Many people believe that Lasik can restore their vision to 20/20.  However, this is not always the case.  The fact of the matter is that not everybody is able to achieve 20/20 vision after the surgery.  It is also difficult to find exact statistics as well. 

CorneaTexas.com reports that there is a 96% success rate with Lasik.  According to the American Association of Professional Eye Care Specialists, about 55% of people will have 20/20 after the surgery.  They do report that 92% of patients will achieve 20/40 vision.  By the way, 20/40 is the minimum vision requirement in the US to get a drivers license. 

The AAPECS also reports that in 100 consecutive patients in 1999, 93% of patients left surgery with 20/25 vision or better and 100% had 20/40 or better.  The complication rate was 0.4% and the enhancement rate was 2%.  This means that only 2 people required enhancement surgery after the initial surgery. 

The AAPECS reports that adverse effects and complications are very, very rare but the do occur.  They reported these statistics for adverse events.

11.9% Significant Undercorrection
4.2% Significant Overcorrection
3.5% Severe Halos
3.0% Loss of more than 1 line of best corrected vision
1.9%  Loss of more than 2 lines of best corrected vision
1.7% Severe glare
<1.0% Corneal epithelial flap, Increased IOP, Flap edema, Induced astigmatism