George Jessen, a US optometrist, was first to propose that the corneal shape could be deliberately altered to reduce myopia by fitting hard lenses with a back optic zone radius (BOZR) significantly flatter than the corneal radius (Jessen 1962). This approach, which Jessen named the orthofocus technique, was controversial at the time but its basic principles laid the foundation for modern orthokeratology (also known as ortho-k). Orthokeratology has been defined as ‘the reduction, modification or elimination of a visual defect by the programmed application of contact lenses’ (Kerns 1976a) and represents a more active approach to myopia correction. The ultimate aim of orthokeratology is to eliminate refractive error or to reduce it to a sufficiently small degree that the patient can function without spectacles or contact lenses for most of the waking day (Cheung et al. 2007; Mountford et al. 2004). When the desired result has been achieved, the new corneal shape is maintained using retainer lenses (Gasson and Morris 2003; Mountford et al. 2004). In the context of optometric practice, orthokeratology applies only to the correction of mild to moderate myopia; however, it has also been shown to be effective in the correction of hyperopia and presbyopia in a research context (Gifford and Swarbrick 2013; Gifford et al. 2009). Orthokeratology is a convenient method of refractive error correction because the lenses are worn part-time (generally overnight), allowing the patient freedom from spectacles and contact lenses during waking hours.