Ortho-K finds its roots in the first use of PMMA lenses. The lenses were made extremely flat (1 to 2 diopters flatter than the flattest measured central keratometer reading) to ensure that the eyes would tear, and thus the eyes could get oxygen. However, the flat contacts were not comfortable enough to be worn all day, and as such patients would switch to their glasses after a prolonged use of the PMMA contacts. The switch would cause the patient to experience “spectacle blur” which indicated that the patients cornea shape was actually changing with the use of contact lenses. Robert Morrison first studied this phenomenon in 1956. Morrison specifically worked on myopia control, and his study indicated that the 1,000 teenagers wearing PMMA rigid orthokeratology lenses with a fit of 1.5-2.5D flatter than the flattest corneal curvature did not progress in their myopia after two years. Other findings included that curvatures not only remained stable, but in some cases changed for the better. They also found that in some cases refractive errors decreased and unaided visual acuity improved. After these studies were completed, orthokeratology began increasing its use in the 1960s in the United States. The procedure was first known as “Orthofocus” and employed by George Jessen, However, orthokeratology got off to a very slow and rough start. The scientific community was hesitant, because of the belief that altering the curvature of the cornea was not safe. There was also not enough clinical evidence to support that the procedure would not alter the function of the cornea. This minor setback was overcome with the use of corneal mapping instruments. These instruments were a way to scientifically prove that orthokeratology can create a positive change in the corneas of patients. The positive gains of orthokeratology was further proven in several scientific studies.
Some major studies include CLAMP (Contact Lens and Myopia Progression), Myopia Control study in Houston, LORIC (The Longitudinal Ortho-K Research in Children, and SMART (Stabilizing Myopia by Accelerating Reshaping Technique).work conducted at The Pacific University School of Optometry, University of California at San Diego Medical School, The University of Houston College of Optometry, and the University of California at Berkley School of Optometry. These studies show that overtime this technology can cause a reduction in myopia during treatment with a plateau of reduction after a long course of treatment. Reductions in Myopia varied from .3-1.52D in individuals with a 2.5D-4.00D of myopia. Time of treatment can range anywhere from three to ten months, with majority of treatment occurring within the first six months.
These studies also improved the method of orthokeratology into the great method of treatment that we have today. In the past ortho-k lenses were designed as simple rigid contact lenses that fit flat as possible on the cornea while still remaining in an acceptable position. The problem with these lenses was that they would commonly de-center from the required position, which in turn caused corneal distortion which could lead to astigmatism. The other problem was the use of PMMA lenses, which caused corneal edema, which in turn could make the corneal distortion worse. Lastly, the lenses were used during the day and only on occasion, because the lenses were not gas permeable and could not safely be worn at night.
However, these problems were addressed when in 1971, Leonard Seidner and Norman Gaylord developed Polycon. Polycon is the first silicone acrylate rigid gas permeable lens (GP) material. This new material increased patients’ comfort, as the lenses were more permeable to oxygen and made the lenses more breathable. They were improved again in 1989 when Richard Wlodyga and Nick Stoyan developed Advanced Orthokeratology, which meant that orthokeratology could now be completed much quicker then the standard procedure from before. His new method involved making the secondary curve of the lens much steeper than the base curve, which in turn enable the mid-peripheral cornea to steepen much more quickly. with a new lens called Contex OK -3 lens. This new lens called Contex OK- 3 used three different and distinct zones to create a more controlled and profound change of the central cornea. This new lens also decreased the time it took to reduce myopia. The lens offered a prolate shape (steep in the center and flat in the periphery) and moderate curvature. However, even with this new improved lens, centration was still a key issue. If a lens becomes decentered than “induced astigmatism” could become a problem and create double vision and cause the pupils to become larger when wearer drove at night. Even these lenses’ problems were solved with more proper fitting and more frequent lens change. New methods created a change of as much as 1.00 D in two to seven days and could change up to 3.00 D in six months. The lenses used today are vastly improved from the lenses from the start of ortho-k and now cause accelerated change that improves patients lives everyday.