Most patients experience dramatic improvement in how well they can see without eyeglasses or contacts. Estimates vary, but studies indicate that well over 50 percent of patients who undergo laser eye surgery achieve 20/20 or better, and over 90 percent achieve 20/40 or better (good enough to drive without corrective lenses). Surveys indicate that more than 95 percent of LASIK surgery patients are satisfied with the results.

But there is still a chance that laser eye surgery might not completely correct your vision so well that you no longer need to wear lenses. The odds of surgical success in terms of vision correction depend on your specific error—particularly the severity of your error—and other factors.

If you have only minor error, and especially if you are nearsighted, your chances of success are the highest. For persons with farsightedness and farsightedness with astigmatism, chances of success are lower; if you have a high degree of farsightedness along with astigmatism, the results are the least predictable.

When the initial correction from LASIK is insufficient, some patients undergo a second surgery. But re-treatment won’t always solve the problem, and, in some cases, re-treatment is not possible (particularly if the surgeon has removed too much corneal tissue).

What’s more, visual acuity as measured on an eye chart is not all you care about. A 20/20 measurement means that from a distance of 20 feet the smallest print you can read on a standard eye chart is the same size as the smallest print someone with “normal” eyesight can read. (A 20/40 measurement means that at 20 feet you can read only what a person with normal eyesight could read at 40 feet.) But the ability to read an eye chart is not the same as having it look right. You might be able to read small letters even if both they and the large letters look fuzzy or wavy. Unfortunately, that’s what some laser eye surgery patients experience.

Other problems with post-surgical vision include—

  • Seeing glare, especially at night;
  • Seeing halos and starbursts around lights at night;
  • Seeing too little contrast in dim light;
  • Loss of lines of vision—some lines simply not visible on the vision chart; and
  • Dry eyes.

Although such problems usually disappear after the first few months, for a very small percentage of patients they persist—and in some cases are uncorrectable.

Other problems, although rare, are infections or growth of surface-type cells under the repositioned flap or on the reshaped corneal tissue. Fortunately, most of these problems can be treated if discovered promptly through proper follow-up care, and usually just cause discomfort and extend the healing process.