Toric Orthokeratology - Slowing Eye Elongation (TO-SEE)

Toric Orthokeratology for Slowing Eye Elongation in Astigmatic Children

The aims of this study are to investigate the effects of ortho-k for astigmatic and myopic reduction and myopic control in children, and the long term effects on corneal curvatures and biomechanics.

Study Overview

• Status: Completed
• Conditions: Astigmatism; Myopia
• Intervention / Treatment: Device: Toric Orthokeratology lenses; Device: Single-vision spectacles

Detailed Description

Ortho-k has been shown to be effective in correcting low myopia but relatively ineffective for astigmatism, using spherical reverse geometry lens designs. Toric ortho-k lenses have been introduced in recent years but the efficacy for astigmatic reduction and for myopic control in children have not been confirmed. The mechanism of myopic reduction in ortho-k cannot be fully explained by changes to the anterior corneal curvatures. It is therefore possible that other corneal parameters such as posterior corneal curvature and corneal biomechanics may contribute to the mechanism.

The current study aims at investigating the efficacy of toric ortho-k lenses for correcting myopic astigmatism and for retarding myopic progression in children compared to children wearing single-vision spectacles. Long term changes to other corneal parameters such as posterior cornea curvatures, topographical corneal thickness, corneal hysteresis, corneal resistance factor, with and without ortho-k lens wear will also be investigated.

• Study Type: Interventional
• Enrollment (Actual): 80
• Phase: Not Applicable

Contacts and Locations

Study Locations

• China
  • Hong Kong SAR, China
    • School of Optometry, The Hong Kong Polytechnic University

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 6 years to 12 years (CHILD)
• Accepts Healthy Volunteers: Yes
• Genders Eligible for Study: All

Description

Inclusion Criteria:

• Myopia (refractive sphere): more than -0.50DS to -5.00DS
• Astigmatism: with-the-rule astigmatism more than -1.25DC
• Anisometropia: ≤ 1.50D in both refractive sphere
• Best corrected monocular visual acuity: equal to or better than 0.10 in logMAR scale in both eyes
• Availability for follow-up for at least 2 years

Exclusion Criteria:

• Strabismus at distance or near
• Contraindication for contact lens wear and orthokeratology (e.g. limbus to limbus corneal cylinder and dislocated corneal apex
• Prior experience with the use of rigid lenses (including orthokeratology)
• Prior experience with myopia control treatment (e.g. refractive therapy or progressive spectacles)
• Systemic or ocular conditions which may affect contact lens wear (e.g. allergy and medication)
• Systemic or ocular conditions which may affect refractive development (e.g. Down syndrome, ptosis)

Study Plan

How is the study designed?

Design Details

• Primary Purpose: TREATMENT
• Allocation: NON_RANDOMIZED
• Interventional Model: PARALLEL
• Masking: SINGLE

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
EXPERIMENTAL: Toric orthokeratology lenses; Children wearing toric ortho-k lenses at night for correcting astigmatism and myopia will be the study group	Device: Toric Orthokeratology lenses; Children wearing toric orthokeratology at night for correcting astigmatism and myopia will be the study group; Other Names: corneal reshaping therapy
OTHER: Single-vision spectacles; Children wearing single-vision spectacles in the daytime for correcting the refractive error will be serve as control group	Device: Single-vision spectacles; Children wearing single-vision spectacles in the daytime for correcting the refractive errors will serve as the control group; Other Names: glasses

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Time Frame
To determine the eyeball elongation in children wearing ortho-k lenses	Before lens wear, 6, 12,18, 24 months after lens wear

Secondary Outcome Measures

Outcome Measure	Time Frame
To determine the posterior corneal curvatures, topographic corneal thickness, corneal volume, corneal hysteresis and corneal resistance factor in a group of children and compare these parameters with the ortho-k children	Before lens wear, 6, 12,18, 24 months after lens wear
To investigative the efficacy of toric orthokeratology for correcting astigmatism and myopia	Before lens wear, 6, 12,18, 24 months after lens wear

Collaborators and Investigators

• Sponsor: The Hong Kong Polytechnic University
• Collaborators: Menicon Co., Ltd.

Publications and helpful links

General Publications

• 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.
• Chen CC, Cheung SW, Cho P. Toric orthokeratology for highly astigmatic children. Optom Vis Sci. 2012 Jun;89(6):849-55. doi: 10.1097/OPX.0b013e318257c20f.
• Chen C, Cho P. Toric orthokeratology for high myopic and astigmatic subjects for myopic control. Clin Exp Optom. 2012 Jan;95(1):103-8. doi: 10.1111/j.1444-0938.2011.00616.x. Epub 2011 Sep 5. No abstract available.

Study record dates

Study Major Dates

• Study Start: May 1, 2008
• Primary Completion (ACTUAL): July 1, 2012
• Study Completion (ACTUAL): December 1, 2012

Study Registration Dates

• First Submitted: September 16, 2009
• First Submitted That Met QC Criteria: September 16, 2009
• First Posted (ESTIMATE): September 17, 2009

Study Record Updates

• Last Update Posted (ESTIMATE): February 22, 2016
• Last Update Submitted That Met QC Criteria: February 18, 2016
• Last Verified: February 1, 2016

More Information

Terms related to this study

• Keywords: Astigmatism; Myopia; Orthokeratology; Corneal thickness; Corneal biomechanics; Corneal curvatures
• Additional Relevant MeSH Terms: Eye Diseases; Refractive Errors; Astigmatism; Myopia
• Other Study ID Numbers: H-ZG30