The first symptoms are usually noticed between the ages of 40-50, though in fact the ability to focus declines throughout life, from an accommodation of about 20 dioptres (ability to focus at 50 mm away) in a young person to 10 dioptres at 25 and levelling off at 0.5 to 1 dioptre at age 60 (ability to focus down to 1 -2 metres only).
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