MyopiaNCT03191942
Variation of Orthokeratology Lens Treatment Zone (VOLTZ) Study
A study testing Modified ortho-k lenses and Ortho-k lenses in people with Myopia, run by The Hong Kong Polytechnic University at 2 sites in Hong Kong.
Trial summary
This project aims to study the effects of treatment characteristics on myopia control in orthokeratology by investigating the effects of modified treatment zone by reducing the lens back optic zone diameter on the effect of myopia control. Read more about this study
- Who is it for?
- Ages 6 to 11 yearsHealthy volunteers can take part
- Conditions the study is for
- Myopia
- What is being tested?
- Modified ortho-k lenses and Ortho-k lenses
- Type of treatment
- Medical device
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 70 participants
- Where
- 2 sitesHong Kong
- Study dates
- 20 Jun 2017to 27 Jul 2021
- Phase
- Interventional
- Are there results?
- None posted in the registry
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 6 to 11 years
- All sexes
- Healthy volunteers accepted
- Child
Who may be able to join
- Manifest myopia between 1.00-4.00D in both eyes at screening visit
- Manifest astigmatism ≤2.50D; with-the-rule astigmatism (axes 180 ± 30)
- 2.50D; astigmatism with other axes ≤0.50D in both eyes at screening visit
- <1.00D difference in manifest spherical equivalent (SE) between the two eyes at screening visit
- Baseline cycloplegic objective refraction between 1.00-4.00D in sphere; astigmatism ≤2.50D; <1.00D difference in manifest SE between the two eyes
- Best-corrected logMAR visual acuity 0.10 or better in both eyes Symmetrical corneal topography with corneal toricity <2.00D in either eye
- Normal ocular health other than myopia
- Agree to be randomized and to attend the scheduled visits and aftercare
Who cannot join
- Contraindications to atropine: known allergies or cardiovascular disease, epilepsy
- Contraindications to contact lens wear and ortho-k: corneal scar, history of ocular inflammation/infection, limbus-to-limbus corneal cylinder and dislocated corneal apex
- Strabismus or amblyopia
- History of myopia control treatment (e.g. soft contact lenses, progressive add spectacles, atropine eye drops)
- Rigid contact lens (including ortho-k) wear experience
- Systemic condition which might affect refractive development (for example, Down syndrome, Marfan's syndrome)
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- Ocular conditions which might affect refractive error (for example, cataract, ptosis)
- Poor response to lens wear including poor lens handling, poor vision and/ocular response after lens modifications
- Poor compliance with schedule visits
Trial locations and contacts
2 sites in 1 country.
Hong Kong2 sites
School of Optometry, The Hong Kong Polytechnic University
Kowloon
School of Optometry
Kowloon
About this study
This project aims to study the effects of treatment characteristics on myopia control in orthokeratology by investigating the effects of modified treatment zone by reducing the lens back optic zone diameter on the effect of myopia control. The project will be a two-year randomized, double-masked (examiner - mask axial length only) study conducted at The Hong Kong Polytechnic University recruiting sixty Chinese subjects aged between 6-11. Subjects will be randomly assigned to two ortho-k groups. The Control group will wear KATT BeFree lens with a BOZD of 6mm while the Test group will wear KATT MC lens with a modified BOZD of 5mm.
Read the detailed description
Orthokeratology (Ortho-k) treatment reduces the degree of myopia of the eye by flattening the central cornea. This central flattened zone is referred to as the treatment zone (TZ). Munnerlyn's formula describes the negative correlation between refractive correction and treatment zone size given a maximum ablation depth limited by the patient's corneal thickness in refractive surgery. This implies smaller TZ for higher myopic reduction and, indeed, a study found marginally smaller TZ of 0.3mm in higher myopic group. In ortho-k, it has been speculated that TZ may be associated with the effect of the treatment. The TZ is defined as the central flattened area enclosed by points with zero power/curvature changes comparing to pre-treatment condition on various topography maps.
Previous studies determine the TZ characteristics based on different types of topographical subtractive maps including tangential, axial and refractive maps. A study compared TZ parameters derived from the three different maps. The study defined the TZ as the area enclosed by zero power change in different subtractive maps; 12 such points equally spaced 30 degree apart to construct a best-fit ellipse. Geometrical center of this ellipse was used to determine the TZ decentration and TZ diameter along vertical and horizontal axes. The study found significantly less TZ decentration and diameter in tangential map comparing to axial and refractive maps and no significant difference between the latter two. Based on these findings, the investigators suggested that either refractive or axial map would be of high validity and accuracy in determining TZ characteristics.
