A new paper comparing axial elongation differences among untreated myopes, myopes fitted with a control contact lens and emmetropes has helped further the understanding of myopia control efficacy in the context of normal childhood eye growth.
The study titled ‘Axial length targets for myopia control’ has been accepted for publication in Ophthalmic & Physiological Optics, the peer-reviewed journal of The College of Optometrists (UK) and is now available online via Open Access.
Because young eyes grow, even when not myopic, the paper compares axial elongation among children who remain emmetropic, children with untreated myopia progression, and myopic children managed with CooperVision MiSight 1 day contact lenses.
The comparison uses data from the three-year MiSight 1 day clinical study, the Orinda Longitudinal Study of Myopia (OLSM) and the Singapore Cohort Study of the Risk Factors for Myopia (SCORM).
The analysis revealed the predicted three-year axial elongation for emmetropic children (0.24 mm) is similar to the mean three-year elongation in MiSight 1 day-treated children with myopia (0.30 mm).
In contrast, the axial elongation (0.63 mm) observed in the control group in the MiSight 1 day clinical study was much higher, and similar to virtual cohorts based on the OLSM (0.70 mm) and SCORM (0.65 mm) models for myopia development.
According to the study, this observation suggests that while abnormal myopic eye growth may be managed with MiSight 1 day in age-appropriate children, normal, physiological eye growth may continue as the child ages. It supports the hypothesis that myopic axial elongation “may be superimposed on underlying physiological axial elongation”.
The authors speculated that optically based myopia control treatments may minimise the myopic axial elongation, but retain the underlying physiological elongation observed in emmetropic eyes.
“Some eye growth as part of the aging process is normal – myopic axial elongation is not,” Mr Paul Chamberlain, the paper’s lead author and director of research programs for CooperVision, said.
“Our work further validates that evidence-based interventions can be highly effective in slowing that myopic eye growth.”
According to CooperVision, MiSight 1 day contact lenses have been shown to reduce the rate of axial elongation in children (aged 8-12 at the initiation of treatment) by 52% on average over a three-year period. As measured by spherical refraction, the lens reduced the rate of myopia progression in age-appropriate children by 59% on average over the same period.
“In assessing treatment effectiveness, we caution our industry away from applying arbitrary correction factors to account for normal, physiological eye growth until this has been better understood. Efficacy percentages may seem higher presented in that light, but it complicates understanding and valid comparisons,” co-author Professor Mark Bullimore said.
“Eyecare professionals must be able to rely on the ever-growing body of myopia literature to make evidence-based clinical decisions.”