Re: Calculating Add for computer work

On Sat, 26 Jan 2008 08:57:19 -0600, "Mike Tyner" <mtyner@xxxxxxxxxxxxxx> wrote:


"Mark A" <nobody@xxxxxxxxxxx> wrote

If you look at Zeiss informational material (or any other vendor who sells
computer glasses) they are quite clear (no pun intended) that computer
glasses are not for driving (because the lens does not contain a viewing
area with your distance Rx).

I'm sure you're right about what it says, but a half diopter of blur doesn't
normally reduce vision to 20/40, even at night, so there are people driving
lawfully with worse vision than you get from a little extra plus.

True, but a half diopter is a room distance lens, not a computer lens. Or as Jon
Stewart might say, it's more like a gratuity, and a cheap one at that.

Kidding aside, the "office" type lenses made by Zeiss and other companies put
about 50% to 70% of the Add on the distance gaze. Because I don't start
thinking about computer glasses until the Add is above +1.75 (assuming typical
work distances and healthy eyes), that places anywhere from one, to as much as
one and a half diopters of plus on the distance, more than enough to cause
blurring of road signs and other distance objects.

To the OP:

If the +1.00 Add was for about 40cm, then you should have enough reserve
accommodation to see the screen comfortably and clearly at 70cm when you look
through the distance portion of the glasses, or without glasses if there is no
distance Rx, sans accommodative or vergence dysfunctions.

IMO there's more danger in those 1/2-inch "fashion" temples that California
outlawed in 1959.

-MT

I didn't know that. Most folks don't seem to ever look in their mirrors anyways.

In Texas, you can keep a loaded gun under the seat or in your pocket, pull up to
a drive up window and buy a bottle of Jack, and until a few years ago, you could
drink it and drive, as long as you were not "impaired".

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

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