I had LASIK surgery 20 days ago. When I am in a bright environment, the quality of my vision is very satisfactory, I just realize a slight loss in contrast sensitivity . However, in environments with low light, I see halos around any bright object, which makes the quality of my vision bad at night. My eye doctor said that it usually occurs due to corneal edema, and which disappears in a period of 1 to 3 months. If I don't have problem with pupil size, what might be causing this problem?