# Optical Forums > General Optics and Eyecare Discussion Forum >  Base curve in eyeglass prescription

## catopounce

I recently had some eyeglasses made and while wearing them for two weeks I experienced constant headaches. I went to my Optometrist (not where I got the glasses) and he said that I needed a base curve of +3.75 in each lens. The lenses of these new glasses were much flatter---base curve of +2.25 and +1.50. I'm having the glasses redone for free, but my question is: Should this base curve have been specified in my prescription, or should the optician who dispensed the specs have measured the base curve in my current glasses in order that the new ones to be the same? This has never come up before, I've worn corrective lenses for 25 years. Also, the base curve was different in each new lens, was that a mistake? Thanks!

My Rx is :
OD -5.75  -1.00 005     OS -6.00 -0.75  180    add +1.25 in both

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## AWTECH

Your prescription indicates the same total power in each eye.  That is the sph -5.75 added to the cyl - 1.00= -6.75 total for the right eye.

The left eyw is sph -6.00 added to the cyl -.75 = -6.75  

The same base curve would have been appropriate in my opinon.  However there are many aspects to your new Rx size of frame, material of the lens etc. to consider.  The end result should be that you can see without getting headaches.  It also sounds like they are making good on remaking them.  Hopefully they will get it so that you do not continue to have any problems, and can see perfectly without headaches.  It could have been a simple mistake during processing of the prescription.

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## OPTIDONN

I am wondering about your Dr's base curve findings. There are several factors he may not have considered. Is the lens aspheric? If so this could acount for the difference between the right and left base curves. Checking an aspheric away from its central portion will give you a bit of an inacurate reading. What is the index of your lenses? A higher index lens does not require as much curvature as a lower index lens. A 6 base in 1.498 index will be steeper than a 6 base in a 1.67. The lens measure used to check base curves is calibrated to 1.50 (or 1.523 I forget). If you use a lens measure to check a lenses base curve it will tell you the refractive power at lens measures index not the actual lenses. I think that the lenses may have been done on the correct base curves they just may have been checked incorrectly.

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## catopounce

> I am wondering about your Dr's base curve findings. There are several factors he may not have considered. Is the lens aspheric? If so this could acount for the difference between the right and left base curves. Checking an aspheric away from its central portion will give you a bit of an inacurate reading. What is the index of your lenses? A higher index lens does not require as much curvature as a lower index lens. A 6 base in 1.498 index will be steeper than a 6 base in a 1.67. The lens measure used to check base curves is calibrated to 1.50 (or 1.523 I forget). If you use a lens measure to check a lenses base curve it will tell you the refractive power at lens measures index not the actual lenses. I think that the lenses may have been done on the correct base curves they just may have been checked incorrectly.


Thank you very much for your replies here. Regarding your first point, the optician at my doc's office was the first to measure the differences in the base curves of the old vs new lenses.

 I guess the plot thickens here...well, I'll get my new glasses after Christmas, I hope they're right, and no constant headache! (not fun)  Also, the old lenses are progressives, the new weren't, but my eye doc and two opticians at his office swore up and down that the base curve in the new lenses ought to be +3.75. As I said, I've owned several pairs of specs in 25 years, and this has never come up. But, my current glasses are progressives...(love 'em!)
 :)

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## Chris Ryser

> My Rx is :
> *OD -5.75 -1.00 005 OS -6.00 -0.75 180 add +1.25 in both*


The base curve in myops should ne copied, even if it should be slightly different by the book. Myops having worn lenses with a vertain base curves have gotten used to it and have often a hard time adapting to something else.

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## Leo Hadley Jr

I think a +3.75 BC is pretty steep for -6.00-75 RX. I wonder why the Doctor and Optician are insisting on that.

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## QDO1

there is more than the base curve going on here.  with a 1.25 add you are a new(ish) presbyope.. i bet the progressive design and fitting measurements have more to do with your problem than the base curve

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## Chris Ryser

> *there is more than the base curve going on here. with a 1.25 add you are a new(ish) presbyope.. i bet the progressive design and fitting measurements have more to do with your problem than the base curve*


.......of course youii might have a point there too...........there is 60% of distortion on that lens........or as Darryl calls it diplomatically "surface astigmatism"..............which is not going to help.

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## QDO1

> .......of course youii might have a point there too...........there is 60% of distortion on that lens........or as Darryl calls it diplomatically "surface astigmatism"..............which is not going to help.


if you want to be picky - all lenses distort light - thats the function of them.  the thing is to decide what distortion you want

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## catopounce

All I know is that the new glasses (*aren't*  progressives) gave me a continuous headache for two weeks until I stopped wearing them. (My "old" glasses *are* progressives) I thought I could tough it out and that the headache would go away, but it didn't. 
:hammer: 

The new frames are smaller and rectangular, the "old" fames are larger ovals. With the new glasses the vision was great, and for reading I just held the book farther away. (Maybe the fact that the new ones weren't progressive was causing the headache.)

The new lenses will be Varilux Ellipse.

