Feel the burn (November 2007) by Paul McNally
Do your eyes need surgery?
Set your sight on the target, even if that means a laser aimed at your eyeballs
The tissue equation
Laser surgery starts as a question of tissue. Do I have enough? How much do I need? What are they going to do with it, exactly?
“The average tissue spare on someone’s eye is 500 to 600μm (micrometres),” says Aleksic. For the cornea to be stable after the procedure you need 250μm to be left untouched. How they assess your tissue count is futuristic. They map your cornea in a corneal topographer (of course) – which looks like a hypnotist’s umbrella.
The reading pops out like a geographical heat map. This will form the basis of Aleksic’s game plan during surgery. It will reveal if you have astigmatism – which means your focal point is scattered and can only be operated on under certain circumstances. It’ll also say, in an ideal world, what shape your cornea should be.
It’s not much, after all: a thousandth of a millimetre. So with that spare tissue: approximately 15μm of tissue needs to be shaved off for each optical unit (dioptre) that needs to be corrected. If your eye is - 6.00 dioptres, then you’re going to use up 90μm of tissue – which equals 60 seconds of laser in the chair.
The reason why glasses even still exist can be understood with one word: infection
This is also where Aleksic gauges if you’re eligible for surgery. Your eyes need to be tested today and then again in six months time, so there’s no drastic difference. Legally you need to be 18, but it might take till your mid-twenties until your prescription settles.
If you’re too blind for the tissue available, you can’t reach perfect vision. The flap uses a lot of special tissue so if you’re short of this vital tissue it’s possible to use a different procedure involving a thin flap or rubbing away the first layer of cornea with a brush. But a drawback is that the healing process is much slower. It may take close to a week for your vision to stabilise. It has to heal around 360 degrees, not just across the flap incision.
Alright, what’s the catch?
Chris is done. It’s over. Aleksic takes the cling wrap off his eyes.
“One woman last month – all she was worried about during the laser was having her eyelashes plucked out while stuck on the plastic,” says Aleksic with a grin.
Chris can already see better – not as good as with his glasses yet, but given the standard recovery time, he’ll be able to drive by tomorrow. He’s given a battery of drops and a nurse cellotapes plastic shields to his face, reminding him that the real challenge is still to come. The reason why glasses even still exist can be understood with one word: infection.
The chances of a problem are small – less than 0.1 percent chance of infection, and blindness (especially if infection is properly treated) is even rarer. But this is when your mind starts to do statistical back flips. No one wants to be special, because it’s an operation with so little risk that as soon as you’re special, then you’ve got a problem.
The first rule of laser surgery is don’t touch those eyes. “You don’t want a cornea with a wrinkle in it,” says Aleksic. If you disrupt the healing flap it can get infected, scar and leave you looking through an awkward fog for the rest of your life.
Aleksic pedals out his mobile number for 24/7 contact – an eagerness that’s pleasant but frightening. “If some kid pokes you in the eye, don’t keep quiet about it,” he says. He’ll haul you in and set about repositioning the fl ap. Most infections are sorted out without another go at surgery and with a different battery of drops. If you’re off on safari (like most tourists) and can’t get attention pronto, the problem can escalate.
It’s all fun and games until…
Once you’re out of the infection frying pan you’re into the healing fire. Five percent of people need a laser top-up at a later stage and you could be one of the few, depending on how you heal. If you heal too fast there could be a problem, so the drops help regulate the healing. The healing is completed six months after surgery. But if you have enough tissue – the currency in this world of laser surgery – then you can have your sight fi ne-tuned until it’s perfect.
Another problem is with your night vision. You could get halos around street lights (though most patients only notice this when Aleksic points it out). The only other setback is a feeling that your eyes have just been thrown in the gym. After all, you haven’t used these muscles properly in years.
These are your eyes on laser
The next day Chris drives in for his checkup. He keeps motioning to take his glasses off until he remembers he’s not wearing any. He’s truly gobsmacked, driving is easier now because he has better peripheral vision and, as a bonus, his face is more handsome, free of the thick, black frames.
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