Headaches: Why You Don’t Want To “Mix and Match” Prescriptions

You don’t want to use any random pair of old glasses you have laying around, to start on a project of using lowered prescriptions.  Things may not go perfectly, and you might not like the […]

Apr 17,2015 · 6 min read

You don’t want to use any random pair of old glasses you have laying around, to start on a project of using lowered prescriptions.  Things may not go perfectly, and you might not like the results!

I’m going to use Alex’ style for this post, referencing a recent forum post from Shannon.

quotesHi – I am just starting out, and have put my Snellen in my office, so that I can look there every 20 minutes and assess my vision. I check it in the morning. I was prescribed:

February 2015 Prescription (Age 29)
Right -9.0 / -1.0 x 175
Left -8.75 / -1.25 x 175

However, that was a breaking point for me, and refused to wear the glasses. The optometrist has my old glasses hostage at the lab, so I have been forced to wear these:

January 2009 Prescription (23 years old)
OD 8.0 -0.5 x 005
OS 7.5 -0.5 x 180

I have been wearing these for 6 days. Day one, huge headache. At first I would get tired eye muscles. Yesterday, no tired eyes at all. Today, on my 3M Snellen in daylight first thing int he morning I could read 20/20 with effort.

I have ordered 30 day disposables in -7.5, -7.0, -6.5, and -6.0. They just arrived yesterday, so I could use them.

I accidentally put the wrong lenses in my Zenni order, so had to order another pair that I can swap them out since they are in the wrong sides, so I will soon have two pairs:

OD -7.5 OS -7.25 and
OS 7.0 OS -7.75

I eliminated the astigmatism because I only developed it once I exceeded a -7.5 prescription.

I am thinking that since my prescription I had before the glasses I am currently wearing was -7.0 and -7.0 and that prior to this, my entire life my eyes were the same, that I will order a -6.5 and -6.5 pair.

My question from here is – what should I do in the meantime while I wait or my computer glasses? Should I wear the old glasses or contacts? I am in an office during the week editing video and designing. However, on weekends I go outside mostly all day now that it is warmer.

Secondly, do you think that I can go back to a same prescription in both eyes once I go down more steps? Like I said, my prescription prior to the one I am currently wearing was -7 both eyes and the same prior to that (Age 7-20)

Any feedback would be great. I believe I should hopefully improve quickly since I had tremendous computer eye strain due to my multimedia job and online masters. I have eliminated all screen time out of work hours and I have moved my computer further back until the computer glasses come in.



I’m posting this here in the blog since it is quite relevant to many first timers.  

Glasses prescriptions change the focal plane inside your eye.  They aren’t toys to be taken lightly, 
despite how your previous optometrist may have handled things (by overprescribing you).  Those focal plane changes can have very serious effects on your short term well being and long term vision health.

Everything from astigmatism to amblyopia, to retinal detachment can have a root somewhere in your perspiration history.

So when you change your prescription, do consider that they will affect your brain (which does all the interpreting of the signal from your eye).  And do realize that they will reshape your eye, in response to the change in focal plane.

Here is what I responded to Shannon in the forum:

quotes-bluePart of the headache is quite possibly the change in left vs. right eye strength, and the change in astigmatism correction. Most of the time just reducing prescription doesn’t cause much in terms of headaches. Fortunately though it seems as though you adjusted to it quickly.

A word of caution: You don’t want to be making too many changes to prescriptions, too often. Your brain has to do a lot of the hard work in figuring out the sudden and unexpected focal plane changes. It’s strenuous and not really helpful.

You will want to reduce your prescription complexity (less difference between left and right eye, less or no astigmatism correction). But often it makes sense to do it slowly and let everything adjust.

And whatever you do, have your distance correction and your close-up correction be the same in relative correction left and right eye.

For example:

Normalized (distance vision)

OD 8.0 -0.5 x 005
OS 7.5 -0.5 x 180 

Differential (close-up vision)

OD 7.0
OS 6.5

For close-up you very likely won’t need the astigmatism correction. If you don’t need it for distance either, all the better. But notice how the left and right eye have the relative same values, just a diopter lower for close-up.

Here too if you can do the same values for both eyes and get close to the same distance in centimeters, by all means. No need to force it, though.

And lastly, as the numbers go down, that half diopter between each eye represents a larger relative difference. At some point you will want to drop that to 0.25 diopters and eventually have them be the same.

This is quite the very long response, yet again.

Short version, wear what you have that doesn’t let you see too far but doesn’t give you a headache. For future reference, just wait for the right prescriptions, “mix and match” isn’t so great to avoid headaches. :-)

I hope that makes sense!  

You can find the whole thread here.

For the best experience, you want to take your centimeter results and current prescription into account.  When you have questions, just like Shannon did, post them in the forum.

You can get away with lots of things, because your vision system is quite amazingly resilient and adaptable to change.  But just like Shannon experienced with her headaches, some of the experiences are unnecessary.  Take your time, wait till prescriptions arrive, ask us in the forum, and have a smooth experience.

Although I have a feeling that Shannon will do quite well.  Those headaches are no fun and she didn’t write or complain, just stuck it out till everything adopted.  Not something you want to follow necessarily, but clearly Shannon is up for the task!

Take good care of your eyes,

– Neha


    Formerly genetically defective. 🤓 Weaned off retail optometry lens subscriptions, now 20/20 eyesight. Also into BJJ, kitesurfing, paragliding, being stupid.

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