How to know what strength readers to use?

I have pain with reading and this has been since I was 39. It started when I went for a glaucoma test two years ago. I don't know if my eyes got hurt or if it's just typical aging. How can I tell? My prescription is +5.5 right eye, +8.0 left eye (which is a lazy eye). I have tried different readers over my contact lenses but it still hurts. I've tried +1.25 and +1.75. Should I try something even stronger? How can I know which strength to try (it never becomes blurry- I can always adjust my focus to see whether I use no glasses or strong ones. I think because my eyes have been bad all my life I just got used to focusing really hard)? Thanks for your help!

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