The current study would investigate the effect of TZ on myopic control in ortho-k. TZ, defined as the area enclosed by zero power change in subjective maps will be employed. The tangential and refractive subtractive maps will be used to determine the TZ. Characteristics of the TZ, including diameter, slope, depth, volume, would be analyzed based on topographical subtractive maps and the effect of each of these characteristics on myopia control will be evaluated. The role of pupil size during normal viewing condition (distance and near) will also be investigated.
- Conditions
- Myopia
- Being tested
- Modified ortho-k lenses, Ortho-k lenses
- Keywords
- Myopia control, Orthokeratology, Children, Treatment zone
- Medical subject headings
- Myopia
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Modified ortho-k lensesDevice
KETT MC lens
Ortho-k lensesDevice
KATT BeFree lens
| Study group | Role | What they receive |
|---|---|---|
| Modified ortho-k lenses | Experimental | Participants wearing ortho-k lens with a modified BOZD of 5mm Receives: Device: Modified ortho-k lenses |
| Ortho-k lenses | Active comparator | Participants wearing ortho-k lens with a standardized BOZD of 6mm Receives: Device: Ortho-k lenses |
What is being measured
The primary outcome is the main question the study is designed to answer.
Change in axial length before and after two years of lens wear
To determine the change in axial length measured at baseline and two years after lens wear using IOLMaster
Measured: 2 years
Secondary outcomes (3)
Treatment zone characteristics
Corneal topography will be determined by Medmont topographer and the treatment zone characteristics will be determined from the subtractive maps
Measured: 2 years
Pupil sizes
Photopic and mesotopic pupil sizes
Measured: 2 years
Choroidal thickness
Choroidal thickness measurement will be determined by both LenStar and posterior OCT
Measured: 2 years
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted19 Jun 2017
- Study start20 Jun 2017
- Primary completion21 Mar 2021
- Study completion27 Jul 2021
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Publications (7)Papers the sponsor has linked to this study.
- Other trials for MyopiaStudies of the same condition, open and under way.
- More trials run by The Hong Kong Polytechnic UniversityThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase N/A
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Double blind
- Who is masked
- Participant, Outcomes assessor
- Enrolment
- 70 participants (actual)
Sponsor and investigators
- Lead sponsor
- The Hong Kong Polytechnic University
- Sponsor type
- University, hospital or other
- Responsible party
- Principal investigator, Pauline Cho, The Hong Kong Polytechnic University
- Investigators
- Pauline Cho, phd, Principal investigator, The Hong Kong Polytechnic University
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT03191942
- Sponsor's protocol ID
- HSEARS20170118004
- Status last verified
- Jul 2022
- First submitted
- 14 Jun 2017
- Last updated
- 20 Jul 2022
- Results posted
- No
- Data monitoring committee
- Yes
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- Undecided
Publications
Owens H, Garner LF, Craig JP, Gamble G. Posterior corneal changes with orthokeratology. Optom Vis Sci. 2004 Jun;81(6):421-6. doi: 10.1097/01.opx.0000135097.99877.5d.
PubMed 15201715Lu F, Simpson T, Sorbara L, Fonn D. The relationship between the treatment zone diameter and visual, optical and subjective performance in Corneal Refractive Therapy lens wearers. Ophthalmic Physiol Opt. 2007 Nov;27(6):568-78. doi: 10.1111/j.1475-1313.2007.00520.x.
PubMed 17956362Gifford P, Swarbrick HA. The effect of treatment zone diameter in hyperopic orthokeratology. Ophthalmic Physiol Opt. 2009 Nov;29(6):584-92. doi: 10.1111/j.1475-1313.2009.00672.x. Epub 2009 Aug 3.
PubMed 19663928Tahhan N, Du Toit R, Papas E, Chung H, La Hood D, Holden AB. Comparison of reverse-geometry lens designs for overnight orthokeratology. Optom Vis Sci. 2003 Dec;80(12):796-804. doi: 10.1097/00006324-200312000-00009.
PubMed 14688542Sridharan R, Swarbrick H. Corneal response to short-term orthokeratology lens wear. Optom Vis Sci. 2003 Mar;80(3):200-6. doi: 10.1097/00006324-200303000-00009.
