How to measure
Sit in front of the computer (or a book), without glasses. Do this before you start using glasses, in the morning. Start up close and slowly move back until the text starts to look blurry. You want to catch the ‘edge’, where things are still sharp, but just so. Another small move backwards, and things are starting to blur. Make sense? You want the distance where you can still see clearly!
The role of the eye chart
If you can see better than 20/20 (6/6) on the chart with your glasses, they’re too strong for improving eyesight potential. That’s because you need the blur horizon to practice active focus.
Conversely if for example you see only 20/50 and barely that, your glasses are probably not offering enough help.
If your myopia is under about 2 diopters you problably can read without glasses and you don’t need differentials, you can just start using acitive focus without glasses ( see next chapter )
Your differentials should give you at most a little bit of blur in your most common close up activity.
For a lot of people this is working behind the computer. It is very important that they enable you to easily perform your close up activity, while maintaining an ergonomically correct and relaxed position, with having at least 50 cm distance ( more will give less eyestrain ) from your close up activity.
Ideally you should be just at the edge of blur:
https://endmyopia.org/focal-calculator/images/blur.png 2
The strength of the differentials will be roughly 1.5 diopter below your current full prescription. Maybe a bit lower if you are overprescribed and maybe a bit higher if you current prescription is already giving you some distance blur.
abbreviation
OD: Oculus dexter, this is Latin for right eye
OS: Oculus sinister, this is Latin for left eye.
SPH: Sphere, this indicates the lens power in diopters.
球镜 ------ 近视或远视度度数
CYL: Cilinder, this indicates the amount of astigmatism, or directional blur.
柱镜 ------ 散光的度数
Axis: The axis of the cilinder correction.
轴位 ------ 散光的方向
PD: pupil distance. The distance from the center of both pupils in mm. It also can be written in 2 digits.
Active Focus
Beginner Tips: https://www.youtube.com/watch?v=YtL9rL-u_7g
https://www.youtube.com/watch?v=QzzkC6qIpV0
https://www.youtube.com/watch?v=jRbzBfFPjVI
https://www.youtube.com/watch?v=_-ZblT8Zg84
Another thing that is very important is the amount of good (and preferably natural) lighting that is available. If this is insufficient, it can affect Active Focus profoundly.
Some normal side effects to Active Focus are a little headache and pain or pressure in your eyes. This is completely normal and it happens because your eyes and your brain start working actively on seeing clearly again.
it should be gone in no more than a week. Keep in mind that (done properly) it shouldn’t amount to more than a little discomfort.
It’s also very possible that you may experience watery eyes while practicing Active Focus, especially outside. This is nothing to worry about, it happens to some and is usually gone within a minute. This could also be a sign of having dry eyes.
The progress
Do keep in mind that the standard rate of improvement is about 0.75-1.0 diopters in the first 3-4 months. After that it slows down to 0.25 diopters every 3-4 months. Also the amount of lighting can greatly affect how everything is moving along.
In winter times with less ambient lighting being available you may very well slow down or even stop improving altogether. Do know that this is completely normal and progress should pick up again when there’s more natural sunlight available for your eyes.
Differential prescription vs normalized prescription
https://endmyopia.org/differential-prescription-vs-normalized-prescription-considerations/
The differential prescription: You want a blur horizon, but you want it where you can comfortable reach it, while maintaining good posture.
Where is that distance for you? This can be a personal preference. Anywhere from 20/30 to 20/50 on an eye chart may be suitable.
Driving and other activities requiring 20/20 aside
For the first normalized prescription I often suggest to get to 20/30
Now you already know how you feel with 20/30, and once you improve that to 20/20 or better, you might want to simply repeat the experience with a similar reduction.
The differential prescription tends to be around between -1 and -2 diopters lower than your previous full prescription.
The myopia calculator is a good starting point to make this assessment.
For those of you already familiar with these concepts, the take-away is that you always want to prioritize ergonomics for differential, and personal preference for normalized.
Don’t reduce differentials and normalized at the same time. Wait 4 to 6 weeks before you are reducing one (your differentials for instance), than after 4 to 6 weeks later you can reduce the other (normalized in this example).
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