Eliminating astigmatism in normalised first

Old prescription right -3.75, -1120 left -3.50,-.7540
New prescription from ophthalmologist
Right -3.75,-1120 left -3.75,-.7540
I wanted to ask is it ok to eliminate cylinder as my cylinder is less than -1 d
Can i exchange -1d of cyl with -.50d of sph
I am planning to get -4.25d glasses for both eyes
Am i going right ?
And how much time visual cortex take to adapt to cylinder changes ?

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Hello, and welcome to the EM journey :smile:

Unfortunately we can’t give diopter specific advice. You’ll have to experiment, make a fully informed decision and be ready to take a step back if it doesn’t work. In this sense, the answer for all “can I” questions are, yes you can. You drive your own boat, your decisions are the only ones that count.

Whether that is a good idea, though, is another matter altogether. EM does not recommend reducing cylinder in norms before diffs. In addition, some people can substitute some cylinder with spherical, others cannot. There is no one-size-fits-all answer; we have guidelines, and sometimes we ignore them, not because it’s the right choice but because we’re a bit stubborn and/or lazy and like to find things out the hard way.
And honestly, your sph/cyl ratio isn’t that bad, so I don’t see point in rushing to get rid of the cylinder correction.

So, yeah. No diopter specific advice. It’d be wiser to remove the cylinder in differentials first before messing with distance vision. And removing cylinder cold turkey isn’t particularly recommended (I suggest reading the article on the blog on how to reduce prescription complexity), but it doesn’t mean you can’t do it.


If you don’t have differentials yet, start with choosing the right differentials for yourself and you can think about normalised glasses 4-6 weeks later.
Do you have a few weeks of measurement to blur yet? each eye, both eyes, morning, evening, rested, tired, daylight, artificial lights? What have you learnt about your eyes so far?

My differentials are -2.75 both eyes
My left eye is seeing great but right has some astigmatism

Your substitution for cylinder reductions with spherical is correct. Last month I just removed my 0.75 cylinders in my normalized to 0.0 and added back 0.5 spherical and my eyes are adjusting nicely, slight blur that I can easily clear up.

But it can take your visual cortex some 6 months to adapt to cylinder changes. When I first did a reduction for my cylinder which was -1.25 to -1.0 it took me about 4 months before my eyes adjusted but I didn’t add back spherical for it.



I removed it 6 monhts ago (-2.25 and -1.25 in contacts / -3.00 and -1.75 in glasses for diffs), and not used more than -1.50 in norms, yet everything was the same. And I usually was adding back spherical.

So different astigmatism cause, different results. Lens-induced astigmatism usually should subside readily.