Safety and effectiveness are 2 of the most important considerations when trying to make a decision about whether one should proceed with any surgery.
Suffice to say that enhancement years following LASIK is possible but there are some important factors to consider before one can safely undergo enhancement surgery.
A basic requirement would be that there should be sufficient corneal thickness. Another would be that the cornea does not have any other abnormalities. Finally, the rest of the eye has to be in good working order.
Do pay a visit to your eye surgeon to have a thorough eye exam. That way, your eye surgeon will be able to answer the above questions about safety and effectiveness that are specific to your current situation.