Basic Principle of EM: AF at 80cm vs. AF at 3 Meters

Dear all,

I still try to understand the basic principles of EM.

I understand that to some degree my myopia is caused by ciliary muscle spasm (pseudo myopia) and to some extent lens-induced myopia (prolonged eye ball). I understand that we do AF to teach the ciliary muscle to relax again on its own and this stimulus (or the myopic defocus) tells the brain to shorten the eye ball again.

Now, let’s imagine the following scenario:

My laptop is 80cm away and my TV is 3 meters away.

I use my Differentials on the laptop and my Normalized for TV.

In both cases I see at the EoB, i.e. I have the same blur challenge in both scenarios!

Without glasses my EoB starts at 40cm, so that is the maximum my ciliary muscle can relax on its own.

Why is it “better” to watch TV with my Normalized than to sit at a PC with my Differentials? I mean, in both cases I see at the EoB. That means that my ciliary muscle is already maximally relaxed in both cases, it cannot relax more because of the ciliary muscle spasm! If I do AF, my ciliary muscle needs to relax just as much in both cases (same stimulus?) because it is the SAME BLUR CHALLENGE or not?

Of course it is another story if someone doesn’t need glasses at all. Then 3 meters is definitely better than 80cm because the ciliary muscle does all the work here, it is more relaxed at 3 Meter than at 80cm. But in my case, my ciliary muscle can only relax until 40cm on its own, from then on glasses do all the work.

I really struggle to understand this, it just does not make sense for me. Hope someone has an answer for me :smile:


I was wondering the same thing! I look forward to hearing some thoughts on this too

When you are looking at a near object, 3 things happen: your eyes turn inward to form a single image, your pupil is smaller and your ciliary muscle adds more diopters to the lens. The farther you are, the less those effects kick in


There is definitely confusion that occurs when trying to understand the EM way.

The short answer to your question is that blur challenge and AF at closer distances is just as beneficial as longer distances (using different glasses of course). I get relatively little distance challenge (especially in Covid days when I don’t drive much anymore). Most of my AF/blur challenge is either with my PC doing work for hours every day, naked eye with my phone, or watching TV. And yet I’m still progressing at 0.75 to 1D improvement a year.

The suggestion of distance based recommendation and such has two reasons, IMO. The first is that looking at far away stuff is “good” (much like eating “healthy” food is good). I feel this is accentuated by many who feel “screens” are a bad thing (and they can be with the wrong glasses, as we all know). The second is that long term projects like reducing myopia require habit, and simplicity. Juggling multiple prescriptions for each situation (e.g. glasses for phone, different pair for PC, different pair for TV, different pair for driving, etc) is a hassle, and thus can lead to someone “cheating” (I don’t want to swap glasses so I’ll look at my phone with distance glasses just this once), or worse, people giving up altogether.

I juggle many different focal distances (phone/book, laptop, PC, TV/normalized, driving). That’s 4 different pairs plus naked eye, each with their own step-down schedule. It’s ok for me because I’m OCD about EM =) But most people aren’t OCD like that, so just talking about differentials and normalized (along with breaks to look far during closeup time) is “enough” to ensure progress. But it might not be “optimal”, if (like me) you want to maximize blur challenge/AF-time.

So like most things in EM, do what works for you and achieves my goals. Mine involves many glasses. Others just want to live their lives and just have two pairs. So do what makes sense for you! :slight_smile:


A beautiful concise summary of an area we have investigated before. I often wonder what happens in the visual cortex when the accommodative triad is disrupted by myopia i.e. ciliary muscle contraction/relaxation is no longer linked to vergence as it is in the emmetrope. To clarify, if one’s blur point is at 20cm the ciliary muscles are fully relaxed when viewing at that distance but the eyes are still converged.

1 Like

@Hoofjr and I agreed to slightly disagree in this area a while ago :laughing:

Not necessarily because we are contradicting each other, but more because of us being at different stages in our journey (over -1D and under -1D), voting differently on the necessity of dynamic focal plane changes (smart phone - monitor - TV - driving is relatively easy to separate and allows changing glasses at static distances vs. climbing mountains looking in front of your boots, checking where the others are, where the destination is and admiring the view doesn’t allow changing glasses at distances changing dynamically), having different screen times (3 screens: smart phone - laptop/PC - TV vs. 1 laptop screen with no TV and minimal time on smart phone), and different goals.

So my take on your question:
At the beginning it is enough to enjoy close-up in differentials and everything else in full prescription. At a later stage you will introduce norms and first those are OK to be worn for TV. As time progresses and your eyesight improves, most likely you will prefer your differentials when indoors for all distances (and as Hooofjr says, if you have fixed but different distances for different screens, you may find it useful to introduce different differentials for them; if you mainly use the laptop as “the screen”, you’ll be OK with one pair of differentials good for that distance and wear those for all other indoor distances, too). When your eyes without corrections become your differentials and your norms are below -2D, you will need proper distances to keep improving, simply because mid-distance will not give you enough challenge anymore. This is assuing you want to have clear vision over 20m, too, and be able to switch between distances dynamically.

I’m still learning the ropes, but it seems to me that regardless of distance, the point is to have enough blur to create a stimulus for your eyes. This way your eyes know that they are close but need to work to improve themselves. This can be reinforced through active focus, print pushing, or intention while looking at slightly blurry objects.

If I follow what @BiancaK is saying, as your vision improves you’ll get this stimulus at further and further away. So people with higher myopia can start with naked eyes and differentials, but as you get closer to 20/20 you’ll need to use normalized glasses and distance vision to get the blur horizon that you need for improvement.

That all makes sense to me anyway.