Myopic Progression
Conditions
Keywords
myopia control, orthokeratology
Brief summary
Orthokeratology (ortho-k) is a clinical technique that uses reverse geometry rigid gas permeable contact lens exerting positive pressure on the central cornea to temporary reduce refractive error. Researchers have shown that this treatment is effective for myopia control in low to high myopes, with and without astigmatism. Most designs of ortho-k lenses in the market are fitted based on the Jessen formula. The compression factor was introduced to compensate for the regression of the ortho-k effect during the no lens-wear period, so that the wearer can obtain clear distance vision throughout the day and most lens designs use a compression factor of 0.50-0.75 D. However, in a retrospective study (mixed brands of ortho-k lenses), it showed that most patients did not achieve an over-correction of 0.75 D. In order to achieve an over-correction of 0.75 D, an extra flattening power of about 1.50 D instead of 0.75 D should be be targeted. The increased compression factor is expected to increase the target reduction and it may play a role in myopic control and providing a higher successful rate in fitting ortho-k lenses.
Detailed description
Subjects were fitted with ortho-k lenses of conventional (0.75 D) and increased (1.75 D) compression factor. The laterality of the compression factor for each subject was randomised. Subjects were instructed and trained with proper lens handling and disinfection procedures. Lenses were given to the subjects only when they demonstrated proper techniques. All subjects were required to attend regular follow-ups (baseline, first overnight, and weekly over one-month period). The follow-ups were scheduled (except for the first overnight which was scheduled in the early morning) at a similar time to the baseline visit (+/- 2 hours) to minimise any potential influence of diurnal variation on ocular biometrics. Additional unscheduled visits were provided when necessary to ensure good ocular health and vision throughout the study period.
Interventions
DEVICEOrthokeratology
It is a kind of rigid permeable lens.
Sponsors
Menicon Co., Ltd.
Queensland University of Technology
Aston University
The Hong Kong Polytechnic University
Study design
Allocation
RANDOMIZED
Intervention model
SINGLE_GROUP
Primary purpose
TREATMENT
Masking
DOUBLE (Subject, Outcomes Assessor)
Eligibility
Sex/Gender
ALL
Age
6 Years to 10 Years
Healthy volunteers
Yes
Inclusion criteria
1. 6 to 10 years old 2. Myopia: between 0.50 D and 4.00 D in both eyes 3. Astigmatism: \<1.50 D; ≤ 1.25 D for with-the-rule astigmatism (axes 180 ± 30); ≤ 0.50 D for astigmatism of other axes in both eyes 4. Anisometropia: ≤ 1.50 D 5. Symmetrical corneal topography with corneal toricity \<2.00 D in both eyes 6. Agree for randomization
Exclusion criteria
1. Contraindications for orthokeratology wear (e.g. limbus-to-limbus corneal cylinder and dislocated corneal apex) 2. Any type of strabismus or amblyopia 3. Myopic treatment (e.g. refractive surgery and progressive lens wear for myopic control) before and during the study period 4. Rigid contact lenses (including orthokeratology lenses) experience 5. Systemic condition which might affect refractive development (for example, Down syndrome, Marfan's syndrome) 6. Ocular conditions which might affect the refractive error (for example, cataract, ptosis) 7. Poor compliance for lens wear or follow-up
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Changes in Spherical Equivalent Refraction | baseline and one month | Maximum plus for maximum visual acuity was used as the criterion for subjective refraction. Spherical equivalent refraction was calculated by adding the sum of the sphere power with half of the cylinder power. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Changes in Subfoveal Choroidal Thickness | baseline and one month | The subfoveal choroidal thickness was determined as the thickness between the outer retinal pigment epithelium/Bruch's membrane complex and the inner chorioscleral interface. |
| Changes in Higher Order Aberrations | baseline and one month | Ocular higher order aberrations were measured using Shack-Hartmann aberrometer. The wavefront data was fitted with a sixth order Zernike polynomial over a 5-mm pupil size. |
Countries
China
Participant flow
Pre-assignment details
All subjects who passed the inclusion and exclusion criteria at the baseline visit would be assigned to the treatment for each eye according to the randomization log.
