I heard you need less astigmatism for closeup, but won’t you get astigmatic blur since that axis has light not fully in focus. I want to order differentials I have -1.25 cyl, I’m thinking I could get away with -0.5 or -0.25 cyl decreased and active focus to slowly reduce my cyl dependance but I’m not sure if this will affect my stimulus for my normalized which I haven’t touched cyl for. It’s only -0.25 reduction sphercially. I just heard you need less astig for closeup, my previous differentials accidently had no cyl and I could manage at night but not a lot has to active focus a ton. Why do we need less cylinder for closeup? I have -3.75 and -1.25 astig. This means at around 27 cm I see clarity and directional blur. Only if I go beyond that point will my astig decrease since my less round part of my rugby lens will bend more decreasing the rugbyness and making it more spherical so if Im 60 cm away I still have -1.25 astig. If I was 20/20 and had -0.5 cyl then yes I would probably definitely need no correction for closeup since the eye shape evens out. I’M CONFUSED AS TO WHY WE NEED LESS CYL for closeup. I under stand the spherical but why would the difference decrease between the axis adn the rest of the eyball if it wont bend more to cancel out the difference. I need guidance
The usual recommendation is to have the same cyl in both pairs of glasses at the start and with the first few drops only drop from sph. Exception is if you are (or if you suspect that you are) absolutely overcorrected on cyl, too. In that case you can have an initial drop from cyl between 0.25D and 1D.
How much? It will depend on your eyes and on how much you got used to the cyl. If you just had an opto measurement and that suggest a higher cyl by 0.5D for the next opto glasses, then just don’t take the higher one and keep the old value for cyl (unless you were blind as a bat with the previous pair of glasses you wore up until now.) Otherwise, the most typical is to try dropping 0.5D cyl.
When you start reducing cyl and if you prefer keeping the reduction of norms and diffs apart then start reducing in diffs. If that works well, you can consider dropping cyl from norms, too. Other people prefer dropping the same from both at the same time, so they change both pairs of glasses.
So it is not ok to have more cyl in diffs than in norms. It’s OK to have the same cyl in both. It is ok to have less cyl in diffs. Why? Because most people find AF first with close up vision and can use it to clear not only the sph blur but also the astigmatism part, too. But they may get too much directional blur at distance.
You really helped BiancaK, thanks. However, I was thinking last night perhaps the thing is that when we are far blur makes more of difference rather than reducing 0.25 from diffs where things still remain pretty similar and unnoticable really. I am going to reduce 0.25 cyl from my new diffs because I know I will be using those diffs for 2 sph reductions at least, I will just put the computer or chair farther as those reductions occur. Later, my next normalised after 2 sph reductions would be 0.25 cyl less only and then my diffs will also have same. 0.25 doesn’t affect you too much and I will sit at edge of sph blur that way I would only get a little astigmatism blur if I even do notice, I would easily clear it up training me for my cyl reduction after my 2 sph reductions. You think that’s a good idea? I think it is
Glad to hear I could help.
You are right, in close up the brain is better at ignoring those “smudges” around the edges. They are there, just not noticed. At distance the smudges are proportionally bigger compared to the smaller objects you are looking at, so it’s difficult for the brain to ignore them.
Sounds like a plan
With EM you prepare yourself with formulas but then you just have to kick off the process and measure the results. Bit like cooking: reading the recipe, learning a lot about ingredients, how to balance flavour, you can even go deep into food science, but the thing is: you’ll use the ingredients you have, you’ll follow the process and then you’ll taste the result and modify the seasoning if need be.
You seem to be ready for the dive, go for it.
And don’t forget to post an update every couple of weeks. We like to cheer each other on the journey and it’s encouraging for others.
sure, I shall.