Retardation of Myopia in Orthokeratology

Not Applicable

Completed

Interventions: Device: single-vision spectacle lenses
Device: orthokeratology lenses

Brief Summary: The primary aim of this study is to evaluate and compare the eyeball elongation in children wearing orthokeratology lenses and single-vision spectacles.

Detailed Description: Prevalence of myopia is high in Asian countries like Hong Kong. Orthokeratology has shown potential in slowing myopic progression but the efficacy is yet to be confirmed by a randomized clinical trial (RCT). The current RCT aims at studying the efficacy of orthokeratology in retardation of myopic progression by comparing the eye growth in terms of axial length elongation in children wearing orthokeratology lenses (study group) and those wearing single-vision spectacles (control group).

Recruitment & Eligibility

Inclusion Criteria

Myopia (refractive sphere): > 0.50D and ≤ 4.00D
Astigmatism: < ½ of myopia; with-the-rule astigmatism (axes 180 +/- 30) ≤1.25D; astigmatism of other axes ≤ 0.50D
Spherical equivalent (SE): > 0.75D and ≤ 4.50D
Anisometropia: ≤ 1.50D in both refractive sphere, refractive cylinder and SE
Best corrected monocular visual acuity: equal to or better than 0.10 in logMAR scale in both eyes
Willingness for randomization
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 myopia control treatment (e.g. refractive therapy or progressive add 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)

Arm && Interventions

Group	Intervention	Description
single-vision spectacle lenses	single-vision spectacle lenses	Children wearing single-vision spectacles in the daytime for correcting the refractive error will serve as control group
orthokeratology lenses	orthokeratology lenses	Children wearing orthokeratology at night for correcting of refractive error will be study group

Primary Outcome Measures

Name	Time	Method
Axial Elongation in the Study and Control Subjects Who Completed the Two Years Study	2 years	Axial elongation was determined by the change in axial length of the eyeball before and after treatment period. Axial length was measured by the IOLMaster (Zeiss Humphrey, Dublin, CA) 30 minutes after cycloplegia. The measurement of the axial length followed the procedures as recommended by the manufacturer.

Secondary Outcome Measures

Name	Time	Method
Determine the Incidence of Adverse Effects in Cornea, the Palpebral, Bulbar and Tarsal Conjunctiva in the Study and the Control Groups	2 years
Determine Changes in Other Ocular Parameters (e.g. Corneal Biomechanics and Aberration) Associated With Orthokeratology Lens Wear	2 years