Toric Orthokeratology - Slowing Eye Elongation (TO-SEE)

The Hong Kong Polytechnic University

Status: Completed

Conditions: Myopia; Astigmatism

Treatments: Device: Toric Orthokeratology lenses; Device: Single-vision spectacles

Study type: Interventional

Funder types: Other; Industry

Identifiers

NCT00978692

H-ZG30

Details and patient eligibility

About

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.

Full 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.

Enrollment: 80 patients

Sex: All

Ages: 6 to 12 years old

Volunteers: Accepts Healthy Volunteers

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)

Trial design

Primary purpose: Treatment

Allocation: Non-Randomized

Interventional model: Parallel Assignment

Masking: Single Blind

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80 participants in 2 patient groups

Toric orthokeratology lenses

Experimental group

Description:

Children wearing toric ortho-k lenses at night for correcting astigmatism and myopia will be the study group

Treatment:

Device: Toric Orthokeratology lenses

Single-vision spectacles

Other group

Description:

Children wearing single-vision spectacles in the daytime for correcting the refractive error will be serve as control group

Treatment:

Device: Single-vision spectacles