Question about adjusting pupillary distance for different types of glasses

[Debbie Skolnik]

I know my distance PD (60).

I was told by a local optician, that because eyes converge when
looking closer up, an adjustment should be made when ordering reading
or computer glasses. She told me that for computer glasses, my PD
would decrease by 1.5, (58.5) and for reading glasses, another 1.5
(57).

Does this sound correct?

I want to make sure I take this into consideration when ordering
glasses other than for distance usage.

Thanks,

Debbie

[Beaugrand®™©]

That sounds about right, but usually PD is given in whole numbers. I
decrease my PD by 2 for computer glasses and 3 for reading glasses.

My "add" (I wear bifocals) is 2.00 for reading, and 1.50 works for
computer.

WHL

[Paul]

The "add" for computer glasses depends on your distance from the
screen.

[mitch]

Basic physics says that lenses focus
best if both eyes look through the exact optical centers, and
accurate PD's let you do this. Most people's pupils move
a bit inwards a mm or two when they look close (mine don't),
so there is no reason to assume your optician is wrong. They
get lots of practice, as they do this with every single customer.
If you don't trust yours to do something that common, you shouldn't
trust them to do anything.

BTW, if the part of your nose that the glasses rest on is off center,
you have two measurements, one from each pupil. Some glasses providers
can accomodate that, some can't.

It is not a difficult thing to measure - you can do it yourself in
near vision, and get a friend's help in far vision.

In addition, some lens suppliers can do it to .5 mm accuracy, some
only to 1 mm. I suppose that if you have a very strong prescription,
the difference might matter.