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## QDO1

> All I know is that the new glasses (*aren't* progressives) gave me a continuous headache for two weeks until I stopped wearing them. (My "old" glasses *are* progressives) I thought I could tough it out and that the headache would go away, but it didn't. 
> :hammer: 
> 
> The new frames are smaller and rectangular, the "old" fames are larger ovals. With the new glasses the vision was great, and for reading I just held the book farther away. (Maybe the fact that the new ones weren't progressive was causing the headache.)
> 
> The new lenses will be Varilux Ellipse.


sounds like you worked the problem out allready! :cheers:

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## catopounce

> sounds like you worked the problem out allready! :cheers:


It seems obvious that it was the absence of progressive lenses was the problem with the new lenses, but my Eye doc didn't say that, nor did the two opticians at his office.   :Confused:

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## Matthew

With the power stated a 2 base curve is not by any means ot of the question.

I would think that a 4 curve might be a forced curve with the power you stated.

I dont know why you had 2 curves with a similarly powered lenses.  But different curves do not describe your symptoms.

My guess is your base curve is not the problem.

Have your lenses verified by another doctor/Optician

Have them check your pupilary measurement. Also check to make sure the optical centers are in alignment, if they are not you can have unwanted prism.

It possibly might be lens material, but more likely You need a second opinion with your refraction.

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## Robert Martellaro

> but my question is: Should this base curve have been specified in my prescription, or should the optician who dispensed the specs have measured the base curve in my current glasses in order that the new ones to be the same?


None of the above. The lab and lens manufacturer should determine the correct BC for any given power and lens design combination. To do otherwise, with few exceptions, will result in a thicker lens with decreased off-axis performance. 

Hope this helps,

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## QDO1

> None of the above. The lab and lens manufacturer should determine the correct BC for any given power and lens design combination. To do otherwise, with few exceptions, will result in a thicker lens with decreased off-axis performance. 
> 
> Hope this helps,


although this is the normal scenario, any dispensing optician worth his salt, measures old base curves, and might alsospecify a base curve, knowing the implications of what he is doing

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## Matthew

> None of the above. The lab and lens manufacturer should determine the correct BC for any given power and lens design combination. To do otherwise, with few exceptions, will result in a thicker lens with decreased off-axis performance. 
> 
> Hope this helps,


While that is the optimal choice to let your lab pick the base curve. Not all labs pick the right curve. They can force a curve if say......they dont have the one they need in stock. :finger:  Creating exactly your comment unwanted effects.

Thats when I call them back and make them do it right, asking them what does the manufacturer suggest on this.

Opticians should have good knowledge of Base curves and ocular curves relating to lense materials and work shoulder to shoulder with a quality lab.:cheers:

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## Robert Martellaro

> While that is the optimal choice to let your lab pick the base curve. Not all labs pick the right curve.


In that case, they're fired. 




> Opticians should have good knowledge of Base curves and ocular curves relating to lense materials and work shoulder to shoulder with a quality lab.


Agreed. To keep it simple, I just tell the lab to use "best form" BCs, and to call me if there is a problem. 

Regards,

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## catopounce

> although this is the normal scenario, any dispensing optician worth his salt, measures old base curves, and might alsospecify a base curve, knowing the implications of what he is doing


This is what my Optometrist implied, but I'm certainly getting a lot of different opinions here. 
He didn't say anything about the new glasses NOT being progressives while my old/current ones ARE progressives being the problem.

Athough he originally stated that PAL +1.25 was "optional", as far as I'm concerned, it is not.

I've had many different eyeglasses in 25 years and this has never arisen, which makes me wonder if the lack of Progressives in the new lenses was the real headache cause. I will get the specs after Xmas and let you all know.

PS: I hate to bash Costco, because it's a great store and the staff are treated well, but this problem is one of three I'm afraid I've had with these specs from their Optical dept.

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## HarryChiling

I would suggest that you stick with your doctors opinion on the matter, after all we all should only be going to doctors we can trust.  The fact that the lenses were on 2 different base curves is not uncommon.  As much as you will hear best form and suggestions about base curves, if you were to walk into my dispensary I would use a stock lens for both eyes since they do fall within stock range.  By using stock lenses I would eliminate haveing to surface lenses for a simple Rx, however if I was to measure a base curve and it was something that would not be common then Iwould consider matching the base curve.  Usually if I do match the curve and it is a curve that I feel does not make the best lens, my goal would be to try and split the difference or at least slowly wean you away from the wrong curve.

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## mullo

Just curious as to which location you bought them at and what the other 2 problems were? 


> This is what my Optometrist implied, but I'm certainly getting a lot of different opinions here. 
> He didn't say anything about the new glasses NOT being progressives while my old/current ones ARE progressives being the problem.
> 
> Athough he originally stated that PAL +1.25 was "optional", as far as I'm concerned, it is not.
> 
> I've had many different eyeglasses in 25 years and this has never arisen, which makes me wonder if the lack of Progressives in the new lenses was the real headache cause. I will get the specs after Xmas and let you all know.
> 
> PS: I hate to bash Costco, because it's a great store and the staff are treated well, but this problem is one of three I'm afraid I've had with these specs from their Optical dept.

