My first differential

I started my journey last month with left -6.75 cylinder -1.00 and left -3.75 cylinder -1.50, I already got my normalized at -6.00 and -3.00 currently to have a bit of chanllenge for active focus, and in the morning I actually see crystal clear with this pair of normalized.

For the differential, going with Jake’s general method, it would be right: -5.75 with 0 cylinder and left: - 2.75 with -0.5 cylinder?

Just want to get more opinion on this since I am still doing active researches but want to stop looking close up with my regular glasses.

Thank you all!

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I am confused here… You got your normz first? Did you retain the cylinder? Diffs are the first step usually but in either case this should help: Differentials - EndMyopia Wiki


OMG. You must have been seriously overprescribed by the opto, if you could simply drop 0.75D and you don’t even notice it… How does the clarity change by the end of the day?

The rule of thumb for diffs is +1.5D SPH from the original opto prescription.
When you suspect that the cyl may also be overprescribed, you can drop from that, too, to avoid too much unnecessary correction close up. However, this may reduce the drop suggested in the rule of thumb.
Note: Differentials should have the same or less cyl then normalised do.
So joining in with @Lloydmom, did you drop all the cylinders from the normalised, or you didn’t mention cyl as you just kept the same?
Note2: If you feel totally OK with your current normalised then imo you could do with more drop than your planned differentials. Typically there is at least 0.5D difference between norms and diffs, actually usually more than 0.5D difference, but it also depends a lot on the distance to screen in your typical work or study set up. It does matter if you are just trying to get the minimum distance of about 50cm or prefer to benefit from peripheral vision, too, at about 75cm or more.

Have you measured centimeters to blur yet instead of simply working with the rule of thumb?

Thank you Bianca for the detailed reply. Yes my normalized has the prescribed cyl so I did not mention it. I notice that if I use my eyes for close up a bit more on a day then things get more blurry towards the end of the day with my normalized. I just found my old optometrist measurement my right was -7 with -.25 cyl and my left was -4.25 with -0.75 cly back in 2016 when I was in university using my eyes for close up more than now. So my diopter actually dropped without me doing anything for it.

I have been wearing the same glasses at -6.25 on right and -3.25 on left tho for more than 4 years.

I have just now measured the centimeters to blur using the link, and right now my left is -3.75(26) and my right is -5.5(18cm). I used the app before but it seems to not able to show any distance below 17.6cm, and the diopter shows different than this website as well. My measurement through the app is left -3.75(27cm) and right-4.75(18cm).

I don’t think the optometrist in my location(Canada) is allowed or encouraged to prescribe lower diopter…

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Thank you for the reply. Yes I retained the cylinder for my normalized. I looked at the wiki link you attached, it has the suggestion for people who has -0.5 to -0.75 cyl. should I decrease the cyl by -0.5 and add+0.25 to the diopter for each eye? So I have consistent focal plane?

There are a number of ways to do it, and different people have different experiences. You do have to make a best guess and go for it. Like I said before with Diffs you have a safety net in that you can move closer if there is too much blur or you can push back a bit if there is no blur still and then you will have that data point too to work off of moving forward. Feel free to keep poking around on the wiki too so much information there. Best wishes

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Optos rarely prescribe differentials or even normalised that’s why we order glasses online from the likes of Zenni.

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