Orthokeratology for High Myopia (OHM) Study

Study Overview
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Brief Summary
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This project aims to investigate/examine high myopic subjects on full correction ortho-k (using Topaz ortho-k lenses for high myopia) compared to subjects undergoing partial reduction ortho-k and their relationship with myopia and myopic progression.

Detailed Description
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For many years, commercially-available ortho-k lenses aim to reduce low - moderate myopia. Attempts to use these lenses for reduction of high myopia have been shown to give rise to complications such as corneal staining and lens decentration. Thus, practitioners may choose a more conservative way for high myopic children, that is, offering partial reduction ortho-k. Partial reduction ortho-k is target for 4.00-5.00D reduction and the residual refractive errors will be corrected with single vision spectacles to allow good visual acuity in the daytime. Partial reduction ortho-k has been shown to slow axial elongation in high myopic children, however, the main disadvantage is that the children have to wear spectacles in the daytime to correct residual refraction. Euclid has recently designed a new lens, Euclid's Topaz, for high myopic children. It is currently commercially available to correct myopia for up to 10 D. However, evidence of its effectiveness for visual correction and slowing AL growth is lacking. While numerous studies have shown that orthokeratology is an effective clinical treatment to slow axial eye growth in children, the exact mechanism underlying this reduction in myopia progression associated with orthokeratology remains unclear.

Official Title
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Orthokeratology for High Myopia (OHM) Study

Conditions
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Myopia, High Myopia

Intervention / Treatment
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* Device: ortho-k lenses and thinner spectacles
* Device: newly designed ortho-k lenses


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Myopia: at least 5.00D in one eye or in both eyes Astigmatism: ≤1.50D; with-the-rule astigmatism (axes 180 ± 30) ≤1.25D; astigmatism of other axes ≤0.50D in both eyes Anisometropia: not be more than 1.00D in the former and not more than 2.00D in the latter. Best-corrected Monocular Snellen visual acuity 6/7.5 or better Exclusion Criteria: Strabismus at distance or near Previous experience in contact lens wear or myopia control treatment (e.g. refractive therapy or progressive spectacles) Contraindication for contact lens wear and orthokeratology (e.g. limbus to limbus corneal cylinder and dislocated corneal apex) Previous history of ocular surgery, trauma, or chronic ocular disease Concurrent use of medications that may affect tear quality or contact lens wear Systemic or ocular conditions that may affect tear quality or contact lens wear (e.g allergy and concurrent medication) or that may affect refractive development (e.g Down syndrome, ptosis) Poor compliance to tests (e.g poor fixation in noncontact tonometry or intolerance of lens wear) Not willing to comply with the allocated treatment, use and care of lenses and follow-up schedule

Ages Eligible for Study
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Minimum Age: 7 Years
Maximum Age: 13 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: Randomized
Intervention Model: Parallel Assignment
Masking: Single


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Active Comparator: ortho-k lenses and thinner spectacles<br>participants using conventionally designed ortho-k lenses (target for 4.00D) and thinner spectacles during day time | Device: ortho-k lenses and thinner spectacles<br>* Conventinally designed (Emerald) ortho-k lenses (target for -4.00D) and thinner specs during day time<br>|
| Experimental: newly designed ortho-k lenses<br>participants using newly designed ortho-k lenses for high myopia (target for full correction) | Device: newly designed ortho-k lenses<br>* Newly designed (Topaz) ortho-k lenses for high myopia (target for full correction)<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in axial length elongation over 24 months. | To determine the change in axial length measured at baseline and two years after lens wear using IOLMaster | 2 years | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| First fit success rate of a newly designed ortho-k lens for high myopic children | The success rate in using the first pair of lenses to achieve target refractive correction will be determined | 1 month | 
| Quality of life (questionnaire) | Quality of life will be determined by questionnaires (using revised Pediatric Refractive Error Profile (PREP) 1 in traditional Chinese version) before and after ortho-k in the two groups of subjects | 3 months | 
| Ocular aberration | Ocular aberration will be measured by Complete Ophthalmic Analysis System (COAS) aberrometer | 2 years | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Myopia control, Orthokeratology, Children