Types of lenses used in Orthokeratology
In the United Kingdom, the treatment is currently offered for corrections from +3.00 to -6.00D, with possible treatment up to -8.50D. Some patients may not be suitable for treatment. The US FDA approvals are for procedures up to -6.00D. Some patients with higher degrees of myopia are successfully treated by specialty practitioners with “off-label” uses of these same lenses.
Orthokeratology lenses are made by several companies, using one of two FDA approved technologies. All use special gas permeable lenses to reshape the cornea. The lens material is important for maintaining eye-health during the treatment.
Paragon Vision Sciences manufactures a lens trademarked the CRT (Corneal Refractive Therapy) and marketed as “Accelerated Orthokeratology” (AOK). Bausch & Lomb’s “Vision Shaping Treatment” offers the choice of four approved designs that may only be fit by certified practitioners. The four designs in the VST portfolio include (alphabetically) “BE Retainer” backed by BE Enterprises Inc, “Contex OK-E System” backed by Contex Inc., “DreamLens” backed by Dreimlens Inc, “Emerald” backed by Euclid Systems Corp, and “Fargo” backed by C&E GP Specialists.
Only a few other brands of ortho-k lenses have been approved by the FDA for overnight wear. Currently no other studies are underway for any other lens designs.
Orthokeratology has occasionally had severe side-effects, even blinding complications . These often occur due to the patient’s failure to follow appropriate hygiene, and the use of tap water to rinse or store. Complications may also be due to relative corneal hypoxia (lack of oxygen) with prolonged or overnight contact lens wear in lenses made from the wrong material. The use of high or hyper oxygen permeable materials significantly reduces hypoxia, and are usually the materials used in Orthokeratology.
The idea of correcting vision by reshaping the cornea has been around for a while. Doctors discovered the reshaping phenomena of glass lenses as early as the 1940s. George Jessen created what was probably the first orthokeratology design in the 1960s made from PMMA material, which he marketed as “Orthofocus”. The idea of correcting vision by reshaping the cornea has been around for a while. Doctors discovered the reshaping phenomena of glass lenses as early as the 1940s. George Jessen created what was probably the first orthokeratology design in the 1960s made from PMMA material, which he marketed as “Orthofocus”