Success depends on several factors, the most important being the degree of nearsightedness, farsightedness or astigmatism. Depending on the prescription, the surgeon can help determine the likelihood of reaching 20/40 or greater vision. Approximately 95 percent of eyes treated with LASIK reach 20/40 or better vision with one procedure, which is the requirement for driving legally without correction. If a patient does not achieve his or her goal with one procedure, additional correction often improves their vision to a satisfactory level.