Thinking about LASIK eye surgery? There's a lot to think about.

Humans are essentially visual creatures. The thought of someone interfering with our eyes is difficult to bear for any of us. But millions of people every year have what, at first sight, seems like a highly invasive technique on their eyes. Why do they do it? For centuries we've struggled with spectacles for vision correction. Everyone knows that they're not really the answer. Then came along contact lenses. And when breathable, extended wear lenses came along, we thought they were the pinnacle of ocular technology. Not any more. Now we have LASIK - Laser Assisted In Situ Keratomilieusis - using a computer controlled micro laser to remove parts of the cornea and reshape it for a considerable improvement in vision. But for something as valuable as our eyesight, it's clearly imperative to consider all the implications. Here are just a few to think about:

LASIK may not give you perfect vision. The American Academy of Ophthalmology (AAO) reports that seven out of 10 patients achieve 20/20 vision, but 20/20 does not always mean perfect vision. If you have LASIK to correct your distance vision, you'll still need reading glasses around age 45. You may need additional enhancement surgery to give you the best possible vision after LASIK. You should be at least 18 years old (21 for some lasers), since the vision of people younger than 18 is usually still developing. You may be a candidate for monovision (correcting one eye for distance vision and the other eye for near vision). If you can adjust to this correction, it may eliminate or reduce your need for reading glasses. In some instances, surgery on only one eye is required. You may experience a decrease in contrast sensitivity, "crispness," or sharpness. That means that even though you may have 20/20 vision, objects may appear fuzzy or grayish. Your vision probably will be blurry the day of surgery, but it will improve considerably by the next day when you return for a follow-up exam. If you wear bifocals or reading glasses you will need glasses for reading after LASIK. LASIK cannot restore the flexible (back and forth from distance to near) focus of youth.

It's possible, though unlikely, that you may have corneal scarring, irregular astigmatism and an inability to wear contact lenses. Your optometrist will measure the curvature of your cornea and your pupils. You may be rejected if your pupils are too large. She'll also measure the topography of your eyes to make sure you don't have an irregular astigmatism or a cone-shaped cornea and the the pachymetry, or thickness, of your cornea. You need to have enough tissue left after your corneas have been cut and reshaped.

As you can see, there's a lot to think about, not least the cost, which currently is about $1700-2000 per eye. Talk it over with you optometrist and above all don't feel pressured by anyone into having LASIK, they are your eyes after all.

Mike Thompson writes on a wide range of subjects and runs www.lasik-laser.com he's been involved with laser eye surgery since it was developed.