Effect of peripheral defocus on axial eye growth and modulation of refractive error in hyperopes

Abstract

Hyperopia is a known risk factor for the development of strabismus and amblyopia. In addition to visual consequences there is a growing body of evidence that uncorrected hyperopia may have a negative impact on educational attainment and visuocognitive and visuomotor skills. Currently, hyperopia receives much less attention from research than myopia even though the impact of moderate to high levels of hyperopia especially in one eye (anisohyperopia) can lead to amblyopia if not corrected fully at a young age. Hyperopia occurs as a consequence of insufficient ocular growth and a failure to emmetropise in childhood with the majority of hyperopic refractive errors resulting from an eye that is too short for its refractive power. In anisohyperopia it is unclear why one eye may remain hyperopic while the fellow eye grows towards an emmetropic state. Studies on animals have suggested that manipulating peripheral defocus through an optical means while simultaneously providing correct axial focus can either discourage or encourage axial eye growth to effectively treat myopia or hyperopia, respectively. Recent research has established that progression of myopia and axial eye growth can be significantly reduced in children and adolescents through the use of bifocal or multifocal contact lenses. These contact lenses while correcting the distance central myopia impose simultaneous myopic defocus. In recent years there has been a great deal of interest in delaying progression of myopia (short-sightedness) by slowing eye growth using a particular type of contact lens termed a centre-distance multifocal design. There have been encouraging results in this area to date. The proposed study here would explore the use of centre-near multifocal design contact lenses to encourage eye growth, thereby reducing hyperopia. There are three elements to the programme of research: 1. The natural progression of axial eye growth and refractive error will be measured in spectacle wearing hyperopic and anisohyperopic subjects aged between 5 and <19 years. In other words, the natural growth of the eye will be followed without intervention 2. As a paired eye control study anisohyperopes aged between 8 and <16 years will be fitted with a centre-near multifocal design contact lens in their more hyperopic eye and a single vision contact lens in the fellow eye if required. The progression of axial eye growth and refractive error will be measured and compared 3. Subjects aged between 8 and <16 years with similar levels of hyperopia in each eye will be fitted with centre-near multifocal design contact lenses in each eye. The progression of axial eye growth and refractive error will be measured and compared to subjects in the natural progression study. The objectives of the study are to: • Understand the natural progression of axial eye growth and refractive error in hyperopes and anisohyperopes • Establish if axial eye growth and refractive error can be modified using centre-near multifocal design contact lenses in hyperopes and anisohyperopes to improve visual outcome.