Orthokeratology

Orthokeratology (also referred to as Ortho-K, Overnight Vision Correction, Corneal Refractive Therapy and CRT), refers to the use of gas permeable contact lenses that temporarily reshape the cornea to reduce refractive errors such as myopia, hyperopia and astigmatism. This method can be used as an alternative to eyeglasses, refractive surgery, or for those who prefer not to wear contact lenses during the day. Orthokeratology is most often used for candidates with up to -6.00 diopters of myopia, though exceptions may be made if the prescription is only slightly lower (e.g. -6.25). Orthokeratology (also referred to as Ortho-K, Overnight Vision Correction, Corneal Refractive Therapy and CRT), refers to the use of gas permeable contact lenses that temporarily reshape the cornea to reduce refractive errors such as myopia, hyperopia and astigmatism. This method can be used as an alternative to eyeglasses, refractive surgery, or for those who prefer not to wear contact lenses during the day. Orthokeratology is most often used for candidates with up to -6.00 diopters of myopia, though exceptions may be made if the prescription is only slightly lower (e.g. -6.25). Doctors discovered the reshaping phenomena of glass lenses as early as the 1940s. This history of orthokeratology includes contributions made by multiple authors to the use of contact lenses for myopia reduction. George Jessen created what was probably the first orthokeratology design in the 1960s made from PMMA material, which he marketed as 'Orthofocus'. These early designs had generally unpredictable results, leading to the belief that applied orthokeratology was more art or luck than science. Many groups and individuals claim to have been the first to develop modern orthokeratology solutions. However, Dr. Richard Wlodyga, Dr. Philip B. Hanisch and Nick Stoyan, in particular, are generally credited with developing the first reverse zone lens design in the 1980s. However, it was not until computerized corneal topography became available during the 1990s that it became possible to apply the theory to create designs with repeatable results through being able to accurately map the surface curvature of the cornea using a non-invasive, painless imaging procedure. Additionally, the development of new base materials for rigid gas permeable lenses which provided much higher levels of oxygen permeability opened up the possibility of orthokeratology becoming an overnight procedure rather than being used for daytime wear alone. Finally, the introduction of computer-controlled precision lathes meant that lens designs could be manufactured to sub-micrometer levels of accuracy thereby offering the prospect of high volume production becoming commercially viable.