Cataract Surgery - Replacing the Lens

Optical Lens Replacement surgery can be used to treat cataracts, which affect millions of people worldwide. We find out how the surgery works...
07 December 2008

Interview with 

Professor Sunil Shah, Midland Eye Institute


Helen - Now Professor Sunil Shah joins us now from the Midland Eye Institute. Hi Sunil. Thanks for joining us today.  I thought we could start off with the very basics, just how do eyes actually work?

The Human EyeSunil - It's a way of focusing light onto the retina. If you think of the eye as a camera you have the cornea which is the clear window of the eye and the lens which both focus the light onto the retina which is a bit like the film in a camera.

Helen - So we have this - the back of our eyes is where we're picking up the light. Now all sorts of things can go wrong with our eyesight and shortsightedness is when the image is focused in front of the retina long sightedness is when exactly behind the retina. How does that sort of thing change as we get older?

Sunil - That's a condition called presbyopia. What normally happens is that the lens in your eye actually changes in shape when you try and read. As you get older and typically that's about 45 or so the lens stops being able to react so well. Then you need to give it some assistance in terms of reading glasses.

Helen - So it is really just the close-up reading that becomes a problem. For example, I'm shortsighted and I think Ben is as well. Does that mean that as I get older I'm going to become less shortsighted or I'm just going to become both short and long sighted at the same time?

Sunil - No, that's a bit of a misconception. No there are two completely different mechanisms. To a distance you will remain shortsighted and you won't be able to see. But in addition you will have a reading problem. As it happens all that reading glasses do is make you artificially shortsighted.  So if you were shortsighted to the right amount you might get a away with not wearing  reading glasses but you still have a distance problem.

Helen - So I'll have to keep an eye on it anyway. Moving now to cataracts: what are they and how do they develop?

Sunil - Cataracts, we don't really know what causes them but everybody will get a cataract if they live long enough. There are many ideas on what causes them. One of them is related to sunlight exposure. Essentially a cataract is where the lens in the eye - so the lens is the size and shape of a smartie inside the eye - the lens actually becomes yellow and harder and this has an effect on the light getting through to the back of the eye.

Helen - So it sort of seems like your vision becomes cloudy and more indistinct as you get older, is that right?

Human eye cross-sectional view grayscaleSunil - If you're developing cataract, yes.

Helen - I take it that this is something that happens through time. Way back when we were all hunter-gatherers and so on we wouldn't live long enough really for cataracts to happen. If they did you'd be less likely to survive perhaps but not many of us are thankfully living much longer and so cataracts are presumably becoming a problem.

Sunil - Absolutely and also in the third world because there they do tend to develop a little bit earlier and there's still a lot of places where there is an adequate provision of treatment for it.

Helen - We can treat cataracts.  What can we do to help people who have developed cataracts?

Sunil - This needs an operation and the lenses inside the eye are the cataracts and so it does need a full operation. Lots of people we see think we can do the surgery with a laser but that's not really the case. What we do is create a small hole and the hole's are between two and 3mm large and. We remove the contract from inside the eye. In the space where the contract would have gone we put a plastic lens in its place.

Helen - So you take the whole lens out?

Sunil - Well, we - it's a little bit more complicated than that. If we go back to the smartie analogy what we actually do is you break open the candy coating on the outside and remove all chocolate. In the candy coating we put in the plastic lens.

Helen so you squirt that back in.

Cataract in Human EyeSunil - Well, it's a solid lens. We can either roll it or fold it. It goes in through the same 3mm hole.

Helen - Once you've done that that's all that you need to do. That's a one-off operation and they have much better vision for the rest of their lives.

Sunil - That's correct.

Helen - Replacing lenses to cure cataracts, that's one thing.  Is there anything else we can use the surgery for?

Sunil - Well, we use lens surgery instead of laser surgery and in people who want to get rid of their short-sightedness as well or their long-sightedness. It's not a procedure you'd choose for somebody who's younger. you can organise a small prescription but certainly there are indications for it. For example, some while ago I treated someone whose prescription was -27.

Helen - Goodness me. That's enormous!

Sunil - Yeah. Most people think they're pretty bad when they're minus two because they can't see the top letter on the charts. But if you think this person was ten time as bad.

Helen - That's incredible.

Ben - Replacing the lens for the same reason that you have laser eye surgery. Later on in the show we have a package about laser eye surgery. One of the things they told me is that if your eyes are going to change over the next 5 or 10 years anyway then laser eye surgery won't stop that from happening. Would lens replacement surgery mean the further degradation of it won't happen?

Sunil - In general most people's prescription doesn't change after their early 20s. So if you've got evidence of no change over a number of years it's actually extremely unlikely they'll change after that time. Certainly that's why the College of Ophthalmologists recommend that though we do not do laser eye surgery until someone's 21. You have to take each person on what the prescription is, what the state of their eye is, what their requirements in terms of job and hobbies are before you decide to operate on them.


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