RN Aircrew Aptitude testing Watch
The RAF & RNs eyesight pass mark is 6/6 with no myopia. The Army's I can tell you if anyone is interested, but not off hand.
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how do they test for myopia in the eyes?
In effect, as long as you have 6/6 you're fine for the navy, even if the shape of your eye is slightly out - trust me on this, my housemate went into great detail with Cranwell over being slightly outside RAF limits himself and it generated a lot of paperwork with all sorts of facts and figures!
Oh yeah, one other fact - aptitude scores: for the navy you have to pass pilot and observer, and the navy observer score is higher than the RAF's, I don't exactly know what it is but it is higher than 122 (friend failed with that score - the RAF pass is only 100)