Hi there! I had my procedure done 5 years ago, when I was 26. I had been in glasses since 2nd grade, contacts since 7th, and had a -8.75 prescription in both eyes. I had an excellent experience and couldn't be happier with the results -- I hope it is the same for you!
I just wanted to respond to your question about valium... I was so nervous and excited (mostly excited over the prospect of restoring sight to the blind.. hehe) that I gladly accepted the valium. I swear I must have been completely immune to the effects because I felt as keyed up as ever when they called in me the room. I was lying there in the chair trying so hard to keep still and to keep my eye on the flashing red light, that I felt like I was looking everywhere BUT at the light. Partway through, my surgeon stopped and put his hand on my shoulder and said hey, you're doing fine, just take a deep breath and relax! I swear, someone tells me to remain perfectly still and I get all squirmy, I can't help it!

Anyway, I must have done just fine because I've had 20/15 vision in both eyes ever since. I thought the valium would at least help me rest after the procedure too, but no, I could not stop looking at everything and marvelling that I was seeing so clearly with my own eyes

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So anyway, I say go for the valium.. can't hurt, and it's not going to knock you out or anything. Good luck to you, and let us know how it goes!