A very common question that we get is why do I need reading glasses? What's actually happening to the focus? What's happening to my vision to be changing so I can’t see things up close?
We all have seen it when you can’t read things up close, when you have to start pushing things away from you to read, and then further and further away as we age. And there's that joke that your arms aren't long enough anymore. Well, what's actually happening is a condition called Presbyopia, the natural loss of focus with age. It's a natural aging process of the eyes. So it's going to affect every human on the planet in some shape or form. It usually hits us by mid 40s, we get some people in on their 40th birthday, you get some people make it closer to 50, but it's in the 40s when it's going to take its effect.
Now, unfortunately as time goes by it is going to get worse because it is down to the aging process of the eyes. It doesn't matter whether you're wearing glasses, not wearing glasses, it's going to get worse. An optician can actually look at your date of birth and we'll already know basically what power reading glass addition on top of your normal lenses you're going to need to see, because it is literally that strongly linked to age.
A lot of people think that you go long sighted with age, and you can understand why people think that because long sighted people struggle to see things up close. And as people start to struggle to see things up close, people assume it's long sightedness, but long sightedness is different, it's down to the anatomy of your eyeball, the curve of the front of your own being maybe too flat, the eye being maybe too short and not getting the focus quite right. Whereas, this is literally down to changes in the lens of your eye. Which means it can't focus as well. You also get the flip of that, which is short-sighted people who naturally will see things up close when they don't focus. So they can take their glasses off and see things up close. You see people do that, they'll lift their glasses up to read. But with glasses on, they’ll also get to the point in their mid 40s where they can't see to read and have to take them off to use their natural short sightedness.
So it’s all to do with changes in the lens in the eye. People think it's the muscles that pull the lens - are the muscles wearing out?, Are they becoming less effective? Well, they're the same muscles that do your far distance focus, so they're not really getting worse. The muscles are fine because if you think about it, say if you didn't need glasses and you looked at something 6 feet away and then suddenly switched your focus to 10 feet away, your focus will change just like that. So those muscles are fine, it's the changes within the lens itself in your eye that makes it harder to change the shape of the lens.
So behind your pupil and iris sitting in the front of your eye, just in the front of the main body of your eye, you've got the lens, and the lens is shaped a bit like an oval if you took a cross section through it. And as it changes to focus the light, as you look at different things it's changing its focus making the lens fatter or thinner or more curved or flat. Now to do that, it's got a ring of muscles around it to pull the lens, push the lens, to kind of change that shape. When we're young, it's a lovely tight system. The lens is attached to these muscles by little ligaments and it's all beautifully taunt and tight. So as soon as that muscle changes and contracts, say, it's going to move the lens very quickly into those positions. So children and young adults have a massive amount of focus available to them.
Now, it used to be thought that lens was just going hard and in some cases they have found when they're doing cataract operations that some people's lenses do harden with age, but not everyone's. So the lens is maybe going harder, but also the lens is kind of growing a little bit. A simple way of thinking about it is to think of it a bit like an onion and an onion as it grows, gets more layers to it. So, that's kind of happening with the lens. So it's a very tiny imperceptible growth in the lens, but it makes a huge difference to the system. If the lens is growing a little bit, it's getting closer to the muscle, so the ligament is going slacken. So then when the muscle moves and tries to contract, to move the lens, it has to get the ligament tightened first - it has to act on the ligament and tighten up before it can act on the lens. So as the lens is getting bigger and closer to the muscle, it gets harder and harder and harder to do that. As time goes by, this gets worse.
That's why presbyopia and that loss of focus for close worsens with age. As time goes by, you need stronger and stronger reading glasses. It's nothing to do with wearing the glasses. It's nothing to do with not wearing the glasses, as I've said, it really can't make a difference. It's literally down to a function of your age. And as time goes by, you get your first reading glasses and you find you've got quite good depth of focus with that, that's because you still have a good bit of focus left. So you only need a little bit of help from the glasses and a weak lens. What people don't realize is the reading glasses only have one focal point. It's just one lens that does one focal point. So let's say it’s focused to about a meter in front of you, now it's your eyes that then focus the distances around that and give you that depth of focus. So as time goes by and you're needing slightly stronger lenses to see the small stuff because you're losing more ability to focus, your depth of focus also decreases too because you don't have enough focus to push the boundaries of where that clear area is.
Hopefully that helps to explain a little bit and answer that question of why we need reading glasses. It's a very common question, as it's something that happens to every single human in the world in one shape or form. It's presents differently for people who are longsighted and short-sighted, but those lens changes are what's going on for everyone. That's why we need reading glasses, that's why we need extra power to see up close.