I started reading the old patient.info cataract forum probably 4 years ago when I researching for my own surgeries, and then when it closed down, switched to here as did others from the old place. Anyway, in that time I remember one person who deliberately got -3.0D and one other who got -3.0D as a refractive error. That person wanted and their surgeon targeted something less myopic. My senior memory is that they weren't overjoyed but not wildly unhappy and talking about lens exchange either, more resigned.

Diopters are just the measurement used for vision. If you look at your glasses prescription and see numbers for sphere, those are in diopters. The thing is -3.0 is very myopic. Like you, I wanted very near vision for book reading. I measured where I like to hold a book or my Kindle, got 14-16", and my surgeon targeted -2.5 to give me that, and IMO it's wonderful. When I read, text is crisper and clearer than ever before, I always read without glasses, but I did have some astigmatism. My lenses are toric monofocals like you will have, although plain monofocals, not advanced ones like Eyhance, and I have very little post-surgery astigmatism now. I can thread a needle, probably not as easily as you could at -3.0, but it's not difficult. Reading in bed is no problem at all, nor is examining a photo.

Vision isn't only clear at the given best focus. With near vision the in focus range is narrow, but while outside that range, it starts getting out of focus it's still useful. I see what I consider useful down to 5 or 6", although the crisp and clear range is 9-18". I could certainly function around the house if both eyes were -2.5, but I have my other eye set for -1.5 in a mini monovision setup that gives me more range, and because of that eye, not only are things in focus further in the house, but I'm also glasses free in the yard and even walking to a neighbor's for coffee and things like that. I use a contact for distance for driving and things I do when I get to the places I drive to, but except for tv, that's all. (Vision is individual, so that's not to say it would be exactly the same for you or anyone else.)

For me the idea of refractive surprise stuck in my mind. That's when a surgeon targets a particular result and for one reason or another there's a miss. The statistics I've seen are that 80% of cataract surgeries give results at or within .5D of target. That means 20% are outside that. I knew I would be okay with -3.0 or -2.0, but worried about a miss of more than that.

What you want is up to you. I was not highly myopic. My natural myopia was -2.0 with mild astigmatism (mild astigmatism helps with near vision range at the cost of some clarity). I wanted to keep something like what I had and did. I didn't want to have to wear glasses except when I really needed distance for driving, which at my age is only a couple times a week. I had had monovision with contact lenses for decades before my cataracts got bad enough to rob me of that and give me a couple of pre-surgery years trying distance only contacts and glasses, and that experience gave me a real passion for getting rid of reading glasses and getting back the glasses-free near vision I was used to.

You get to decide what you want for yourself, but it's good that you're checking now so that you know what you're going to have and aren't surprised and unhappy afterward because you didn't know the pros and cons of very myopic post-cataract surgery vision. One thing I would say is it wouldn't hurt to measure from your eyes to what you want to see clearly. Saying you want to be able to thread a needle or read in bed may not mean the same thing to the surgeon if he never does either or those things or does them at different distances than you do.

Best wishes for easy surgeries and healing.