Why does eyesight tend to get worse with age? and why does this worsening eventually plateau?
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Not an expert on this, yet two possible reasons come to my mind: The flexibility of the lens decreases over time, so certain distances can get out of focus. Some might get a cataract at higher age – which is basically the lens getting cloudy – due to e.g. exposure to UV light.
When you grow up, your head and eyes shape grow and change too. If it doesn’t grow right, you’ll have problems to see objects from a far distance. When your head stops growing (age 20-25) it plateaus.
At age 40-45 something else happens. The muscles that control your eyes are stiff so they can’t contract enough to put something in a close distance on focus.
Soft tissue losses elasticity. When you’re young the protein cells look like straight spaghetti moving back and forth and as you age the cells look more like basket weaving. I am currently at the picnic basket stage of my life.
I had the benefit of always having shitty eyesight, and got cataracts when I was 38. Two eye surgeries and two artificial lens implants later, I can honestly say this is something I know a bit about.
So, first and most important, behind your pupil you have your lens, which is basically a clear, jelly filled sack connected to muscles that stretch or compress the lens, which changes its shape, which allows you to focus.
As you get older, the lens becomes less flexible, it slowly hardens which reduces your ability to focus. This is why a lot of older people need reading glasses. Their lenses are no longer flexible enough to be able to change shape enough to focus on things close up.
Because I had my natural lenses replaced, my artificial ones don’t change shape at all. My eyes are basically fixed focus…so while my distance vision is fine, I can’t focus on anything close up, so need reading glasses for that. This is basically the same as your lens hardening (but without cataracts).
Plus, there are other things that affect your vision as you get older. Your eyes are precision bits of equipment, and things like the pressure inside your eyeball, scratches or damage to your cornea, your optic nerve degrading with age all play a factor.
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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