I had my right eye done in October 2017 due to a cataract forming, getting close to not being able to pass the Class 2 medical. The operation went really well, but the CAA insisted on my being grounded for 6 weeks. Apparently, I'd have returned to flight quicker if I'd lost the eye altogether! My eyes were just over -3.5 dioptre in 1982, which was just outside the limit then for Class 1, but they changed the limit about 20 years ago, so I did get a Class 1 in my 50's. Incidentally, My eyes are now -2.5. Incidentally, I elected to have a new lens at -2.5 to match the left one, great for taking my glasses off for reading etc!
My left eye isn't too bad at the moment, so I'm waiting until it is to get it done.
My sister was -6 dioptre and felt really self-conscious as a teen wearing specs and all the faff of contacts all her life. She elected to have new varifocal lenses in her eyes, for which she had to pay as there wasn't anything wrong with her eyes. She's found it completely liberating and can go from close reading to distance viewing without any specs. She's now in her late 60's, no problems.
Now, what you're asking is can you have the latter done and then get a flying medical? Well, the best advice is to find your local Aircrew Medical Examiner and ask them. The CAA have now put all this stuff 'out to industry' so you'll probably not get an answer from them direct.
As we say to all our prospective students, for goodness sake, go and get your medical done before you spend money on flying training. It sounds like that's what you're doing - great!
Good luck
TOO