Most of the required refractive change was probably completed with the first surgery, but because the first surgery did not achieved the desire result, you now need a small amount of additional change. It is not unusual to follow with a second surgical procedure after the first has stabilized. This additional procedure is called an enhancement.  If the original surgery was Lasik, it is highly likely that the doctor will lift the original flap and apply more excimer laser energy underneath.  This eliminates the possibility of flap creation complications.

Since smaller changes tend to be easier to accurately predict, you should be able to expect a good outcome.  You do need to be patient though.  Fluctuations in vision can last several months.  You want to wait until your eyes have settled down before having an enhancement.  Most enhancements are performed between three and six months after the first surgery, but can be performed earlier and much later.

Discuss the probabilities with your doctor before you proceed.