- Those who require the greatest vision correction, measured in diopters, are most likely to have ongoing problems with glare and halos because of the steep drop-off between the altered and unaltered areas of the cornea. For that reason, people with myopia exceeding minus-12 diopters, or farsightedness of more than plus-6 diopters, are often discouraged from undergoing Lasik. Or, they can opt for having one or more Lasik treatments that will improve their prescription, but don't attempt to achieve 20/20 vision.
- At present, surgeons' calculations of how much corneal material to remove are based on statistical averages of all patients with a given set of eye characteristics. They yield very good educated guesses, but can't take into account minor idiosyncrasies in individual eyes, and 5 to 10 percent of LASIK patients require a second procedure to refine their vision correction. However, a computer scanner that actually maps a patient's eyes to plan the corneal correction is in development, so a more precise, custom Lasik procedure could soon become the standard.
- Finally, LASIK can't prevent the inevitable. As we age, the lenses in our eyes lose elasticity, just like our skin, and their ability to focus declines, a condition called presbyopia. So, most patients over 40 are still likely to need reading glasses after LASIK, and even if a younger person achieves perfect vision, it won't last forever.
A good doctor will offer all the above caveats to a patient seeking LASIK. "When patients come for an examination in our office," Moadel explains, "they're basically given a very thorough examination, however, the most important thing we do for our patients is educate them. That's critical to a patient, to understand what this procedure can do for them, the limitations of the procedure, and we determine whether or not they should have it done. About 20 percent of people that come to our office are not good candidates for this procedure."
LASIK cannot correct vision problems caused by defects in parts of the eye other than the cornea. Among the other conditions that would preclude LASIK are pregnancy, nursing, pre-existing eye diseases such as herpes, as well as diabetes or immune disorders that would hamper the healing process. Just as a qualified ophthalmologist will screen patients, you should screen doctors carefully if you're considering LASIK.
Find out what kind of training the doctor has had — a year-long fellowship is preferable to a weekend seminar. Ask how many of the procedures the doctor has performed. One study showed considerable drop-offs in surgeon errors after 600 operations, so the more experience your doctor has the better. And don't be afraid to ask how many of that doctor's patients have worse vision following the operation — for the best Lasik surgeons, the figure is 5 in 1,000 or fewer.