Figuring out differentials

hey jake , i also sent my problem to you on email. but got a reply with ‘it’s awesome’. i hope , telling here will resolve it.
today i read , differential glasses topic on le rough guide , and i learned a lot. and now i have two you told in guide… basically i need you help and support.

option 1. i got my eyes checked two weeks before(computerized eye checking) the results were left= -3.25 , right=-3.00 . my question is = is there any chance that the computer eye checked is wrong or the prescription given me can be wrong?

let’s suppose the prescriptions are right , so as you said substract , +1.50 . from each eye. this is your differentials diopters . so accordingly . my differentials should be , left= -1.75 , right= -1.50 . ok good.
but i am using contacts . so i’ll wear differentials over lenses. whole day.
so what about the blur challenge when i’ll be not doing any close up? because with left= -3.25 , right= -3.00. there will be no blur challenge for me when i’ll outside.

option 2 . according to my snellen and centimetre measurements .
in morning(no close up , at 6am after yoga) , left= 39 , right = 43
in evening(lotsa close up , but ya i do started appyling 20/20/20rule)= left= 33 , right= 37.

please suggest me guru , what should i choose?

note= i do not feel comfortable(blur thing, feels so high) with my contacts , with my recent opto prescription , left = -3.25 , right= - 3.00.
so they provided me contact lenses with , left= 3.00 right = - 2.75

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What can you read on a Snellen chart with your opto prescription at good lights?
What can you read with left = -3.25 , right= - 3.00 I assume you have glasses with this?
vs. contacts left= -3.00 right = - 2.75?

As for the centimeter drop: it is normal, close up can make your eyes and brain tired by the end of the day even if you have breaks. It also can make a difference if you measure with natural lights in the morning and artificial lights in the evening. Make notes on what influences your vision most. Tiredness? Lights? Stress? Long screen sessions without proper breaks? Other?

When you are outside and not wearing the reading glasses, just make sure you look at far away texts (shop signs, road signs, street names, number plates, etc) and far away objects (edges, details) as much as possible. When you get to below -2D you could consider not wearing contact lenses or any corrections when at home and / or switching to glasses.


thankyou so much for replying. well , i can read 20/13 in good lightning with my glasses left= -2.75 and right= -3.00. but wearing contacts(of recent prescption) left= -3.25 and right= - 3.00 makes me feel heavy. and i can’t figure out any good optometrist , i went to some they all just said , that wearing normalized while doing close up will not give you any strain , it’s a myth. so i wanna know , if i do my centimters average ( i have data) , and then subtract 1.50 . will this differential prescription be corrct??

To clear up a bit of misconception here: Le Rough Guide doesn’t really come with support outside what the community may offer here. Jake may chose to respond from time to time but direct support from him is part of the full paid program, so in the future skip the emailing him and addressing forum posts to him. This is a community and we all like to help each other as much as we can, that said we all have to put in our own work too.

It might be… try a plus 1.5 over your contacts and see how it feels. Typically it is a good idea to measure your desired distance for close up and use that to make a good choice. Try this page for further information: Differentials - EndMyopia Wiki

The goal of the EndMyopia method is to offer information that will help you make your own informed decisions, while a supportive opto is a great thing to have, in many cases people have to strike out on their own here.
Best wishes in your journey


By the sound of it you are seriously overcorrected. Your vision is still better than 20/20 with the weaker glasses? With contacts most probably you get super clarity (20/10? or 20/8? or 20/6?) which indeed feels like it’s pushing you away from things just “too much”. Anyway the contacts should not be stronger than glasses, especially not stronger than glasses that give you 20/13 vision.

I think under the circumstances you’ll be better off by measuring cms to blur (morning / evening; natural / artifcial lights, on a day with lots of screen time vs. little screen time), convert the average to diopters with this calculator and then deduct about 1.5D from those.
This may be a lot further away from your current serious overprescription than just +1.5D

Or as @Lloydmom suggest you can try reading glasses over your contacts. If you can find a shop that sells reading glasses, try +1.5D and then try +2.0D and see if you can still see things clearly at about arm’s length.


Yes, yes, and yes.

Please become proficient at measuring and you will be that much more in command of your situation.

Quadruple yes, all the more reason to get good at measuring.

You can do this, set fear aside… you can’t break something that was already broken for you.

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thankyou so much to all for helping me

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