The primary objective of the current study is to investigate changes in peripheral refraction and aberration in children wearing orthokeratology lenses and single-vision spectacles.

Apart from being effective in reducing low to moderate myopia, orthokeratology has been shown to have potential in retarding myopic progression. The central cornea is flattened and peripheral optics altered in orthokeratology and it has been suggested that orthokeratology slows myopic progression through the alteration of peripheral optics. The aim of the current study is to investigate the changes in peripheral refraction and aberration in children wearing orthokeratology (study group) and single-vision spectacles (control group).

Inclusion Criteria:

• Myopia (refractive sphere): > 0.50D and ≤ 6.00D
• Astigmatism: with-the-rule astigmatism (axes 180 +/- 30) ≤ 1.50D; astigmatism of other axes ≤ 0.50D
• Spherical equivalent (SE): > 0.50D and ≤ 6.75D (myopia)
• Best corrected monocular visual acuity: equal to or better than 6/7.5 in Snellen scale
• Willingness to wear contact lenses or spectacles on a daily basis
• Availability for follow-up for at least 2 years

Exclusion Criteria:

• Strabismus at distance or near
• Contraindication for contact lens wear and orthokeratology (e.g. limbus to limbus corneal cylinder and dislocated corneal apex)
• Prior experience with the use of rigid lenses (including orthokeratology)
• Prior experience with myopic control treatment (e.g. refractive therapy or progressive spectacles)
• Systemic or ocular conditions which may affect contact lens wear (e.g. allergy and medication)
• Systemic or ocular conditions which may affect refractive development (e.g. Down syndrome, ptosis)