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Home > Archive > Vision > April 2005 > Lens Material - Again
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Lens Material - Again
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| Stan Smiley via MedKB.com 2005-04-27, 5:57 pm |
| sphere/cyl/axis
-5.25 -.50 50
-5.25 -.75 105
Went with Pentax 1.67 (vanity!), but now struggling to focus with indoor
lighting and mid distance objects (3-25 ft.) found in an office setting.
Outdoor distance vision and reading seem decent, but the “sweet spot”
peripherally seems even slimmer than my older polycarb lenses. Lens and
perscription have been double checked. Can chromatic aberration be coming
into play?
Better suggestions on lens material (brands) for a remake?
Thanks, Stan
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Message posted via http://www.medkb.com
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| Mark A 2005-04-27, 5:57 pm |
| "Stan Smiley via MedKB.com" <forum@nospam.MedKB.com> wrote in message
news:7203d0a84af64acf8b98b455387ebc48@MedKB.com...
> sphere/cyl/axis
> -5.25 -.50 50
> -5.25 -.75 105
>
> Went with Pentax 1.67 (vanity!), but now struggling to focus with indoor
> lighting and mid distance objects (3-25 ft.) found in an office setting.
> Outdoor distance vision and reading seem decent, but the "sweet spot"
> peripherally seems even slimmer than my older polycarb lenses. Lens and
> perscription have been double checked. Can chromatic aberration be coming
> into play?
>
> Better suggestions on lens material (brands) for a remake?
>
> Thanks, Stan
>
Can you see better if you move your frame around on your face? This would be
an indication of a poor fitting (fitting height/PD not measured properly or
lens not placed properly in the frame). Also, try one eye at a time.
Also, do you have Proceed or Proceed II Short model of lens? Is you Rx
stronger than before? (this exaggerates distortion problems, especially if
the add power is stronger).
You didn't say what your old lens design was (manufacturer and model). For
example, Varilux Panamic or Rodenstock Multigressiv2, etc.
Polycarb has an abbe value of 30, and Seiko 1.67 has an abbe value of 32
(slightly better).
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| Robert Martellaro 2005-04-27, 5:57 pm |
| On Thu, 21 Apr 2005 07:58:54 GMT, "Stan Smiley via MedKB.com"
<forum@nospam.MedKB.com> wrote:
>sphere/cyl/axis
>-5.25 -.50 50
>-5.25 -.75 105
>
>Went with Pentax 1.67 (vanity!), but now struggling to focus with indoor
>lighting and mid distance objects (3-25 ft.) found in an office setting.
>Outdoor distance vision and reading seem decent, but the “sweet spot”
>peripherally seems even slimmer than my older polycarb lenses. Lens and
>perscription have been double checked. Can chromatic aberration be coming
>into play?
>
>Better suggestions on lens material (brands) for a remake?
>
>Thanks, Stan
Stan,
Problems with office lighting could be due to the absence of an anti-reflection
coating.
Incorrect lens positioning will reduce acuity at all distances, on-axis or
off-axis, for reasons unrelated to transverse chromatic aberration. So changing
the lens material will not necessarily improve the vision.
Since the Rx and lens powers have already been checked, it's now time to measure
the vertical and horizontal monocular PDs (distance between pupils), vertex
distance (eye to lens), panto (lens tilt), and BC (front lens curve).
My guess is that the vertical OCs are too low with the lenses resting too far
from the eyes.
Hope this helps,
Robert Martellaro
~~~~~~~~~~~~~~~~~~
Optician/Owner
Roberts Optical
robopt@execpc.com
~~~~~~~~~~~~~~~~~~
"An expert is a person who has made all the mistakes that can be made in a very narrow field."
- Niels Bohr
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