Discontinuation of Orthokeratology on Eyeball Elongation in Myopic 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). Both studies showed that the effect of myopic control was most significant during the first six months of the treatment. It is unknown whether the myopic control effect would dissipate upon the discontinuation of the treatment or whether the myopic control effect only happened in the first six month of lens wear and was maintained thereafter. The current study aims at evaluating the effect of discontinuation of ortho-k treatment on myopic control in children who are currently on the treatment. This knowledge is necessary and important as patients/parents have concerns about the permanent dependency on ortho-k once they enrolled in the treatment.

Children who have been on the treatment for two years and have recently completed the myopic control studies at The Hong Kong Polytechnic University, i.e. the ROMIO, TO-SEE and HM-PRO studies, will be invited to participate in this 14-month study. Ortho-k subjects will be randomly assigned to study group or the ortho-k control group. The study group subjects will be required to stop lens wear for 7 months at the completion of the previous study (Phase I) and resume lens wear for next 7 months (Phase II). The ortho-k control group subjects will be required to continue the current treatment for another 14 months. Control subjects in the existing myopic control studies will be required to continue using the same treatment, i.e. single-vision glasses, for another 14 months. Rate of myopic progression among the 3 groups and at the two study phases will be determined and compared.

Inclusion criteria

• Age 8-14 years old (inclusive)
• Subjects who have completed the ROMIO, TO-SEE or HM-PRO studies at The Hong Kong Polytechnic University
• Willingness to be randomized into groups (for ortho-k subjects)
• Availability for follow-up for at least 14 months

Exclusion criteria

• Non-compliance to the follow up schedule
• Non-compliance to the assigned optical correction (i.e. single-vision glasses or ortho-k lenses)
• 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)