Investigation of the Effect of Short-term Orthokeratology With Increased Compression Factor on Ocular Parameters

Myopic Progression Clinical Trial

Official title:

Investigation of the Effect of Short-term Orthokeratology With Increased Compression Factor on Ocular Parameters

Clinical Trial Details — Status: Completed

Administrative data

• NCT number: NCT02643875
• Other study ID #: HSEARS20151002004
• Status: Completed
• Phase: N/A
• Start date: February 26, 2016
• Est. completion date: November 18, 2016

Study information

• Verified date: February 2020
• Source: The Hong Kong Polytechnic University
• Contact: n/a
• Is FDA regulated: No
• Study type: Interventional

Clinical Trial 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.

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.

Recruitment information / eligibility

• Status: Completed
• Enrollment: 36
• Est. completion date: November 18, 2016
• Est. primary completion date: November 18, 2016
• Accepts healthy volunteers: Accepts Healthy Volunteers
• Gender: All
• Age group: 6 Years to 10 Years

Eligibility

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

Related Conditions & MeSH terms

• Disease Progression
• Myopic Progression

Intervention

Device:
• Orthokeratology
It is a kind of rigid permeable lens.

Locations

Country	Name	City	State
China	The Hong Kong Polytechnic University	Hong Kong

Sponsors (4)

Lead Sponsor	Collaborator
The Hong Kong Polytechnic University	Aston University, Menicon Co., Ltd., Queensland University of Technology

Country where clinical trial is conducted

China, 

References & Publications (7)

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. — View 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. — View 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. — View 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. — View 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. — View 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/tvs — View 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 — View Citation

Outcome

Type	Measure	Description	Time frame	Safety issue
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.	baseline and one month
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.	baseline and one month
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.	baseline and one month