Difference between revisions of Guide:Reducing differentials
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This guide will show you how to reduce your differential prescription. Can't have any of that nasty [[close-up]] without the reduced lenses. | |||
==Complicated way with math== | If you don't use differentials at all, or are overcorrected for a given distance, your progress will be stunted. Accommodation of the eye to [[hyperopic defocus]] is the main reason [[axial elongation]] happens in the first place. | ||
==Reducing== | |||
Stagger reductions between differentials and normalized, unless equalizing. | |||
Following the principles of [[zero diopter reset]], if you already wore the previous differentials, do not wear the new differentials until the next day. | |||
==First differentials== | |||
===Simple way=== | |||
The EndMyopia process will probably involve a lot of trial and error. Bearing this in mind, Jake recommends you reduce from your glasses prescription by about '''1.25 diopters'''.<ref name=ChooseReduction>{{cite jake|https://endmyopia.org/choose-reduced-glasses-prescription-differential-close-friendly-glasses/|How To Choose A Reduced Glasses Prescription (Differential / Close-Up Friendly Glasses)}}</ref> This will depend on the distance you work from the screen, so reduce it by less if you work farther from the screen. Between 1-2 diopters is a good range - anything more than that and you'll probably want to double check it's a good idea. | |||
===Simple way with math=== | |||
1. Measure the distance to your monitor (in centimeters). | |||
2. Convert that number to diopters. | |||
3. Subtract the number you just got from your full prescription. | |||
===Complicated way with math=== | |||
The base point is an [[emmetropic eye]] with 20/20 vision. | The base point is an [[emmetropic eye]] with 20/20 vision. | ||
Everyone has a different level of myopia, and depending on this you can calculate the required amount of correction to just see the object, based on how far away it is. | Everyone has a different level of myopia, and depending on this you can calculate the required amount of correction to just see the object, based on how far away it is. | ||
Firstly, find out the distance from you to the object. In plain English, how far away is the object in centimetres? | Firstly, find out the distance from you to the object. In plain English, how far away is the object in centimetres when (without glasses) you can still just see it in focus? | ||
Type in the cm value you get into [https://endmyopia.org/focal-calculator/calc.html EndMyopia diopter calculator] to figure out the '''difference''' between your full strength prescription glasses, and what you actually need to see the screen. | Type in the cm value you get into [https://endmyopia.org/focal-calculator/calc.html EndMyopia diopter calculator] to figure out the '''difference''' between your full strength prescription glasses, and what you actually need to see the screen. | ||
Then, take the difference and subtract it from your full strength prescription glasses. ''Voila!'' you have a differential prescription. | Then, take the difference and subtract it from your full strength prescription glasses. ''Voila!'' you have a differential prescription. | ||
<div>'''More explanation at [https://wiki.endmyopia.org/wiki/Optics_related_math#Calculating_correction Optics-Related Math > Calculating Correction].'''</div> | |||
===Example=== | ===Example=== | ||
Suppose you have [[Guide:OD/OS|OD/OS]] -4.25/-3.25, and you see, or want to see your monitor | Suppose you have [[Guide:OD/OS|OD/OS]] -4.25/-3.25, and you see, or want to see your monitor 57cm away from where you sit. | ||
Go to the [https://endmyopia.org/focal-calculator/calc.html calculator], and enter in 57cm. The result is '''-1.75'''. Subtract this value from both of your eyes (be careful with negative numbers). | |||
<math>OD\ (right\ eye): -4.25-(-1.75)=-2.5</math> | |||
<math>OS\ (left\ eye): -3.25-(-1.75)=-1.5</math> | |||
So, you should use OD/OS -2.5/-1.5, if 57cm is the main distance you perform [[close-up activity]]. Simple! | |||
=== Plus === | |||
If you have [[low myopia]] and get a positive number, don't wear any glasses for close-up work, and read the caveats about [[plus lenses]]. | |||
==References== | |||
{{reflist}} | |||
== See also == | |||
* [[Guide:How to measure your eyesight | How to measure your eyesight]] | |||
* [[reduction | Reduction]] | |||
* [[Differentials]] | |||
* [[Guide:Reducing lens complexity | Reducing lens complexity]] | |||
* [[Guide:Reducing normalized | Reducing normalized]] | |||
* [[Guide:Not_reducing_too_quickly | Take it slow]] | |||
[[Category:Guides]] | |||
Latest revision as of 22:23, 11 February 2022
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This guide will show you how to reduce your differential prescription. Can't have any of that nasty close-up without the reduced lenses.
If you don't use differentials at all, or are overcorrected for a given distance, your progress will be stunted. Accommodation of the eye to hyperopic defocus is the main reason axial elongation happens in the first place.
Reducing
Stagger reductions between differentials and normalized, unless equalizing.
Following the principles of zero diopter reset, if you already wore the previous differentials, do not wear the new differentials until the next day.
First differentials
Simple way
The EndMyopia process will probably involve a lot of trial and error. Bearing this in mind, Jake recommends you reduce from your glasses prescription by about 1.25 diopters.[1] This will depend on the distance you work from the screen, so reduce it by less if you work farther from the screen. Between 1-2 diopters is a good range - anything more than that and you'll probably want to double check it's a good idea.
Simple way with math
1. Measure the distance to your monitor (in centimeters).
2. Convert that number to diopters.
3. Subtract the number you just got from your full prescription.
Complicated way with math
The base point is an emmetropic eye with 20/20 vision.
Everyone has a different level of myopia, and depending on this you can calculate the required amount of correction to just see the object, based on how far away it is.
Firstly, find out the distance from you to the object. In plain English, how far away is the object in centimetres when (without glasses) you can still just see it in focus?
Type in the cm value you get into EndMyopia diopter calculator to figure out the difference between your full strength prescription glasses, and what you actually need to see the screen.
Then, take the difference and subtract it from your full strength prescription glasses. Voila! you have a differential prescription.
Example
Suppose you have OD/OS -4.25/-3.25, and you see, or want to see your monitor 57cm away from where you sit.
Go to the calculator, and enter in 57cm. The result is -1.75. Subtract this value from both of your eyes (be careful with negative numbers).
So, you should use OD/OS -2.5/-1.5, if 57cm is the main distance you perform close-up activity. Simple!
Plus
If you have low myopia and get a positive number, don't wear any glasses for close-up work, and read the caveats about plus lenses.