Keeping the eyes progressing together

Help please with a question about equalizing and balancing.

Over the past year I’ve been wearing normalized and differential. I became aware that one eye had become much stronger than the other and the optometrist confirmed that in fact the weaker eye has developed worsened astigmatism of -1.25 which she thinks might be contributing to migraine.
So I am looking to make the weak eye more active, as it seems to be letting the strong eye take the lead and so is worsening.

Please could you link to any topics about how to deal with this.

I am aware of three principles to take into consideration:

  1. for normalized, presumably i follow the rule to ‘add 0.25 of sphere when deducting 0.5 of cyl’

  2. for close up i might not need cylinder. does that mean i don’t need to follow the rule to ‘add 0.25 of sphere when deducting 0.5 of cyl’?

  3. the rule to keep all prescriptions in the same proportions seems to contradict the above 1 and 2?

I would also like to ask what is the best value trial lens set currently available to the UK, that is good enough to be useful.

1 Like

Sorry to hear that, but glad you’re taking care of your issue now!

1 - yes, you do understand.
But note that when you have, let’s say, -3 with -1 cyl, you probably won’t replace -1 cyl by 0.5 sph, but instead do it in 2 steps: first you might need to change to -3.25sph and keep -0.5cyl.
You’ll have to find out how much your eye tolerates and it’s probably best to start with small changes.

  1. This depends a bit on your cylinder. If you have, let’s say -3.25 and -0.5 cyl as your normalized (starting from -3.00sph and -1 cyl), you can try if you can just drop cyl, yes. So maybe -2.00 sph 0cyl could work (remember: try for yourself, everyone is different!) This would not work at cyl higher than 1, usually.

  2. A clear yes-no to this! :joy: You still have the same diopter gap: from normalized to differentials, you would reduce both eyes by the same sph and by the same cyl value.

  3. I have no idea, but a helpful opto might help you find things out and let you play around?

Search terms for the blog and here:

  • reducing prescription complexity
  • diopter ratio
  • patching

Keep going, and keep us posted - you’ll get there! :+1:


Hi Tii, Thank you for your kind and thoughtful reply.

My right eye is straightforward, but full correction of my left is now -5.25sph -1.25 cyl. For the past year I’ve not had any cyl in it, and during that time, the cyl has increased from -0.5 to -1.25, with increased ocular pressure, and there has also been some impairment in binocular vision at a distance which was ok previously.

The optician suggested I try -0.75 cyl, but I thought it might be a bit of a strain going from zero cyl to -0.75, and I had in mind more -0.5cyl.
At the same time I realise I need to apply a decent amount of cyl because things have been going the wrong way for this eye, presumably because the other one is doing the work.

Without a trial lens set to hand I am struggling to decide whether to apply -0.5 or -0.75 cyl to the lagging eye, and would appreciate any advice as to how I can work out what would be best, without having a trial set.

Thank you.

Test lens kit.

I’d spend the extra and get one from Amazon so it can be returned if it doesn’t measure up.

See my post about test lens kits, but tl;dr version is good glass lenses, metal rims, and spring for an adjustable frame. They’ll hold more lenses and help you find your pd.