Toric Orthokeratology - Slowing Eye Elongation

Study Overview
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Brief Summary
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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
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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.

Official Title
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Toric Orthokeratology for Slowing Eye Elongation in Astigmatic Children

Conditions
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Myopia, Astigmatism

Intervention / Treatment
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* Device: Toric Orthokeratology lenses
* Device: Single-vision spectacles


Participation Criteria
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Eligibility Criteria
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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)

Ages Eligible for Study
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Minimum Age: 6 Years
Maximum Age: 12 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Allocation: Non-Randomized
Intervention Model: Parallel Assignment
Masking: Single


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Toric orthokeratology lenses<br>Children wearing toric ortho-k lenses at night for correcting astigmatism and myopia will be the study group | Device: Toric Orthokeratology lenses<br>* Children wearing toric orthokeratology at night for correcting astigmatism and myopia will be the study group<br>* Other names: corneal reshaping therapy;|
| Other: Single-vision spectacles<br>Children wearing single-vision spectacles in the daytime for correcting the refractive error will be serve as control group | Device: Single-vision spectacles<br>* Children wearing single-vision spectacles in the daytime for correcting the refractive errors will serve as the control group<br>* Other names: glasses;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | 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 Outcome Measures

| Outcome Measure | Measure Description | 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 | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Myopia, Astigmatism, Orthokeratology, Corneal thickness, Corneal curvatures, Corneal biomechanics