PubMed 12637831Munnerlyn CR, Koons SJ, Marshall J. Photorefractive keratectomy: a technique for laser refractive surgery. J Cataract Refract Surg. 1988 Jan;14(1):46-52. doi: 10.1016/s0886-3350(88)80063-4.
PubMed 3339547Guo B, Cho P, Cheung SW, Kojima R, Vincent S. Optical changes and association with axial elongation in children wearing orthokeratology lenses of different back optic zone diameter. Eye Vis (Lond). 2023 Jul 1;10(1):25. doi: 10.1186/s40662-023-00344-3.
PubMed 37391828
Study at a glance
From the registry record, last updated by the sponsor on 20 Jul 2022. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Variation of Orthokeratology Lens Treatment Zone (VOLTZ) Study
- ClinicalTrials.gov ID
- NCT03191942
- Acronym / sponsor ID
- HSEARS20170118004
- Conditions
- Myopia
- Keywords
- Myopia control, Orthokeratology, Children, Treatment zone
- Study type
- Interventional
- Recruitment status
- Completed
- Enrolment
- 70 participants (actual)
- Lead sponsor
- The Hong Kong Polytechnic UniversityUniversity, hospital or other
- Study start
- 20 Jun 2017 (actual)
- Primary completion
- 21 Mar 2021 (actual)
- Study completion
- 27 Jul 2021 (actual)
- First posted
- 19 Jun 2017 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
This project aims to study the effects of treatment characteristics on myopia control in orthokeratology by investigating the effects of modified treatment zone by reducing the lens back optic zone diameter on the effect of myopia control. The project will be a two-year randomized, double-masked (examiner - mask axial length only) study conducted at The Hong Kong Polytechnic University recruiting sixty Chinese subjects aged between 6-11. Subjects will be randomly assigned to two ortho-k groups. The Control group will wear KATT BeFree lens with a BOZD of 6mm while the Test group will wear KATT MC lens with a modified BOZD of 5mm.
Detailed description
Orthokeratology (Ortho-k) treatment reduces the degree of myopia of the eye by flattening the central cornea. This central flattened zone is referred to as the treatment zone (TZ). Munnerlyn's formula describes the negative correlation between refractive correction and treatment zone size given a maximum ablation depth limited by the patient's corneal thickness in refractive surgery. This implies smaller TZ for higher myopic reduction and, indeed, a study found marginally smaller TZ of 0.3mm in higher myopic group. In ortho-k, it has been speculated that TZ may be associated with the effect of the treatment. The TZ is defined as the central flattened area enclosed by points with zero power/curvature changes comparing to pre-treatment condition on various topography maps.
Previous studies determine the TZ characteristics based on different types of topographical subtractive maps including tangential, axial and refractive maps. A study compared TZ parameters derived from the three different maps. The study defined the TZ as the area enclosed by zero power change in different subtractive maps; 12 such points equally spaced 30 degree apart to construct a best-fit ellipse. Geometrical center of this ellipse was used to determine the TZ decentration and TZ diameter along vertical and horizontal axes. The study found significantly less TZ decentration and diameter in tangential map comparing to axial and refractive maps and no significant difference between the latter two. Based on these findings, the investigators suggested that either refractive or axial map would be of high validity and accuracy in determining TZ characteristics.
The current study would investigate the effect of TZ on myopic control in ortho-k. TZ, defined as the area enclosed by zero power change in subjective maps will be employed. The tangential and refractive subtractive maps will be used to determine the TZ. Characteristics of the TZ, including diameter, slope, depth, volume, would be analyzed based on topographical subtractive maps and the effect of each of these characteristics on myopia control will be evaluated. The role of pupil size during normal viewing condition (distance and near) will also be investigated.
