Myopia is when things far away blur, corrected with a concave lens; hypermetropia is when nearby things blur, fixed with a convex lens. Power in dioptres is the inverse of focal length. But in my life, it's not so simple—I have hypermetropia, but now presbyopia has also come, beta. My reading glasses are convex, but no formula from a book prepared me for the surprise of needing two pairs, one for my sewing and another just to see your face clearly on the video call.
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