Orthokeratology or Ortho-K is a non-surgical process which reshapes (flattens by compression) the cornea of the eye using contact lenses to reduce refractive errors (nearsightedness and astigmatism). Ortho-K uses reverse geometry contact lenses. Flattening the cornea reduces the focusing power of the eye. Since the amount of corneal flattening can be accurately controlled, it is possible to bring the eye into correct focus and compensate for the refractive error. After the contact lens has been removed, the cornea retains its flattened shape for part or the entire remainder of the day.

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 generally provided 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. But Dr. Richard Wlodyga, in particular, is generally creditedwith developing the first reverse zone lens design in the 1980s.

However, it was not until computerised corneal topography (mapping of the contours of the cornea) 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 (manufacturing cutters) meant that lens designs could be manufactured to sub-micron levels of accuracy thereby offering the prospect of high volume production becoming commercially viable.  A significant milestone for the US market occurred in June 2002 when the FDA granted approval for overnight wear of a type of corneal reshaping called “Corneal Refractive Therapy” (CRT).

Orthokeratology involves first measuring the refraction ofone’s  eye which will indicate to the optometrist the degree of nearsightedness, farsightedness and astigmatism  that one  may have. Next it will be necessary to map the shape of the front surface of the eye using a corneal topographer. Based on the digital map of your eye and the amount of your prescription to be reversed, the optometrist will develop an exact shape and set of parameters necessary to prescribe in order to obtain the desired effect on your corneal shape. The special contacts are manufactured to exact specifications for your eyes. They will initially be worn for about 8 hours daily until proper correction is achieved and your vision is improved. Sometimes, your optometrist will actually prescribe a wearing schedule whereby you will only need to wear the lenses while you sleep. After that, the lenses may only need to be worn a few hours a day or at night for about 3 days a week to keep the cornea in the shape necessary to allow you to see clearly. The exact wearing schedule really depends on your eyes and correction and will be determined by your optometrist. Upon removal of the lenses you will be able to obtain improved vision without any corrective lenses. This is a great alternative for those who are too young to consider LASIK, those whose prescriptions are continuing to change and  it is especially useful for youngsters and teenagers involved in sports where wearing contact lenses might be limiting their sports activity. A new type of lens and material actually allows accelerated ortho-k that can produce results in days rather than months.

Retha van der Walt

B.Optom (RAU) FOA (SA)