Orthokeratology for High Myopia (OHM) Study

Not Applicable

• Conditions: High Myopia; Myopia
• Interventions: Device: ortho-k lenses and thinner spectacles; Device: newly designed ortho-k lenses

• Registration Number: NCT03881358
• Lead Sponsor: The Hong Kong Polytechnic University

Brief Summary

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

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.

Study Timeline

• Study Start: 2018-08-04
• Study First Submitted: 2019-02-21
• Study First Submitted QC: 2019-03-18
• Study First Posted: 2019-03-19
• Status Verified: 2021-02
• Last Update Submitted: 2021-02-14
• Last Update Posted: 2021-02-16
• Primary Completion: 2023-11
• Study Completion: 2024-01

Recruitment & Eligibility

• Status: UNKNOWN
• Sex: All
• Target Recruitment: 66

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

Study & Design

• Study Type: INTERVENTIONAL
• Study Design: PARALLEL

Arm && Interventions

Group	Intervention	Description
ortho-k lenses and thinner spectacles	ortho-k lenses and thinner spectacles	participants using conventionally designed ortho-k lenses (target for 4.00D) and thinner spectacles during day time
newly designed ortho-k lenses	newly designed ortho-k lenses	participants using newly designed ortho-k lenses for high myopia (target for full correction)

Primary Outcome Measures

Name	Time	Method
Change in axial length elongation over 24 months.	2 years	To determine the change in axial length measured at baseline and two years after lens wear using IOLMaster

Secondary Outcome Measures

Name	Time	Method
First fit success rate of a newly designed ortho-k lens for high myopic children	1 month	The success rate in using the first pair of lenses to achieve target refractive correction will be determined
Quality of life (questionnaire)	3 months	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
Ocular aberration	2 years	Ocular aberration will be measured by Complete Ophthalmic Analysis System (COAS) aberrometer

Trial Locations

Locations (1)

School of Optometry, The Hong Kong Polytechnic University; 🇭🇰 Kowloon, Hong Kong