Since eyes almost always get worse over the decades starting at age 40, people rightfully assume that they will have to get new glasses every couple of years. It is part of the inexorable decline in vision. So when people ask if their eyes will continue to get worse after cataract surgery, or if cataracts can grow back, it is a good question. The answer is that if the eye stays healthy then then the vision will stabilize permanently after cataract surgery. And cataracts never grow back.
The key to the answer is that almost always the cataract -- the cloudy lens inside the eye -- is the cause of the decline in vision. The lens loses focusing power and clarity and so the glasses have to be continually changed to compensate for that. Once the cloudy lens is replaced by a perfectly clear artificial lens (made of acrylic or silicone), it will not change. The one thing that has been getting worse is now not only completely better, but it will stay that way.
When I say "cataracts never grow back" I should clarify one thing. The new, non-changing lens that is put in the eye is placed specifically in a capsule in the eye that held the old cloudy lens. We do that so that the new lens will sit right where the old one did. In about 50% of cases, if you look close enough, you can find a little bit of cloudiness to that capsule at some point between 3 months and 30 years after the surgery. This is cleared by a 30 second laser procedure that is covered by insurance. People refer to it as "second cataracts" which is incorrect and confusing, but either way it is easily fixed one time and then never has to be fixed again.