Therapy With Orthokeratology Lenses
Contact lenses were mainstreamed in the early 1960s with the introduction of Polymethylmethacrylate (PMMA) lenses to the market as an alternative treatment for blurry eyesight. These lenses are known historically as “hard” lenses. At the time PMMA lenses were introduced to the market, the only corrective option for millions of people was eyeglasses. A few years after the introduction of PMMA contact lenses, patients were reporting some interesting experiences; some noted that they could see for a period after they removed theircontacts without the aid of glasses. They might wear their contacts all day and remove them to go to a cocktail party or such. Doctors noted that in some cases progressive myopia slowed down in people who had repeatedly year after year manifested increases in prescription. Doctors discovered that lenses that were fit flatter than the curvature of the cornea were the reason for both phenomenon, so they started purposefully fitting the contact lenses flatter. The results were dramatic in some cases. People with generally less than a certain amount of prescription could remove lenses and see, sometimes for an entire day. The resulting corneal reshaping therapy was called orthokeratology, or orthoK for short. While interesting and helpful for many patients, PMMA material is not permeable to oxygen, so there were some inherent risks in extending wear of these orthokeratology lenses (ortho k lenses) to achieve the desired effect. Also, fitting them to achieve the desired effect was an arduous and inexact science.
In the 1970s plastics for contact lenses were developed that had a higher permeability to oxygen. The flourosilicon elastomers proved safer and healthier corneal refractive therapy for the eye and reduced the risks of orthokeratology, but fitting these lenses was still challenging for doctor and time consuming for patients.
In the 1990s plastics were developed that reached a new level of oxygen permeability. These “hyper-permeable” lenses made sleeping in gas permeable contacts much safer. In the late 1990s, a company also developed a lens shape, known as “reverse geometry” that greatly increased the ease of fitting and success for orthokeratology patients. Combining the healthier materials with the reverse geometry dimensions, orthokeratology is now mainstream. It provides excellent vision sans glasses or contacts for thousands of people worldwide. Studies have been performed that demonstrate the safety and efficacy of the procedure, and other studies have been performed that demonstrate that orthokeratology is successful at managing myopic shift, providing the only known way of providing myopia control for contact lens wearers.
Options such as OrthoK, cornea refractive therapy including paragon crt (vision shaping treatment) are particularly helpful when seeking to improve eyesight in children, and reduce change in vision, specifically myopia in children and may, in some cases reduce the risk of children with myopia advancing to high myopia.