> "Horus" <horus...[at]hotmail.com> wrote
> > right and -8.0 diopter lens left that uses computer a lot. Does it
> > make sense to get a 65 (corrected for near) pair rather than
> > corrected for far (68) if my PD is 68?
> I'm pretty sure you couldn't tell the difference.

> Your glasses (pd 68) provide about 2.5 prism diopters of "assistance" when
> you converge to a PD of 65.
> Remaking them with a PD of 65 would eliminate that assistance and require
> you to converge _more._

> > I don't understand. My PD is 68. If I get a pair with optical centers
> > of
> > 66. This means my eyes are looking thru the optical centers when
> > seeing near. Convergence will be normal. But if I use a pair with
> > optical centers same as my PD. There will be less convergence
> > demand due to the base-in as you stated. Isn't this the important
> > reason why glasses are corrected for distance (meaning the PD
> > matches the optical centers) in order to make you more relax
> > even if you will use the minus lens exclusively for near??
> I don't think it's done for that reason. If you're farsighted, the same
> conventions work _against_ you.
> > What I meant by distortion is not seeing directly at the optical
> > centers but sideways (or base in).
> Regardless of centration and prism, there is huge barrel distortion at -700
> or -800. Moving the OCs only moves the center of the "barrel" a little left
> or right. Doesn't reduce it at all.

> -MT

> On Mar 18, 9:48*pm, "Mike Tyner" <mty...[at]mindspring.com> wrote:
> > "Horus" <horus...[at]hotmail.com> wrote
> > > > In prescribing glasses for myopes. The prescription says corrected
> > > for distance and not near.
> > > I don't understand. Is there some checkbox, or other indication that your
> > glasses are not corrected for near?
> What I meant to say is this. My PD is 68. The glasses optical centers
> are also 68 (meaning corrected for distance although one can still
> focus near of course). Now corrected for near means the optical
> centers are 68-2=66 or 65. For Myopes with -7.0 diopter lens
> right and -8.0 diopter lens left that uses computer a lot. Does it
> make sense to get a 65 (corrected for near) pair rather than
> corrected for far (68) if my PD is 68?

> right and -8.0 diopter lens left that uses computer a lot. Does it
> make sense to get a 65 (corrected for near) pair rather than
> corrected for far (68) if my PD is 68?

> I don't understand. My PD is 68. If I get a pair with optical centers
> of
> 66. This means my eyes are looking thru the optical centers when
> seeing near. Convergence will be normal. But if I use a pair with
> optical centers same as my PD. There will be less convergence
> demand due to the base-in as you stated. Isn't this the important
> reason why glasses are corrected for distance (meaning the PD
> matches the optical centers) in order to make you more relax
> even if you will use the minus lens exclusively for near??

> What I meant by distortion is not seeing directly at the optical
> centers but sideways (or base in).

> "Horus" <horus...[at]hotmail.com> wrote
> > In prescribing glasses for myopes. The prescription says corrected
> > for distance and not near.
> I don't understand. Is there some checkbox, or other indication that your
> glasses are not corrected for near?

> > The reason being that when corrected
> > for distance, there is less convergence needed when viewing
> > near.
> I didn't know that. My prescriptions don't specify convergence.
> > Isn't there any side effect for getting less convergence
> > compared to natural.
> -7.00 glasses assist near convergence automatically. When the glasses are
> made for a 64 pupil distance and you converge, your actual pupil distance
> becomes 60 or 61 and there is a tiny amount of base-in prism induced by
> decentration.
> > Is the relaxation that one gets for reduce
> > convergence significant? It really gives you less strain?
> Not normally.
> If you have an insufficiency of convergence ability or some other binocular
> disorder, it could be "less straining." In normal, healthy eyes it would be
> difficult to tell any difference.
> > I'm
> > 29 years old and use computer 15 hours a day. I plan to get
> > a duplicate pair of glasses with same -7.0 diopters but corrected
> > for near to be free of glasses distortion
> I don't think you'll gain much from changing the pupil distance, if both
> pairs are -7.00.
> In most cases, "reducing strain" indicates reducing accommodation.
> Accommodating stimulates convergence and it will still continue to do so if
> you make new glasses.
> So you risk tipping over into convergence excess, rather than convergence
> insufficiency.

> > but I won't be able to get
> > the advantage of the glasses corrected for distance which is
> > reduced convergence.
> Reducing convergence will have no net effect on "distortion" in -7.00
> glasses.

> > *What would you rather have, less
> > distortion (corrected at near) or reduced convergence
> > (corrected at distance) assuming you are a young myope?
> > Hope someone can clear this up.
> The problem is you're overthinking.
> -MT

> In prescribing glasses for myopes. The prescription says corrected
> for distance and not near.

> The reason being that when corrected
> for distance, there is less convergence needed when viewing
> near.

> Isn't there any side effect for getting less convergence
> compared to natural.

> Is the relaxation that one gets for reduce
> convergence significant? It really gives you less strain?

> I'm
> 29 years old and use computer 15 hours a day. I plan to get
> a duplicate pair of glasses with same -7.0 diopters but corrected
> for near to be free of glasses distortion

> but I won't be able to get
> the advantage of the glasses corrected for distance which is
> reduced convergence.

> What would you rather have, less
> distortion (corrected at near) or reduced convergence
> (corrected at distance) assuming you are a young myope?
> Hope someone can clear this up.