The answer to this is a resounding “sometimes.” As in most of medicine, there is enough variability from person to person that blanket yes or no answers can’t work. This isn’t the same, however, as saying we don’t know if it will probably give you better vision than with your glasses. The “sometimes” in this case is applied generally, not personally.
It’s kind of like asking if people get upgraded to first class when they fly. The general answer would be “sometimes,” but you can get a much more relevant answer if you’re asking the airport person (the one behind the computer? I’m not sure what that job title is) about the flight you are taking that departs in an hour. They can tell you that there are three empty seats in first class and they like the cut of your jib, so yes, they’ll upgrade you. Your personal “yes” is situational unlike the “sometimes” which is statistical. “Thanks, Airline Computerist!” you can say as you walk away to look up the name of their job, which is escaping you at the moment.
In the same way, you can find out how the statistical “sometimes” of super vision applies to your situation. At a good LASIK consultation, the diagnostics analyzing your vision, your eyes, and your glasses can usually provide a much more specific answer on the chances you have to achieve better uncorrected visual acuity than your previous best corrected visual acuity. This UCVA vs. BCVA is an actual measurable data point that is tracked in studies. That’s why it has a fancy, official initialism.
There are two situations that make up the majority of cases where LASIK can best the vision you previously had with glasses. They both have to do with the shape of your cornea (hence the need for diagnostic imaging) because for a decent number of people, the cornea isn’t shaped as ideally as possible. The first group are those who are myopic and happen to be lucky enough to have steep corneas. That means the dome of their cornea is more like the point of an egg and less like the other, flatter side of the egg. LASIK fixes myopia by making the cornea flatter. So in these cases, it makes a steep cornea more “normal.” That can result in sharper vision and better night vision than glasses could provide.
The second situation has to do with astigmatism. Yes, astigmatism is mysterious and vague (or at least it was to me before it became my job), but it is a measurable entity. And I don’t just mean we can measure the amount of astigmatism. I mean that we can measure how much the shape of your cornea is responsible for your astigmatism. For some, the astigmatism measured in the glasses prescription is the exact same amount and degree of astigmatism we find in the topography of the cornea. It’s wonderful when that happens! In those cases, LASIK is able to fix the cause of the astigmatism. That can allow for better vision than glasses, which were just neutralizing the blur with lenses prescribed to have an equal and opposite amount of astigmatism.
There are a lot more factors involved in the nuance of whether you can get better uncorrected vision than your previous best corrected vision. Since this is an article and not a giant textbook, necessity requires the rest of factors remain mysterious until your LASIK consult. That makes it more fun, I think. I’ve never gotten upgraded to first class — I assume it’s because I’ve never asked — but I bet I’d like it that there’s a little bit of mystery as to what the Flight Seating Computerator is typing onto their monochrome screen. In any situation with an unknown, there’s a magic in finding out what happens when statistics crystallize into the features that will involve you.