From Wikipedia, the free encyclopedia
Orthokeratology (also referred to as Ortho-K, Overnight Vision Correction, Corneal Refractive Therapy and CRT), refers to the creation of gas permeable contact lenses that temporarily reshape the cornea to reduce refractive errors such as myopia, farsightedness 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. Marketed under brand names like "DreamLite", "OK Lens", "EyeDream", "MiracLens", "DreamLens", "i-GO OVC", "GOV", "Wake and See", "CRT", "Fargo/iSee", "Emerald" and "Wave Contact Lens System", Orthokeratology is most often used for candidates with up to -6.00 diopters of myopia.
Types of Lenses
Orthokeratology lenses are made by a number of companies globally. All use special gas permeable lenses to reshape the cornea. The lens material – and especially its oxygen permeability measured by its 'Dk' rating (the higher the value, the greater the degree of oxygen permeability) – is important for maintaining eye-health during the treatment.
Paragon Vision Sciences manufactures a lens trademarked "Paragon CRT" (Paragon Corneal Refractive Therapy) and marketed as "Accelerated Orthokeratology" (AOK) using base material manufactured in-house. Also under the Paragon Vision Sciences FDA approval is the FARGO lens exclusively manufactured by GP Specialists in San Diego. The Euclid Systems and the other five overnight orthokeratology lens designs offered under the Bausch & Lomb "Vision Shaping Treatment" (VST) portfolio are manufactured by various contact lens laboratories in the US and internationally using Bausch & Lomb base materials and in North America may only be fitted by VST certified practitioners.
The eight designs in the VST portfolio comprise (alphabetically):
- "BE Retainer" backed by BE Enterprises Inc
- "CKR" backed by Eye Care Associates
- "Contex OK-E System" backed by Contex Inc.
- "DreamLens" backed by Dreimlens Inc
- "Emerald" designed and manufactured by Euclid Systems Corporation
- "MiracLens" designed and manufactured by MiracLens,LLC
- "NightMove" backed by Advanced Corneal Engineering Inc
- "Wave Ortho K" by Wave Contact Lens System, LLC
No other design of ortho-k lenses has been approved by the FDA for overnight wear and currently there are no other studies underway for any new lens designs. Non FDA approved designs are available, such as Menicon Z Night which uses fenestrations in the reverse curve to maximize fluid flow while maintaining centration with a high Dk material. Menicon Z material is FDA approved for up to 30 day wear in regular GP form.