Request for advice with mid distance lens problem

[highstream]

I recently opted for a pair of Shamir Autograph II to fit in a 33 mm
(B) frame, after years of using Varilux Comforts (CR39) in a 31 mm
(B) frame. Between the prescription, opticians and lab, it took two
eye exams, two fittings and three pairs of lenses before they got
everything right, at least per the numbers. While there are things
much to like about these lenses, there is one overriding problem. The
area that falls in 'mid distance' is blurry. That's from about 20"
out to about at least 5 feet, getting worse as it goes out. That
includes practical vision areas like the computer screen (33-36") and
viewing titles in the library stacks. Just the sort of 'gap' that
creates an everyday problem. It was even worse at first, going well
into normal reading distance (15-18"),* but the optician ended up
leaving aside the fit and pulling the nose pads back so the fame sits
directly on my nose and thus reading area is more accessible. This
has all come as a surprise, because this wasn't a problem with the
previous Comforts (or earlier Shamirs misfitted at 21 mm). The
optician's solution is computer glasses. I wonder...

My first question is: Is this problem primarily a function of the
change of prescription (my eyes) or more of the nature of the Shamir
lens relative to this frame's vertical? The Shamir requires a minimum
19mm fit, mine being fit at 19.5mm. Would I have been better off with
something requiring a shorter fit? When I initially mentioned the
Autograph IIs, the shop suggested the Zeiss individual, which requires
an 18mm minimum (they had done Autographs, but this was their first
pair of IIs, and it required using a different lab than they normally
use and prefer). Thanks.

Rx (for Comforts):
OD +0.25 -0.75 100 +2.00
OS +0.50 -1.50 90 +2.00

Current Rx (for Autograph II):
OD +0.25 -0.75 90 +2.25
OS +0.50 -1.00 100 +2.25

* The main reason for the follow up eye exam was that the original
prescription set up a reading distance of a foot, really 9", which
this shop considers normal. They do not recognize how close a foot
actually is, and how relatively unusual it is for anyone short of
thick lenses to hold material that close.

[Chuck Knight]

Are the glasses sharp at *any* mid distance, regardless of the
position in the lens?

-- Chuck Knight

P.S. Why did you change lens type? From your description, it sounds
like the Varilux worked well for you.

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[powrwrap]

On Dec 25, 5:23 pm, highstream <geneg...@peoplepc.com> wrote:
>  While there are things
> much to like about these lenses, there is one overriding problem.  The
> area that falls in 'mid distance' is blurry.  That's from about 20"
> out to about at least 5 feet, getting worse as it goes out.  That
> includes practical vision areas like the computer screen (33-36") and
> viewing titles in the library stacks.  Just the sort of 'gap' that
> creates an everyday problem.  

We have a very similar problem. If I want to see anything clearly from
about 18" to about 4 feet away, best thing is to remove my glasses.
Yes, I can tilt my head and find a very narrow sweet spot where things
are relatively sharp but it's like looking through a gun slit window
on an armored vehicle.

> My first question is: Is this problem primarily a function of the
> change of prescription (my eyes) or more of the nature of the Shamir
> lens relative to this frame's vertical?  

I'm going to guess the Shamir lenses are the culprit. Your
prescription hasn't changed at all for distance and just a tad for
reading.

[highstream]

Assuming what's being read is lower than eye height, the Shamirs are
sharper out to reading distance, 18" or so, about even to 24", but
past that, out to at least 8', not as clear as the Varilux pair.
Depending on the angle of viewing and distance, raising my head tilt
sometimes helps. I've also been wondering if the Varilux pair's AR
has a little darker tint than the Shamir's Avance, with the greater
contrast making things appear a bit clearer than the prescription
difference itself would suggest (the Varilux came from a very good
shop, but they didn't record or recall which mid-priced AR would have
been used). The Shamir lenses were de-polished (?) to lessen overhead
light streaking - and light sensitivity generally? - but they still
get a bit of streaking in some rooms, depending on the lighting.

After 10 years with Comforts, inclduing four years with this last
pair, I figured with a change of frames it was worth a look at the
alternatives was worth it, especially since lens design quality has
improved so much over the years (i.e., not just marketing). Reading
through a pro's forum, the phrase "best I've ever used" kept coming up
for the Autograph IIs, which is what took me in that direction, for
better and worse. I can still return the Shamir pair and, after Jan
1, the optician can probably get a coupon for the Zeiss individual.
The question is, would that make any difference in terms of mid
distance viewing (without introducing other problems)?