Discontinuation of Lens Wear in New Ortho-k Children (DOEE2)

Discontinuation of Orthokeratology on Eyeball Elongation (DOEE) Study. (2) Discontinuation of Lens Wear in New Ortho-k Children

This study aims at investigating the efficacy of myopic control using ortho-k in younger and older children.

Children wearing ortho-k have been shown to have slower rate of myopic progression than those wearing single-vision spectacles (Cho et al. 2005) or soft lenses (Walline et al. 2009). Younger myopic children (aged 6-10 years old) may have the faster increase in myopia than old myopic children (aged 11-15 years old), i.e. the rate of myopic progression may be different in different age groups and in children with different refractive status (Edwards 1999; Fan et al. 2004; Cheng et al. 2007). Although the refractive correction with ortho-k has been well documented, it is unknown whether the efficiency and reversibility of ortho-k for myopic reduction as well as myopic control are similar in children of different age and refractive groups.

In this 14-month study, the eyeball length in 45 younger (6-10 years old) and 45 older (11-15 years old) myopic children before and after ortho-k will be evaluated. Eyeball elongation will be determined for the first 7 months when single-vision glasses will be prescribed (Phase I) and the next 7 months when ortho-k will be prescribed (Phase I). Rate of myopic progression will be determined and compared between the two groups of children in the two phases.

Inclusion Criteria:

• Age: between 6 to 15 years old
• Myopia: between 1.50D and 4.50D in at least one eye
• Spherical equivalent (SE): between -1.00D to -4.50D in both eyes
• Astigmatism: ≤ 3.00D of axes 180 +/- 30 or ≤ 1.00D of other axes; and the amount is less than refractive sphere
• Anisometropia: ≤ 1.50D in both refractive sphere, refractive cylinder and SE
• Best corrected monocular visual acuity: equal to or better than 0.10 in logMAR scale in both eyes
• Willingness to wear contact lenses or spectacles on a daily basis
• Can obtain good ortho-k results with the study lenses
• Availability for follow-up for at least 14 months

Exclusion Criteria:

• Strabismus at distance or near
• Contraindication for contact lens wear and ortho-k (e.g. limbus to limbus corneal cylinder and dislocated corneal apex
• 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)
• Prior experience with the use of rigid lenses (including ortho-k)
• Prior experience with myopia control treatment (e.g. refractive therapy or progressive spectacles)
• Non-compliance to the follow up schedule
• Non-compliance to the use of the prescribed optical correction
• Poor ocular response to ortho-k lens wear
• Significant residual refractive error after ortho-k treatment resulting in poor unaided vision (worse than 0.18 in logMAR scale)