Toric Orthokeratology - Slowing Eye Elongation

Condition(s) targeted: Myopia; Astigmatism

Intervention: Toric Orthokeratology lenses (Device); Single-vision spectacles (Device)

Phase: N/A

Status: Recruiting

Sponsored by: The Hong Kong Polytechnic University

Official(s) and/or principal investigator(s):
Pauline Cho, PhD, Principal Investigator, Affiliation: The Hong Kong Polytechnic University

Overall contact:
Pauline Cho, PhD, Phone: (+852)2766-6100, Email: sopaulin@inet.polyu.edu.hk

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.

Official title: Toric Orthokeratology for Slowing Eye Elongation in Astigmatic Children

Study design: Treatment, Non-Randomized, Single Blind (Investigator), Parallel Assignment, Safety/Efficacy Study

Primary outcome: To determine the eyeball elongation in children wearing ortho-k lenses

Secondary outcome:

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

To investigative the efficacy of toric orthokeratology for correcting astigmatism and myopia

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.

Minimum age: 6 Years. Maximum age: 12 Years. Gender(s): Both.

Criteria:

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)

Pauline Cho, PhD, Phone: (+852)2766-6100, Email: sopaulin@inet.polyu.edu.hk

School of Optometry, The Hong KOng Polytechnic University, Hong Kong SAR, China; Recruiting
Pauline Cho, PhD, Phone: (+852)2766-6100, Email: sopaulin@inet.polyu.edu.hk
Connie Chen, BSc, Phone: (+852)2766-4467, Email: 07902317r@polyu.edu.hk
Pauline Cho, PhD, Principal Investigator

Starting date: May 2008
Ending date: December 2011
Last updated: September 16, 2009