Clinical trial NCT00978692: Toric Orthokeratology - Slowing Eye Elongation
Official title: Toric Orthokeratology for Slowing Eye Elongation in Astigmatic Children
Study type: INTERVENTIONAL
Overall status: COMPLETED
Phase: NA
Conditions: Myopia
Astigmatism
Keywords: Myopia
Astigmatism
Orthokeratology
Corneal thickness
Corneal curvatures
Corneal biomechanics
Lead sponsor: The Hong Kong Polytechnic University
Sponsor class: OTHER
Collaborators: name: Menicon Co., Ltd.
First posted: 2009-09-17
Enrollment: 80
Sex: ALL
Minimum age (years): 6
Maximum age (years): 12
Standard ages: CHILD
Accepts healthy volunteers: yes
Allocation: NON_RANDOMIZED
Intervention model: PARALLEL
Primary purpose: TREATMENT

Brief summary: 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.

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.

Eligibility 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)

Primary outcomes:
measure: To determine the eyeball elongation in children wearing ortho-k lenses
timeFrame: Before lens wear, 6, 12,18, 24 months after lens wear
Secondary outcomes:
measure: 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
timeFrame: Before lens wear, 6, 12,18, 24 months after lens wear
measure: To investigative the efficacy of toric orthokeratology for correcting astigmatism and myopia
timeFrame: Before lens wear, 6, 12,18, 24 months after lens wear
Other outcomes:
Locations:
city: Hong Kong SAR
country: China
facility: School of Optometry, The Hong KOng Polytechnic University
Study officials:
affiliation: The Hong Kong Polytechnic University
name: Pauline Cho, PhD
role: PRINCIPAL_INVESTIGATOR
References:
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: 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.
citation: 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.