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## catopounce

Does anyone think that the *switch* from Progressives +1.25 ("old" glasses) to new single-vision is causing the headaches? 

I just picked up *another* pair of glasses, (ordered before I had headache problem) rimless, with this new single-vision Rx and the headache is there too. Don't know what the base curve on these lenses are.

Will pick up redone glasses with 3.75 base curve AND Progressive lenses on Monday.

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## William Stacy O.D.

> Does anyone think that the *switch* from Progressives +1.25 ("old" glasses) to new single-vision is causing the headaches? 
> 
> I just picked up *another* pair of glasses, (ordered before I had headache problem) rimless, with this new single-vision Rx and the headache is there too. Don't know what the base curve on these lenses are.
> 
> Will pick up redone glasses with 3.75 base curve AND Progressive lenses on Monday.


Depends on what the SV Rx was.  If it was for near only (calculated from the original Rx plus the add) readers, it shouldn't cause HAs.  If it were the distance only, it might, because you'd be trying to read (at least part of the time) with the full distance Rx.  Unequal base curves on lenses that are essentially the same power can indeed cause HAs (induced aniseikonia), and can cure HAs that are CAUSED by aniseikonia (RARE). If inadvertent or non-prescribed, it was a definite :finger:

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## catopounce

Dr Stacy: Thank you. Another thing, my "old" progressive glasses are indeed *glass lenses*. I have another pair of *glass* single-vision glasses that I used to switch off from my "old" progressives, and there was no headache. They were small rectangular lenses.

Sort of going crazy... :hammer: Hoping re-dos will solve problem.

NEW RX    OD  -5.75  -1.00  005          This is on both pairs of "HA" specs.
               OS  -6.00  -0.75  180

"OLD" RX not known, but had +1.25 add in both lenses.

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## Andrew Weiss

Dear Catopounce,

You have a lot of different things going on here:
-- lens type (SV versus progressive)
-- lens material (glass versus others)
-- different base curves (more on that later)
-- different frame configurations
-- maybe even variations in interpupilary distance (PD), vertex distance, frame wrap, and other factors

Some people are more sensitive to change than others, and some are more sensitive to changes in certain things --like lens materials, or base curves -- than others.  Most people will not notice any significant difference visually between glass and plastic, or between a lens ground on a 2.0 base and one ground on a 3.5 base.  However, there are some who do.  And for those folks, we opticians have learned to be more careful.

To trouble-shoot down a problem like the one you're having can require a fair amount of knowlege, experience and patience.   And to do it by remote control, as we are doing here, is even more challenging.  Personally, I like to see the patient and the glasses (and the old glasses!).

That said, based on the information you've shared, I'd agree with you and with QDO1 that the most likely culprit is your change from progressives to SV lenses.  You are probably trying to read with those lenses, and see intermediate objects, and therefore straining your eyes somewhat.  Going from multifocals back to single-vision can produce this problem.

Now, to answer your original question :hammer:

Our doctors will specify base curves with patients who have a significant degree of astigmatism.  Their desire is to keep the patient in a lens with a front curve similar to what they've worn in the past, on the theory that it will make an easier adaptation to the distortion caused by the astigmatic correction.  I would say that this does not apply in your case.

I wish you the best and a happier, more headache-free, new year.

Andrew.

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## catopounce

Hi Andrew: Thank you for your comprehensive answer!

My eye doc didn't say much about the change to single vision with the new glasses, and he had said on my Rx that it was "optional". (+1.25) On the recent visit though, he rewrote my Rx with "needs PAL  +1.25" and "needs base curve 3.75." So, he changed "optional add +1.25" to "mandatory." 

I will have to change other new glasses to Progressive.( $)

And yes, you are right, you can't solve my problem by "remote control"!

Thanks for your very informative and helpful post and good wishes and Happy New Year to you too!
 :cheers:

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## Happylady

Are you SURE your other glasses are glass lenses? It is extremely rare to use glass lenses witha prescription as strong as yours.

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## catopounce

> Are you SURE your other glasses are glass lenses? It is extremely rare to use glass lenses witha prescription as strong as yours.



Yes, other glasses were definitely glass, but Rx was in 2003, may have been -4.75.

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## catopounce

Well, if anyone is interested I picked up my re-done eyeglasses, now with +3.75 bases curve in each lens and PAL +1.25.  SO FAR, NO HA (headache)

Interestingly though, today I also picked up a second pair of new glasses, ordered before HA problem occurred with the other pair, and these too have no PAL. No headache so far with these, either! 

So, don't know exactly what the problem was with those other ones. 

Anyway, what a relief.  Thanks for all your input here.  :cheers:

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## catopounce

Headache with online glasses single vision, unknown lenses.

Headache with Crizal Alize 1.67 lenses. (aspheric?)



No headache with Sola Vizio 1.67 aspheric/atoric.

No headache with Essilor Ellipse 1.67, PAL +1.25, +3.75 base curve.

Conclusion: Must have Vizio aspheric/atoric lenses or +3.75 base curve in other lenses.

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