Basically, stay off contact lenses as would be advised by your LASIK surgeon before you have any evaluation done. This is usually anything between 3 and 7 days for soft contact lenses and longer (14 days) if using hard contact lenses.
It is very much up to your surgeon to perform a thorough eye evaluation to determine if and when would be the optimal time for your surgery depending on your eye results and conditions.
Generally speaking, I try not to use measurements older than 3 months for the purpose of treatment. Though this is not a absolute rule and different surgeons may have different norms of practice.
