are these made of????

And to make a real challenge - can I somehow, someway, possibly
get a few sample blank disks of some of these various plastics used
for optics? I've got plenty of PMMA for my experiments and a choice
of sources in a wide variety of shapes. But I'd like to toss a few of
these other clear polys into the mix to see what comes out.
Do I have to join a priesthood to access these esoterica, or should I try
the Hamfests for surplus materials?


Regards,
Wm. Hathaway

(See teslamania.com for examples of our experiments

with PMMA.)

 

I am not a lens expert, but regular plastic (CR-39) is very different than
polycarbonate lenses used for glasses. It is different in refraction index
(1.50 vs. 1.59), optical quality (58 abbe value vs. 30 abbe value), specific
gravity (1.32 vs. 1.20 g/cm3), tensile strength and impact resistance
(polycarb is MUCH higher and required/recommended in certain situations). I
don't think that CR-39 could be considered a polycarbonate as the term is
used in the optical industry.

An optical chain normally sells a rebranded lens and does not want to tell
you what it is (which makes it harder to comparison shop, sort of like
buying a bed). But a rebranded lens that is purchased from a major lens
manufacturer is not the same as a proprietary lens.

Many of the so-called proprietary lenses fall into categories that are
similar to other lenses on the market, even if they are still under patent.
There are some exceptions such as Sola Spectralite, Trivex (Hoya Phoenix or
Younger Trilogy), and others. I assume that polycarbonate was at one time
proprietary, but probably the patent has expired.