Clinical trial NCT02643875: Investigation of the Effect of Short-term Orthokeratology With Increased Compression Factor on Ocular Parameters
Official title: Investigation of the Effect of Short-term Orthokeratology With Increased Compression Factor on Ocular Parameters
Study type: INTERVENTIONAL
Overall status: COMPLETED
Phase: NA
Conditions: Myopic Progression
Keywords: myopia control
orthokeratology
Lead sponsor: The Hong Kong Polytechnic University
Sponsor class: OTHER
Collaborators: name: Menicon Co., Ltd.
name: Queensland University of Technology
name: Aston University
First posted: 2015-12-31
Enrollment: 36
Sex: ALL
Minimum age (years): 6
Maximum age (years): 10
Standard ages: CHILD
Accepts healthy volunteers: yes
Allocation: RANDOMIZED
Intervention model: SINGLE_GROUP
Primary purpose: TREATMENT

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.

Eligibility criteria: 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

Primary outcomes:
measure: Changes in Spherical Equivalent Refraction
timeFrame: baseline and one month
Secondary outcomes:
measure: Changes in Subfoveal Choroidal Thickness
timeFrame: baseline and one month
measure: Changes in Higher Order Aberrations
timeFrame: baseline and one month
Other outcomes:
Locations:
city: Hong Kong
country: China
facility: The Hong Kong Polytechnic University
Study officials:
affiliation: The Hong Kong Polytechnic University
name: Pauline Cho, PhD
role: PRINCIPAL_INVESTIGATOR
References:
citation: Cho P, Cheung SW, Edwards M. The longitudinal orthokeratology research in children (LORIC) in Hong Kong: a pilot study on refractive changes and myopic control. Curr Eye Res. 2005 Jan;30(1):71-80. doi: 10.1080/02713680590907256.
citation: Cho P, Cheung SW. Retardation of myopia in Orthokeratology (ROMIO) study: a 2-year randomized clinical trial. Invest Ophthalmol Vis Sci. 2012 Oct 11;53(11):7077-85. doi: 10.1167/iovs.12-10565.
citation: Chen C, Cheung SW, Cho P. Myopia control using toric orthokeratology (TO-SEE study). Invest Ophthalmol Vis Sci. 2013 Oct 3;54(10):6510-7. doi: 10.1167/iovs.13-12527.
citation: Chan B, Cho P, Mountford J. The validity of the Jessen formula in overnight orthokeratology: a retrospective study. Ophthalmic Physiol Opt. 2008 May;28(3):265-8. doi: 10.1111/j.1475-1313.2008.00545.x.
citation: Wan K, Lau JK, Cheung SW, Cho P. Refractive and corneal responses of young myopic children to short-term orthokeratology treatment with different compression factors. Cont Lens Anterior Eye. 2020 Feb;43(1):65-72. doi: 10.1016/j.clae.2019.10.134. Epub 2019 Nov 6.
citation: Lau JK, Vincent SJ, Cheung SW, Cho P. The influence of orthokeratology compression factor on ocular higher-order aberrations. Clin Exp Optom. 2020 Jan;103(1):123-128. doi: 10.1111/cxo.12933. Epub 2019 Jul 1.
citation: Lau JK, Wan K, Cheung SW, Vincent SJ, Cho P. Weekly Changes in Axial Length and Choroidal Thickness in Children During and Following Orthokeratology Treatment With Different Compression Factors. Transl Vis Sci Technol. 2019 Jul 23;8(4):9. doi: 10.1167/tvst.8.4.9. eCollection 2019 Jul.