I'm not sure about the Army, but I went to apply for the Royal Marines last year to be told I was borderline S3 (blind as a bat) -4 in each eye. I decided to go the laser surgery route and was given the Navys policy on Laser surgery, which is that LASEK and PRK are acceptable. You have to wait one year after having this surgery before you can start the application process.
LASIK is classed as an invasive surgery and the flap created by the laser (intralase) or blade will never correctly heal. You should not consider this surgery if you are considering the armed forces or play an impact sport such as rugby/martial arts. LASIK is detectable.
LASEK would be my suggestion if you intend to go through with the surgery. I did significant research into outcomes and LASEK produced much better results.
The flap created during LASEK surgery will also completely heal as no cut is made to the eye, the front of your eye is scraped off after alcohol is applied to losen the fleshy bit. I bricked it when they did this.
I was also informed that once the eyes have healed, LASEK is pretty much completely undetectable.
LASEK takes longer to heal and a couple of hours after, you're in a bit of pain. But if you're going in the army you can take it.
The exact surgery I got was Lasek with wavefront from Ultralase (avoid the budget surgery, it's not worth going through a less reputable firm just to save a few pennies).
I had the surgery about 7 months ago and my eyesight is slightly better than 20:20 now. I chose to wait the year rather than blag it for the following reasons. I was told that if they find out you've had the surgery and not declared it, you could be immediately discharged. I also felt like I would be constantly lying and unfortunately I'm far too honest. Finally it cost me £3k so I needed a year to pay it back.
If you are going to blag it I'll make the following suggestions.
When you go for the surgery, they'll ask you for your current doctors details. Just say you don't have one at the moment. If you give them the details, they will contact them and the surgery will be put on your medical record, which I believe the army look at during your application.
If you get LASEK which I strongly suggest, I'd wait three months after having it done before applying. I found it took about 6 weeks for my eyes to go back to normal and even then they felt funny when I was doing jujitsu or weight training.
Make sure you fully aware of the armys stance on the surgery.
Sorry bit of a rant, but I hope this helps.