Astigmatism, Myopia
Conditions
Keywords
Myopia, Astigmatism, Orthokeratology, Corneal thickness, Corneal curvatures, Corneal biomechanics
Brief summary
The aims of this study are to investigate the effects of ortho-k for astigmatic and myopic reduction and myopic control in children, and the long term effects on corneal curvatures and biomechanics.
Detailed description
Ortho-k has been shown to be effective in correcting low myopia but relatively ineffective for astigmatism, using spherical reverse geometry lens designs. Toric ortho-k lenses have been introduced in recent years but the efficacy for astigmatic reduction and for myopic control in children have not been confirmed. The mechanism of myopic reduction in ortho-k cannot be fully explained by changes to the anterior corneal curvatures. It is therefore possible that other corneal parameters such as posterior corneal curvature and corneal biomechanics may contribute to the mechanism. The current study aims at investigating the efficacy of toric ortho-k lenses for correcting myopic astigmatism and for retarding myopic progression in children compared to children wearing single-vision spectacles. Long term changes to other corneal parameters such as posterior cornea curvatures, topographical corneal thickness, corneal hysteresis, corneal resistance factor, with and without ortho-k lens wear will also be investigated.
Interventions
DEVICEToric Orthokeratology lenses
Children wearing toric orthokeratology at night for correcting astigmatism and myopia will be the study group
DEVICESingle-vision spectacles
Children wearing single-vision spectacles in the daytime for correcting the refractive errors will serve as the control group
Sponsors
Menicon Co., Ltd.
The Hong Kong Polytechnic University
Study design
Allocation
NON_RANDOMIZED
Intervention model
PARALLEL
Primary purpose
TREATMENT
Masking
SINGLE (Investigator)
Eligibility
Sex/Gender
ALL
Age
6 Years to 12 Years
Healthy volunteers
Yes
Inclusion criteria
* Myopia (refractive sphere): more than -0.50DS to -5.00DS * Astigmatism: with-the-rule astigmatism more than -1.25DC * Anisometropia: ≤ 1.50D in both refractive sphere * Best corrected monocular visual acuity: equal to or better than 0.10 in logMAR scale in both eyes * 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 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)
Design outcomes
Primary
| Measure | Time frame |
|---|---|
| To determine the eyeball elongation in children wearing ortho-k lenses | Before lens wear, 6, 12,18, 24 months after lens wear |
Secondary
| Measure | Time frame |
|---|---|
| To determine the posterior corneal curvatures, topographic corneal thickness, corneal volume, corneal hysteresis and corneal resistance factor in a group of children and compare these parameters with the ortho-k children | Before lens wear, 6, 12,18, 24 months after lens wear |
| To investigative the efficacy of toric orthokeratology for correcting astigmatism and myopia | Before lens wear, 6, 12,18, 24 months after lens wear |
Countries
China
Outcome results
None listed