The refractive state of the eye changes as the eye’s axial length increases and the cornea and lens flatten. In general, eyes are hyperopic at birth, become slightly more hyperopic until approximately age 7 years, and then experience a myopic shift until reaching adult dimensions, usually by about age 16 years (Fig 15-1). Emmetropization in the developing eye refers to the combination of changes in the refractive power of the anterior segment and in axial length that drive the eye toward emmetropia. The reduction in astigmatism that occurs in many infant eyes and the decreasing hyperopia that occurs after age 6–8 years are examples of emmetropization.
Race, ethnicity, and heredity play a role in the risk of particular types of refractive error. For example, myopia is more common among African American children compared with Hispanic children and non-Hispanic white children. Hyperopia is more common among non-Hispanic white children compared with African American and Hispanic children. Astigmatism is more common among Hispanic children and African American children than non-Hispanic white children.
Myopia is increasingly prevalent worldwide, and it is estimated that by 2050, 50% of the world population will be myopic. If myopia develops before age 10 years, there is a higher risk of eventual progression to myopia of 6.00 D or more. The etiology of increased myopia prevalence is unclear, but urbanization, increased near work, and decreased exposure to ultraviolet light are suggested influences. Low-dose (0.01%) atropine has been shown to significantly decrease myopic progression in Asian children.
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Chia A, Chua WH, Cheung YB, et al. Atropine for the treatment of childhood myopia: safety and efficacy of 0.5%, 0.1%, and 0.01% doses (Atropine for the Treatment of Myopia 2). Ophthalmology. 2012;119(2):347–354.
Holden BA, Fricke TR, Wilson DA, et al. Global prevalence of myopia and high myopia and temporal trends from 2000 through 2050. Ophthalmology. 2016;123(5):1036–1042.
McKean-Cowdin R, Varma R, Cotter SA, et al; Multi-ethnic Pediatric Eye Disease Study and the Baltimore Pediatric Eye Disease Study Groups. Risk factors for astigmatism in preschool children: the Multi-ethnic Pediatric Eye Disease and Baltimore Pediatric Eye Disease Studies. Ophthalmology. 2011;118(10):1974–1981.
Figure 15-1 Change in mean refractive error as a function of age.
(Modified with permission from Eustis HS, Guthrie ME. Postnatal development. In: Wright KW, Strube YNJ, eds. Pediatric Ophthalmology and Strabismus. 2nd ed. New York: Springer-Verlag; 2003:49.)
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.