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Russell J. Adams, Mary L. Courage; Do Optical Immaturities Account for the Early Limitations in Human Spatial Vision?. Journal of Vision 2004;4(8):774. doi: 10.1167/4.8.774.
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© ARVO (1962-2015); The Authors (2016-present)
During early infancy, spatial vision is very immature and infants possess relatively high levels of spherical (primarily hyperopic) and astigmatic refractive error. Although optical error is the primary contributor to impaired spatial vision in adults and older children, the role that “front end” immaturities play in infantile visual limitations has yet to be quantified. In the present study, we employ newly developed refractive technology to measure refractive error and visual acuity in individual infants, children, and adults.
Left eyes from 6-mo-old (n=28) and 12-mo-old (n=30) infants were refracted twice with the Welch-Allyn SureSight autorefractor (without cycloplegia), and assessed with the Teller acuity cards. For comparison, 3-4-yr-old preschoolers (n=56), 7–8 yr-old children (n=44), and young adults (n= 59) were refracted, and acuity assessed (uncorrected) with either Snellen letters (adults and children) or LEA symbols (preschoolers).
Calculations of total absolute refractive error[ |Sph| + |Cyl| ], spherical equivalent, and other linear models of aggregate refractive error all revealed consistent results: Levels of visual acuity in adults and children were predicted well from the magnitude of uncorrected refractive error (all r > 0.59, all p < 0.01). However, neither 6- nor 12-mo-old infants showed any relationship between acuity and refractive error (range or r = −0.08 to 0.06).
This is the first study to provide systematic developmental data on the relationship between spatial vision and refractive error from infancy to adulthood. In adults, older children, and preschoolers, spatial vision is predicted well by optical factors. Conversely, almost none of the variation in visual acuity among individual infants is accounted for by differences in optics. This supports current neurological and psychophysical models of visual development which propose that early spatial vision is constrained almost entirely by photoreceptoral and neural immaturities.
Natural Sciences and Engineering Research Council of Canada
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