Participants by arm
| Arm | Count |
|---|---|
| Orthokeratology Lenses With Different Compression Factors Orthokeratology lenses with different compression factors (one eye with 0.75 D and the fellow eye with 1.75 D) were randomly assigned to each subject. | 28 |
| Orthokeratology Lenses With Different Compression Factors Orthokeratology lenses with different compression factors (one eye with 0.75 D and the fellow eye with 1.75 D) were randomly assigned to each subject. | 56 |
| Total | 84 |
Baseline characteristics
| Characteristic | Orthokeratology Lenses With Different Compression Factors |
|---|---|
| Age, Continuous | 9.3 years |
| Sex: Female, Male Female | 16 Participants |
| Sex: Female, Male Male | 12 Participants |
| Spherical equivalent refraction Conventional compression factor (0.75 D) | 2.12 D STANDARD_DEVIATION 0.94 |
| Spherical equivalent refraction Increased compression factor (1.75 D) | 2.09 D STANDARD_DEVIATION 0.97 |
Adverse events
| Event type | EG000 affected / at risk | EG001 affected / at risk |
|---|---|---|
| deaths Total, all-cause mortality | 0 / 28 | 0 / 28 |
| other Total, other adverse events | 0 / 28 | 0 / 28 |
| serious Total, serious adverse events | 0 / 28 | 0 / 28 |
Outcome results
Primary
Changes in Spherical Equivalent Refraction
Maximum plus for maximum visual acuity was used as the criterion for subjective refraction. Spherical equivalent refraction was calculated by adding the sum of the sphere power with half of the cylinder power.
Time frame: baseline and one month
Population: Orthokeratology lenses with different compression factors (one eye with 0.75 D and the fellow eye with 1.75 D) were randomly assigned to each subject.
| Arm | Measure | Group | Value (MEAN) | Dispersion |
|---|---|---|---|---|
| Orthokeratology Lenses With Different Compression Factors | Changes in Spherical Equivalent Refraction | Conventional compression factor (0.75 D) | 2.31 D | Standard Deviation 0.88 |
| Orthokeratology Lenses With Different Compression Factors | Changes in Spherical Equivalent Refraction | Increased compression factor (1.75 D) | 2.52 D | Standard Deviation 0.85 |
Secondary
Changes in Higher Order Aberrations
Ocular higher order aberrations were measured using Shack-Hartmann aberrometer. The wavefront data was fitted with a sixth order Zernike polynomial over a 5-mm pupil size.
Time frame: baseline and one month
Population: Orthokeratology lenses with different compression factors (one eye with 0.75 D and the fellow eye with 1.75 D) were randomly assigned to each subject.
| Arm | Measure | Group | Value (MEAN) | Dispersion |
|---|---|---|---|---|
| Orthokeratology Lenses With Different Compression Factors | Changes in Higher Order Aberrations | Increased compression factor (1.75 D) | 0.1870 um | Standard Error 0.03 |
| Orthokeratology Lenses With Different Compression Factors | Changes in Higher Order Aberrations | Conventional compression factor (0.75 D) | 0.2830 um | Standard Error 0.03 |
Secondary
Changes in Subfoveal Choroidal Thickness
The subfoveal choroidal thickness was determined as the thickness between the outer retinal pigment epithelium/Bruch's membrane complex and the inner chorioscleral interface.
Time frame: baseline and one month
Population: Orthokeratology lenses with different compression factors (one eye with 0.75 D and the fellow eye with 1.75 D) were randomly assigned to each subject.
| Arm | Measure | Group | Value (MEAN) | Dispersion |
|---|---|---|---|---|
| Orthokeratology Lenses With Different Compression Factors | Changes in Subfoveal Choroidal Thickness | Conventional compression factor (0.75 D) | -1 um | Standard Deviation 30 |
| Orthokeratology Lenses With Different Compression Factors | Changes in Subfoveal Choroidal Thickness | Increased compression factor (1.75 D) | -6 um | Standard Deviation 30 |