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Y.-Z. Wang, S. E. Morale, R. Cousins, E. E. Birch; The Course of Development of Global Hyperacuity Over Lifespan. Invest. Ophthalmol. Vis. Sci. 2008;49(13):5845. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Global visual integration is fundamental to shape and face recognition. While the maturation of local visual function, such as resolution acuity, has been well documented, less is known about the change of global visual function with age. In this study, we determined the course of development for a global hyperacuity, the threshold for detecting the radial modulation of circular shape, over lifespan.
Three hundred normal subjects, age from 0.17 to 78 years old, participated the study (n=76, 57, 43, 25, 54, and 45 for age groups <=1yr, 2.5 to 5.9 yrs, 6 to 10 yrs, 10.1 to 20.9 yrs, 21 to 50 yrs and >50 yrs old, respectively). The detection threshold for radial deformation was determined using a 2AFC, preferential-looking protocol (for <= 1 yr old) or a 2AFC staircase paradigm, with maximum likelihood threshold estimation. Resolution acuity was also measured. The developmental course was described by a curve of 3 segments: the 1st is an exponential function (y=a+a1*(exp[-b1(x-c1)]-1)); the 2nd is a horizontal line (y=a); and the 3rd is a linear function (y=a+b3(x-c2)), where c1 is the age dividing the 1st and 2nd segments, and c2 dividing the 2nd and 3rd segments. This curve was used to fit the data of logMAR thresholds for global hyperacuity and for resolution acuity as a function of age.
Curve fitting reveals that global hyperacuity was 0.30 logMAR at 0.17 yrs of age, and improved rapidly to -0.56 logMAR at 5.4 yrs of age (0.17 logMAR per year improvement). Its continuing maturation became slower, reaching to -0.70 logMAR (the 95% up-limit of adults’ threshold) at 7.5 yrs of age, and to the mean adult level (-0.86 logMAR, a) at 20 yrs of age (c1). Global hyperacuity started to deteriorate from 60 yrs of age (c2) at the rate of 0.04 logMAR per decade (10*b3). In comparison, resolution acuity reached to 0.0 logMAR (20/20) at 5.2 yrs of age, and reached the adult level of -0.1 logMAR (a) at 11.5 yrs of age (c1). Resolution acuity started to decrease from 55 yrs of age (c2) at the rate of 0.06 logMAR per decade (10*b3).
Similar to vernier alignment acuity, global hyperacuity improves rapidly during infancy and early childhood but takes longer to reach the adult level than resolution acuity. The delayed maturation of global hyperacuity suggests that further development to refine neural circuitry at the cortex level takes place in the second decade of life.
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