What causes halos post lasik?

Large pupil: If the patient has halo with contact lenses then he/she may have halo after lasik surgery. Patients with a large pupil tends to get halo with contact or post lasik surgery. The reason is there corrected or treatment zone is smaller than there pupil size in the dark. Its important to check the pupil size before surgery in the dark.

We don't always know: Sometimes a perfect candidate for surgery gets halos, just because we have altered the natural shape of the cornea. We don't always know why halos occur!