If you are currently lets say -7.00 in both eyes, and only have a cataract in one eye, you will need to choose.
If they correct the cataract eye to plano so you have good distance vision, you will need to wear a contact over the other eye as glasses will cause dizziness/ double vision. You will need reading glasses for up close. You can also choose to have cataract surgery done in both eyes, even though you only have a cataract in one so you have good vision in both eyes and only need glasses for reading.
Or, they can correct the cataract eye to -5.00 or so, meaning you will be less nearsighted than you were but can continue to wear your glasses as you have been. If the other eye then ever develops a cataract, they will correct it -3.00 instead of -7.00 making your prescription smaller, but you still keep wearing glasses.
I read your other post, so I know you are very nearsighted and wear progressives. First quesiton for you would be- would you rather have good distance vision and need glasses for close up only? Or would you rather have good near vision and wear progressives?
If you want your vision to stay as it close to it was when you were born, you can just have the cataract eye set to whatever your prescription was before it shifted nearsighted, or to the same as your other eye. Then keep wearing your progressives. You only need to start worrying about contact lenses and special implants if you want to get rid of the glasses you've been wearing your whole life.