You should be able to get a "Ranger contract" at MEPS when you sign with the career counselor. If that happens, Uncle Sugar will make sure you get in the proper physical and mental shape for Ranger School, or if not, you'll be shit-canned.
Not trying to sound harsh, but the standard is either met, or you go "needs of the Army". You will get plenty of ruck-time at Ft. Benning during Basic and Infantry School, then Airborne school has to be done.
Next, you will have to complete RIP (Ranger Indoctrination Program). IF you make it that far, you'll go to your Ranger Battalion, and they will prep you for Ranger school, which you will likely attend once you make PFC.
Don't know about the eye surgery question.
I had a TS when I was regular Army, and I was born in Canada, sooo........
There are plenty of old farts in the Infantry. You'll be ok as long as you are motivated.
Good luck!