New lenses are odd...

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jack - 21 Oct 2008 20:54 GMT

I lost my glasses and got a new pair.
Comparing them to my safety glasses of the same prescription, I find the new
glasses are clearer both reading and driving; so overall I like them.
But... when I look down at my dinner plate, it looks like it is tilted away
from me because the nearest part is noticably more magnified than the top.
(so it seems nearer than it is... tilted away from me). My safety glasses
don't do this at all.

The safety glasses are polycarbonate; the new glasses are trivex.

Is one prescription wrong, does the different material do it, or maybe it is
just an idiosycracy of one of the lense designs. What do you think?

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Mike Tyner - 21 Oct 2008 23:11 GMT

> Comparing them to my safety glasses of the same prescription, I find the
> new glasses are clearer both reading and driving; so overall I like them.

How does that work.. the new pair is clearer but the prescription is the
same?

> But... when I look down at my dinner plate, it looks like it is tilted
> away from me because the nearest part is noticably more magnified than the
> top. (so it seems nearer than it is... tilted away from me). My safety
> glasses don't do this at all.

The sense of trapezoid-shaped distortion is pretty common and usually goes
away.

Every lens creates distortions, and almost everybody "gets used to" the
effect of a certain prescription in a certain frame. Meaning you
subconsciously adjust to a new idea of what is straight, or level, or
square.

Even with "identical" prescriptions, shape distortions change when you
change the angle, thickness, size and/or shape of the new lenses. Most of
these changes are dictated by your choice of frame.

> The safety glasses are polycarbonate; the new glasses are trivex.

Changing back to poly will not automatically fix the problem, especially if
the new frame is substantially different from the old one.

In the case of trapezoids, it's often that your old lenses were centered
significantly higher or lower. Or the frame might put your new lenses at a
different angle (pantoscopic tilt), or distance off your eye.

The trapezoid may change or even disappear when you wear your glasses too
high or too low, or tilt them closer in toward your cheeks.

In general, frames that are smaller, rounder, and fit more close to the eyes
will distort less than large, square frames sitting out off the eyes.

> Is one prescription wrong, does the different material do it, or maybe it
> is just an idiosycracy of one of the lense designs. What do you think?

It's a good bet your new frame is somehow different. If it's a couple weeks
and you can't get used to it, consider exchanging the frame.

-MT

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Mark A - 22 Oct 2008 03:55 GMT

>I lost my glasses and got a new pair.
> Comparing them to my safety glasses of the same prescription, I find the
[quoted text clipped - 8 lines]
> Is one prescription wrong, does the different material do it, or maybe it
> is just an idiosycracy of one of the lense designs. What do you think?

Most likely the new lenses are aspheric and the old ones where spherical. An
aspheric lens has many advantages for a high power Rx (thinner and lighter),
but it is sensitive to the optical center of the lens being positioned
exactly where your pupil is located.

Both polycarb and Trivex are safety lenses because they have very high
tensile strength and impact resistance.

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Robert Martellaro - 23 Oct 2008 22:09 GMT

>I lost my glasses and got a new pair.
>Comparing them to my safety glasses of the same prescription, I find the new
[quoted text clipped - 8 lines]
>Is one prescription wrong, does the different material do it, or maybe it is
>just an idiosycracy of one of the lense designs. What do you think?

The lenses may not be positioned in front of the eyes correctly. There may be
other errors. Inform your optician of the problem- it shouldn't take more than
five minutes to troubleshoot this.

Hope this helps

Robert Martellaro
~~~~~~~~~~~~~~~~~~
Optician/Owner
Roberts Optical
Wauwatosa Wi.
~~~~~~~~~~~~~~~~~~
"Science is a way of trying not to fool yourself."
- Richard Feynman

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