The best place to start is obviously the careers office, they will have the latest info with regard to medical requirements, I am fairly sure that when you start aircrew training your eye sight has to be 20/20 without corrective lenses!
If your eye sight is acceptable you will need to pass aircrew selection, this is a bunch of mental agility and physical coordination tests, make sure your mental arithmetic is up to scratch, lots of speed, distance, time questions, they say that practising computer games can improve you coordination skills.
As well as aircrew tests you have to pass the AIB this is most peoples stumbling point< they are looking for Officers, so you must demonstrate, leadership skills, mental agility, intelligence, a knowledge of current affairs and all round sound character ( I really don't know why, I have met very few officers with any of these skills!!!!!!)
At the AIB you are required to carry out a multi-stage fitness test (bleep test) to your limit, so basically be as fit as you possibly can be, I would suggest at your age you need to be achieving around level 12 minimum or running a mile and a half in less than 9 minutes. RN fitness test gives you around 11 mins I think.
Hope this helps, but you really need to visit a careers office.
The fitness thing is just my estimate, you don't need to be superman but you do need to look like you have put the effort in, I am a "little" older than you and I get 12.35 mins to run the mile and a half, it takes me less. When I did my Senior rates leadership course I was 35 I did it in 9.04 mins and I wasn't the fastest there.
The AIB is not looking for commandos, they are looking for people with potential, it's just down to you to show them you have potential, preparedness is definitely a good start point. You wouldn't want to bang out of your fitness test at around the 7-8 mark......this is the level expected of a 40 year old!
your eye sight may not be a problem, you need to speak with careers service guys.
I may be wrong here but doesnt the eyesight thing depend on what you want to fly, ie fast jets perfect no glasses, rotary corrected eyesight or something like that.
As chieftiff said check with the recruiting office rather than trust forums mate, they will have the latest facts and figures however be prepared to take some serious crap when you first join as a Young Officer. You wont be kicking the tyres and lighting the fires for a little while.
Don't forget the requirement for enhanced social skills, looking good in shades, being able to hold a tan better than most, ability to live in hotels whenever the ship is within 1000 miles of land and swagger, lots or swagger! :lol: