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Orthokeratology
Cornea
1. Orthokeratology
Exam pearl
- Orthokeratology (ortho-k) is a reversible, non-surgical refractive correction modality in which specially designed gas-permeable contact lenses are worn overnight to temporarily reshape the corneal epithelium. Over the past two decades, the field has evolved from a simple refractive correction tool into a clinically validated intervention for myopia control in children and adolescents. This review consolidates current knowledge spanning corneal biomechanics, lens design principles, clinical efficacy, patient selection, safety profiles, and emerging research frontiers.
2. Introduction & Historical Background
Origins of Orthokeratology
- Orthokeratology traces its conceptual roots to the mid-20th century when practitioners first observed that wearing rigid contact lenses could produce transient refractive changes.
- George Jessen is widely credited with describing "orthofocus" in 1962, a technique using flat-fitting PMMA lenses to intentionally flatten the central cornea and reduce myopia.
- Early practitioners worked empirically, with limited reproducibility and inconsistent outcomes.
Evolution of Lens Technology
- The pivotal technological leap came with the introduction of reverse-geometry lens designs in the 1990s.
- Unlike conventional lenses, reverse-geometry lenses feature a central optic zone fitted flatter relative to the central cornea and one or more steeper secondary or reverse curves.
- These curves help stabilize and centre the lens and create an annulus of corneal clearance beneath the reverse-curve zone.
- This innovation, together with high-Dk gas-permeable (GP) materials, helped make overnight orthokeratology feasible by improving lens centration and reducing hypoxic stress.
- When fitting and wear are appropriate, refractive changes generally stabilize after approximately 7–10 nights;
- results vary between patients and may regress during the day.
- Safe use still depends on appropriate fitting, hygiene, patient selection, and follow-up.
Modern Era & Regulatory Milestones
- The U.S. Food and Drug Administration (FDA) approved overnight orthokeratology in 2002 (Paragon CRT®).
- Subsequent regulatory clearance occurred for specific overnight orthokeratology devices; the broader claim that multiple lens designs received clearance across the USA, European Union, and Asia-Pacific requires device-specific regulatory documentation.
- Recognition of orthokeratology’s potential role in myopia control increased during the 2010s, reflected by randomized clinical-trial evidence in 2012 and subsequent meta-analytic evaluation in 2015. These studies documented an expanding clinical evidence base but, by themselves, do not establish the extent of research investment or a transition to mainstream clinical use.
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Keep reading Orthokeratology
11 more sections are included with the Clinical plan.
- Anatomy & Corneal Physiology
- Mechanism of Action
- Lens Design & Parameters
- Patient Selection & Candidacy
- Clinical Fitting & Follow-up Protocol
- Efficacy & Refractive Outcomes