Interventions to limit the progression of myopia

Abstract

Myopia is invariably a lifelong condition characterised by high prevalence, significant risk in terms of associated ocular pathology, due to its increased axial length, and a substantial economic and social burden. While myopia can be corrected with spectacles and standard contact lenses, neither protect the eye from continued growth nor increased progression. At birth, the eye’s refractive error can be significant. As the eye grows the magnitudeof refractive error commonly reduces in a process termed ‘emmetropisation’. Substantial evidence exists to suggest that emmetropisation is an active process which relies on a normal visual experience, the absence of which in early life typically results in a refractive error. Research from animal models has shown the peripheral retina also plays a role in the emmetropisation process. Modification of the peripheral focus has been found to influence myopia progression. This thesis is stimulated by the findings of Anstice and Phillips (2011) who, using a Dual-Focus contact lens, which provided clear central vision and simultaneous peripheral myopic retinal defocus, showed a reduction in axial myopic progression in children. This thesis aims to describe the efficacy of a parallel-group, double blind and randomised controlled trial of a dual focus contact lens to slow myopia progression in children. Biometric data were compared for 27 myopic child participants aged 8 to 12 years at baseline. Children who wore the test lens had 41% less progression of myopia as measured by cycloplegic refraction and 44.5% less axial elongation after 12 months of lens wear. Additionally, the effect of lag of accommodation, peripheral refractive error, pupil size and time spent outdoors were explored. This thesis demonstrates that peripheral retinal defocus plays a role in slowing the progression of myopia in children and that interventions to limit the progression of myopia may need to be tailored to individual characteristics.