Reasonable prices for great glasses

This is what I was told by someone who works for Essilor, who is in
charge of their coating lab here in Dallas. He said that the results
of their marketing were that preference was shown for the colorized
product, and so they never marketed the colorless version.

Believe it, or not.

DrG

 

"Colorless" with respect to A/R is most likely a relative term. The
fact is they can alter the color balance.

DrG

 

I'll join in here with a "ditto". Polycarb is best used as a packaging
material or aircraft window (for which it was originally designed and
intended), not for ophthalmic lenses except when there is no other
alternative. I don't think I've dispensed but a handful of polys in the
last 5 years since Trivex and other high-index, low specific gravity
materials "matured" into use.

Shamir's Genesis and Piccolo and Hoya's Trivex PALS are not just
"premium" in my office, but the "standard of care".

LB, O.D.

 

OK I've been bashing poly for a long time, but I must say they
occasionally have a place in addition to helmet visors and what not.
For example, a +1.00 or -1.00 where safety and cost are prime factors.
Esp. if they want dead white (no color) in the lens. The chromabbs will
be pretty minimal in low Rxs. But I'm for Trivex in most Rxs under 4 D.

C'mon Hoya, are you listening? Bring on a Trivex version of Tact! Please

w.stacy, o.d.

 

I'm with mike on this one. There is no colorless AR coating, since they
all have to select a wavelength or two to reflect, and the reflection
will have the color(so) of the wavelength that is reflected. For the
reflected light to be colorless (white), it would have to reflect all
wavelenghts pretty much equally. The only lens that does that is an
UNCOATED lens.

w.stacy, o.d.

 

I appears as though I have a choice to believe you or the guy whom I
have known for many years and who has spent most of his professional
career developing coatings. I'll have to give this some deep thought.

DrG

 

(anti-reflective coatings)

Reflections from the surfaces of my $29 Zenni's have got a
green-looking dichroic sheen. Reminding very much of
what one gets from an A-R coating. As these are rimless
and inexpensive, they must be of polycarbonate. I did not
request coating.

Considering what has been said here, one must wonder how
Zenni could provide A-R coatings in such inexpensive eye
glasses.

Well, one thing -- slight blemishes in the coating are beginning
to show in the coatings around the bridge screws. Possibly the
glasses will need to be replaced after a year or so.

Since these are reading glasses, I don't know why they should
be A-R coated. My question to Zenni would be: could the
eyeglasses be supplied without the coating. Maybe I should ask
for my money back on the first pair, since I did not want them
coated.

 

Stock lenses are available with coating. The better coatings don't
chip, and will resist scratches. It's a different ball game when the
lens has to be surfaced, as is the case for higher prescriptions and
multifocals, and the coating has to be applied afterwards thereby
diminishing the economy of scale.

DrG

 

OK it would be THEORETICALLY possible to construct a multi-layer of 3
coatings, one for each of the primary color wavelengths, each layer with
appropriate indices of refractions and thickness appropriate for it's
substrate (being the underlying lens or the next layer "down" in the
stack. I do know that no such coatings are commerically available for
glass or plastic, if they ever existed at all.

w.stacy, o.d.

 

One more thought. Even if you got a perfect result with the above, most
ambient light has many wavelengths in addition to those of the primary
colors. Those wavelengths would be reflected much more strongly than
those of the primaries, so the resultant reflections would necessarily
have color. E.g. say at sunset, the orange sunlight would reflect
orange off the "colorless" coating. Colorless under lab conditions only
I'm afraid...

w.stacy, o.d.

 

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