This question deserves a good answer because it is such a common concern for people looking into the idea of LASIK. If you’ll allow me though, before I answer, let me get one thing off my chest. The ubiquity of this concern is wildly incommensurate with the amount of risk LASIK poses in causing halos. You’d think that everyone gets some halos and that some unfortunate, picked-at-random patients end up with terrible halos so bad that they can’t drive a car at night. This isn’t true.
A LASIK Urban Legend
The urban legend about LASIK halos started the way all good urban legends do. There is an element of believability to it and an even smaller element of truth. The truth is that LASIK was much different when it first debuted. It was a much less accurate treatment over a much smaller area of the central vision. So people often saw lights at night with halos around them. It was when their pupils were bigger than the central zone treated with LASIK (see some stories here). Some of the focused light was in the center and a big ring of unfocused light was around that. And very rarely, it caused terrible halos that left people with genuinely horrible night vision.
Technology improves with time, however, and we don’t have to deal with the same type of issues with LASIK that we did 20 years ago. As an example from more familiar territory, TVs were a foot thick and weighed a kajillion pounds 20 years ago. Taking a picture with a cell phone was reserved for only for wizards 20 years ago. LASIK changed too. We know a lot more about who is a good candidate for LASIK now. And the laser is so much more sophisticated that people with large pupils have no increased risk of halos.
Why do some eye surgery patients experience halos?
Okay, I agree, that was a lot to get off my chest. I think we’re both surprised at how much more I had to say about that than expected. So at this point, you deserve an honest and informative answer on why some patients may have mild halos for a few months. Mild dryness of the surface of the eye causes halos at night, and neuroadaptation (your brain becoming fluent with your new eyes) takes some time.
In my experience, patients who experience halos with modern LASIK surgery have a very mild version compared to even the best outcomes from back when halos became famous. I can’t remember ever seeing a patient experience newer LASIK technology and go on to have bad halos or problems driving at night. In the short term, the occasional mild halos from dryness are treated with artificial tears for a couple months. And neuroadaptation is easy enough because the treatment is to use your eyes to look at things.
All in all, the reason halos come up in conversation at all anymore is because it was a common problem at one time that became very uncommon as technology progressed. No one asks if their TV will be as heavy as a car or if their cell phone will have a camera because these things are familiar now — plus you can just go look at one in the store. It makes sense that people still wonder this about LASIK (here are some myths BUSTED), though. The technology is more mysterious and unknown, for sure. And that’s good soil for any urban legend to grow.