Multifocal orthokeratology and myopia progression in children

Abstract

Purpose: To test the efficacy of a newly developed multifocal orthokeratology (MOK) lens in slowing myopia progression in children. The MOK lens was worn overnight and moulded a concentric multifocal surface pattern onto the anterior of the corneal epithelium. Thus, the retina was exposed to an image focused on the retina to give clear vision and simultaneously exposed to a second image focused anterior to the retina to create myopic defocus on the retina to slow eye elongation. Methods: Thirty children aged between 10 and 14 years were enrolled in this prospective, randomised, investigator-masked, paired-eye clinical trial. Each participant was fitted with the novel MOK lens in one (pseudo-randomly assigned) eye, while the fellow eye was fitted with a conventional orthokeratology (OK) lens as control. Myopia progression was monitored every 6 months over a period of 18 months with lowcoherence reflectometry in both eyes, obtaining measurements of the change in axial length (AL) of the eye, vitreous chamber depth (VCD), inner axial length (IAL) of the eye and choroid thickness. Changes in relative peripheral refraction were also monitored across the central 70° of each retina. Results: We found an immediate shortening effect in the MOK eyes for AL, VCD and IAL after only 27 days of lens wear. The shortening was sustained over 18 months for AL and VCD. The change between MOK and conventional OK for AL (p = 0.001), VCD (0.002) and IAL (p = 0.022) was significant. Moreover, a significant increase (immediate and long term) in choroid thickness occurred in eyes treated with MOK compared with eyes wearing conventional OK (p = 0.011). In both eyes, peripheral refractions changed significantly from relative hyperopia at baseline to relative myopia after the initial lens fitting (p < 0.001) and remained unchanged afterwards. Conclusion: MOK induced an immediate and sustained shortening of AL and VCD and stabilised IAL growth. Therefore, exposing the retina to simultaneous on-axis myopic defocus appeared to have an additive effect in slowing myopia progression, in addition to the relative myopic peripheral refraction associated with conventional OK. The results of this study indicate that MOK is more effective than conventional OK in controlling myopia progression in children.