Study design
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Double blind (participant, outcomes assessor)
- Number of arms
- 2
| Arm | Type | Receives |
|---|---|---|
| Modified ortho-k lenses | Experimental | Device: Modified ortho-k lensesParticipants wearing ortho-k lens with a modified BOZD of 5mm |
| Ortho-k lenses | Active comparator | Device: Ortho-k lensesParticipants wearing ortho-k lens with a standardized BOZD of 6mm |
Who may qualify
- Ages
- 6 to 11 years
- Sex
- All
- Healthy volunteers
- Accepted
- Age groups
- Child
Key inclusion criteria (8 listed)
- Manifest myopia between 1.00-4.00D in both eyes at screening visit
- Manifest astigmatism ≤2.50D; with-the-rule astigmatism (axes 180 ± 30)
- <1.00D difference in manifest spherical equivalent (SE) between the two eyes at screening visit
- Baseline cycloplegic objective refraction between 1.00-4.00D in sphere; astigmatism ≤2.50D; <1.00D difference in manifest SE between the two eyes
- Best-corrected logMAR visual acuity 0.10 or better in both eyes Symmetrical corneal topography with corneal toricity <2.00D in either eye
Key exclusion criteria (9 listed)
- Contraindications to atropine: known allergies or cardiovascular disease, epilepsy
- Contraindications to contact lens wear and ortho-k: corneal scar, history of ocular inflammation/infection, limbus-to-limbus corneal cylinder and dislocated corneal apex
- Strabismus or amblyopia
- History of myopia control treatment (e.g. soft contact lenses, progressive add spectacles, atropine eye drops)
- Rigid contact lens (including ortho-k) wear experience
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Modified ortho-k lensesKETT MC lens | Device | Modified ortho-k lenses |
| Ortho-k lensesKATT BeFree lens | Device | Ortho-k lenses |
Primary outcome
Change in axial length before and after two years of lens wear
Time frame: 2 years
To determine the change in axial length measured at baseline and two years after lens wear using IOLMaster
3 secondary outcomes
Treatment zone characteristics
Time frame: 2 years
Pupil sizes
Time frame: 2 years
Choroidal thickness
Time frame: 2 years
Results and safety
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 20 Jul 2022.
- Background: PubMed 15201715Owens H, Garner LF, Craig JP, Gamble G. Posterior corneal changes with orthokeratology. Optom Vis Sci. 2004 Jun;81(6):421-6. doi: 10.1097/01.opx.0000135097.99877.5d.
- Background: PubMed 17956362Lu F, Simpson T, Sorbara L, Fonn D. The relationship between the treatment zone diameter and visual, optical and subjective performance in Corneal Refractive Therapy lens wearers. Ophthalmic Physiol Opt. 2007 Nov;27(6):568-78. doi: 10.1111/j.1475-1313.2007.00520.x.
- Background: PubMed 19663928Gifford P, Swarbrick HA. The effect of treatment zone diameter in hyperopic orthokeratology. Ophthalmic Physiol Opt. 2009 Nov;29(6):584-92. doi: 10.1111/j.1475-1313.2009.00672.x. Epub 2009 Aug 3.
- Background: PubMed 14688542Tahhan N, Du Toit R, Papas E, Chung H, La Hood D, Holden AB. Comparison of reverse-geometry lens designs for overnight orthokeratology. Optom Vis Sci. 2003 Dec;80(12):796-804. doi: 10.1097/00006324-200312000-00009.
- Background: PubMed 12637831Sridharan R, Swarbrick H. Corneal response to short-term orthokeratology lens wear. Optom Vis Sci. 2003 Mar;80(3):200-6. doi: 10.1097/00006324-200303000-00009.
- Background: PubMed 3339547Munnerlyn CR, Koons SJ, Marshall J. Photorefractive keratectomy: a technique for laser refractive surgery. J Cataract Refract Surg. 1988 Jan;14(1):46-52. doi: 10.1016/s0886-3350(88)80063-4.
- Derived from this study: PubMed 37391828Guo B, Cho P, Cheung SW, Kojima R, Vincent S. Optical changes and association with axial elongation in children wearing orthokeratology lenses of different back optic zone diameter. Eye Vis (Lond). 2023 Jul 1;10(1):25. doi: 10.1186/s40662-023-00344-3.
- Individual participant dataSharing planned: Undecided
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
Pauline Cho, phd principal investigator
The Hong Kong Polytechnic University
2 sites in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A study testing Modified ortho-k lenses and Ortho-k lenses in people with Myopia, run by The Hong Kong Polytechnic University at 2 sites in Hong Kong.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 8 inclusion and 9 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: finished, as of the sponsor's last update on 20 Jul 2022. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 2 sites in Hong Kong. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Change in axial length before and after two years of lens wear (time frame: 2 years). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
On the ClinicalTrials.gov record for NCT03191942, which also lists 7 linked publications.
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 20 Jul 2022.