Orthokeratology ( Ortho K for short ) is the progressive use of hard contact lenses to re-shape the cornea. This is an effective and undetectable treatment for farsightedness. It does nothing for nearsightedness or astigmatism. I know someone who got into the U.S. Air Force using this technique.
With so many people now using the laser eye surgery Ortho K has dropped in popularity but there are still some practitioners.
Hope that helps,
Typhoonpilot