Visual, ocular and refractive development in children

Abstract

AbstractPurpose To describe visual, ocular and refractive development in children, possible reasons for deviations and some of the underlying mechanisms.Methods Literature review and own data.Results Contrast sensitivity and visual acuity develop slowly, reaching adult‐like performance around 5 years of age. Refractive development is very different if measured with and without cycloplegia but typically emmetropization was successful at 5 years of age, before the risk of myopia comes in. These developments require continuous visual feedback. If the retinal image is not focused or clouded by cataract, irreversible amblyopia develops. Eye growth represents by no means a linear scaling of the initial ocular dimensions. The decline in optical power of the cornea levels off already in the second year of life but axial eye growth continues at least until puberty. There is a built‐in risk factor for myopia because the crystalline lens has limited capacity to compensate for further axial elongation. These observations do not explain the environmental input to myopia development. In animal models, further axial eye growth is triggered by negative defocus, loss of image contrast, or abnormal light cycles or intensities. The retina is the major controller of axial eye growth. It uses image focus to control the growth of the underlying sclera bi‐directionally, depending on sign of defocus. Growth inhibition, induced by positive lenses, involves a biochemically different mechanism which is very responsive ‐ but can apparently still not save the human eye from myopic.Conclusion A lot can go wrong during postnatal ocular development since appropriate visual input is obligatory for normal development. Natural eye growth patterns include a built‐in risk factor for myopia development in early adolescence.