Science Interviews

Interview

Sun, 7th Dec 2008

Laser Eye Surgery

Reena Gosi

Listen Now    Download as mp3 from the show The Science of Vision

Reena - Laser eye surgery is a means of getting rid of your glasses, What we do is reshape the cornea to correct your prescription

Reena - The cornea is made up of three layers. There's the epithelium layer, then we have the stroma which forms the core of the cornea. And the endothelium which is a single layer of cells which provide the nutrients to the cornea. It's mainly made of collagen. The stroma is, anyway.

Ben - So it's a collagen structure but we can reshape it using lasers. How do the lasers actually reshape it?

Slit lamp image of cornea, iris and lens.Reena - They, basically by removing small amounts of tissue. If you were to imagine the cornea as being like a wood - imagine changing the shape of the wood so it's the same sort of thing. All the laser does is cause a small change in shape of the cornea and those small changes in shape can actually give a big change in the refractive power of the eye. Contrary to common belief 2/3 f the power of our eye is actually from the cornea and not from our lens. We can actually do quite a bit by changing the power of the cornea.

Ben - I know that there are a few different types of laser eye surgery. What are the different kinds?

Reena - Essentially there's two basic types of laser treatment. First of all is the lasik which is spelled with an 'i-k' and the other one sounds exactly the same but is spelled with and 'e-k' - Lasek. The difference between the two is just the surgical procedure's slightly different. With the lasik, if we were just to imagine our cornea as being made up, say of 100 sheets of paper you can think of it as what we're going to do is lift the top ten sheets, do the laser treatment underneath and then put those top ten sheets back again. With the lasek - if we imagine the hundred sheets again we'll remove the very top layer, do the laser treatment underneath that and the top layer regenerates. The main difference between these two is in the initial recovery period. Lasik is the one with the faster recovery. Most people are driving standard to better the next day whereas lasek is roughly a week or so behind.

Ben - Why can't you just operate with the laser directly on the surface?

Reena - The top layer of our eyes is the epithelium which is like a skin layer so if you laser on top it will just grow back again.

Ben - Is everybody suitable? Can everyone have laser eye surgery?

Reena - Unfortunately not which is why we do the consultations. Most people are suitable. We have to turn away about 15% of patients who do come and see us unfortunately. It could be a number of things. It could be general health which is a contraindication. It could be the corneas are too thin, it could be the corneas are too steep, too flat. There's a number of reasons.

Ben - What are the risks?

human eyesight two children and ball normal vision

Human eyesight - two children and ball with myopia short-sightedness

Reena - The worst case scenario is an eye infection but that's quite rare. You have the same risk factor every time you put a contact lens in your eye. The most common question I get asked is 'has anyone gone blind from this procedure?' And we haven't had anyone that's lost their sight. If we're thinking about the anatomy of the eye itself you can see why. You rule out a lot of the complications because you don't enter the eye to do the treatment. The treatment is very superficial. You're lasering the cornea.

Ben - Once you've had the surgery how long does it last?

Reena - The treatment itself is permanent. The way your eyes change is individual to yourself. If you didn't have treatment and five years down the line your prescription was going to change by + or -1 for example, this change can still take place. What the treatment does do is it corrects you at this moment in time with the prescription you have now. If your eyes are going to change they're going to do so regardless. A good indication that you're going to be stable after treatment is how stable you are beforehand. If your prescription's been stable for the last 5-10 years then that's a good indication it should be afterwards.

Ben - I've just had a consultation with you. Can you take me through the different stages and what we had to do? Most of it was very similar to a normal eye consultation.

Reena - That’s correct. We have your prescription. We check the health of your eye. We go through your history and symptoms so we know more about your general health. We look at the front surface of your eye, the cornea, the lens and your retina. These are all the things they’d do in a normal eye test as well. Then you had a session where you did some scans. We looked at the front surface of your eye. We mapped your cornea, corneal topography and then we measured your aberrations, how much glare you suffer from.

Ben - I have my scans here and how do I look? Can you tell me what these actually mean?

Reena - First of all if we have a look at the orb scans which is a topography map. First of all, is looking at how steep or flat your cornea is. Yours if perfectly within the normal scale. Having a look at your corneal thickness map your corneas are nice and thick which is fantastic when it comes to laser treatment.

Ben - Map is really the right word. It genuinely looks like a map of hills or mountains and lakes.

Reena - Yes, it does!

Ben - So that’s the orb scan showing the topography of my cornea. What’s the other scan that they did?

Reena - The other scan is the aberrometer. That measures how much glare you suffer from. If you imagine this as being a pinpoint of light what we have here is a picture of how your eye scatters the light in different directions.

Ben - What this should really be is one solid pinpoint of light. It actually looks like a crystal. It’s triangular, lines inside it: like you would on a diamond.

Reena - It does. Everyone has a different map depending on how much aberrations and how much aberrations you have.

Ben - Putting all of this together, looking at my prescription and the thickness and shape of my cornea am I eligible, could I have laser eye surgery?

Reena - Yes, you are suitable to have the treatment done.

Ben - What's the cornea actually made of?

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