Orthokeratology, or ortho-k, is the use of specially designed and fitted contact lenses to temporarily reshape the cornea to improve vision. Most ortho-k lenses are worn at night to reshape the front surface of the eye while you sleep. Vision improvements are reversible but can be maintained if you keep wearing the lenses as directed.Ortho-k is mainly used to correct near-sightedness(nyopia). This vision problem can also usually be corrected by eyeglasses, regular contact lenses, Lasik or PRK . Ortho-k is associated with an increased risk of infection (microbial/bacterial keratitiis). This risk is especially concerning for children and adolescents, who may be less able than adults to maintain good hand and contact lens hygiene .