Why does eyesight tend to get worse with age? and why does this worsening eventually plateau?
In: 8
It’s called presbyopia, and it happens to everyone.
The lens in your eye is flexible, and you tug on it and bend it whenever you want to focus on something up close. As you age, starting at around 40, the lens starts to lose its flexibility. But the muscles pulling it don’t get any stronger, so it doesn’t bend as much. Since you need to bend it to focus on close things, you lose the ability to focus on those close things, and how close you can focus on things gets worse and worse so farther and farther over time. That’s why you see older people shoving something they’re trying to read out as far as their arms will go, so that even though it looks smaller, at least it’s in focus.
Reading glasses fix this by helping your eye out so you can focus on close things again. But it trades off having far things in focus for it, hence the swapping on and off of reading glasses depending on what you’re looking at. Bifocals have two curvatures on them, so the downward-looking part of the bifocal works for close up, and the straight-through part works for far away. This is where you get people tilting their nose up while inspecting something close by.
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