Ortho K is the practice of wearing hard contact lenses overnight to correct vision. While the lenses are in, they reshape the cornea so that when you wake up you can see clearly even without the lenses in.
Ortho K is a great option for people who want to be glasses and contact lens free during the day, in particular people that play sports, work in dusty or dry environments or suffer from intolerance to other contact lenses.
Recent studies have found that Ortho K has the added benefit of slowing the progression of short-sightedness. This would be most suitable for younger patients who have a family history of short-sightedness and/or do a lot of near work. Slowing the progression of short-sightedness reduces the complications of short-sightedness later in life.