I had fairly strong lenses : -15 and -13 diopters. I have no idea where my vision landed on the 20/xx scale, as I couldn't even see the chart without glasses.
Lasik was not an option at my level - too much material would need to be ablated, leaving me with ... structurally unsound corneas.
I was fortunate enough (!) to develop cataracts 30 years early. One became annoying when driving at night, which tilted me on the necessity-scale from cosmetic-surgery level to medical-necessity level. Only one eye was really bad enough to be an issue, but my correction was so strong that it was also deemed necessary to do the other eye to avoid the large difference in apparent size of objects.
Three side-effects of the cataract removal and lens implant surgery:
1. I now need reading glasses - they are no longer optional, as I have absolutely no ability to change focal distance. I could have gone with monovision, but didn't want to chance tolerance issues. As I am mid-forties, and was already wearing progressive lenses, this is fairly minor.
2. No more "coke bottle". The implanted replacement lenses are ordered just like a basic soft contact lens, with a certain amount of spherical correction, just enough to cover the -15 and -13 diopters my glasses or contacts used to cover. Now that I'm no longer looking through thick concave lenses perched in front of my face, everything appears noticeably larger.
3. Minor starbursts from very bright point sources of light.
You might notice that only #3 is a negative side-effect.
I still wear glasses, but for a minor amount of astigmatism, reading, and a couple diopters of prism (slightly cross-eyed).
I can now get out of bed, see the alarm clock, find my way to the bathroom, etc, without glasses. I can lose my glasses and not be almost completely helpless. I can get by with a cheap pair of readers from the dollar store in a pinch.
Hell, the other day I swam in the sea, able for the first time to see the shore, other swimmers, boats, birds, etc.
Happy? Oh hell yes.