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

August 30, 2020 updated by: Pauline Cho, The Hong Kong Polytechnic University
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.

Study Overview

Status

Completed

Conditions

Intervention / Treatment

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.

Study Type

Interventional

Enrollment (Actual)

36

Phase

  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • China
      • Hong Kong, China
        • The Hong Kong Polytechnic University

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

6 years to 10 years (Child)

Accepts Healthy Volunteers

No

Genders Eligible for Study

All

Description

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

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: Randomized
  • Interventional Model: Single Group Assignment
  • Masking: Double

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Sham Comparator: Ortho-k lens with normal compression factor
The eye wears ortho-k lens with normal compression factor to achieve plano (+/- 0.25D) correction.
Device: Orthokeratology
It is a kind of rigid permeable lens.
Active Comparator: Ortho-k lenses with increased compression factor
The eye wears ortho-k lenses with increased compression factor to achieve 1 diopter (+/- 0.25D) over correction.
Device: Orthokeratology
It is a kind of rigid permeable lens.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Changes in Spherical Equivalent Refraction
Time Frame: 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.
baseline and one month

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Changes in Subfoveal Choroidal Thickness
Time Frame: 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.
baseline and one month
Changes in Higher Order Aberrations
Time Frame: 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.
baseline and one month

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

The Hong Kong Polytechnic University

Collaborators

Aston University
Queensland University of Technology
Menicon Co., Ltd.

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

February 26, 2016

Primary Completion (Actual)

November 18, 2016

Study Completion (Actual)

November 18, 2016

Study Registration Dates

First Submitted

December 28, 2015

First Submitted That Met QC Criteria

December 29, 2015

First Posted (Estimate)

December 31, 2015

Study Record Updates

Last Update Posted (Actual)

September 18, 2020

Last Update Submitted That Met QC Criteria

August 30, 2020

Last Verified

February 1, 2020

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • HSEARS20151002004

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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