Wearing contact lenses for an extended period of time will result in changes to the front part of the eye (cornea).
Before the pre-LASIK assessment, patients are advised to lay off contact lens wear for a period of 3 days to 1 month depending on the type of contact lens they are using. This difference is due to the rigidity of the contact lens material.
At my practice, I will advise my patients to stop soft contact lenses (toric/non-toric) for at least 3 days and hard lenses (RGP) for at least 14 days.
From my past experience, I personally find that 3 days (for soft contact lenses) is enough for the cornea to return to its original state. However, if during the assessment, I detect any possible corneal changes, I will then advise my patient to stop contact lens wear for a longer duration before re-evaluating.
If your surgeon does not detect any corneal abnormalities during the initial evaluation, it is most likely that the results are accurate.