Course of development of global hyperacuity over lifespan

Global visual integration is fundamental to shape and face recognition. Although the maturation of local visual function, such as resolution acuity, has been well documented, less is known about the changes in global visual function during development and with aging.

Two hundred thirty-six normal subjects, ranging in age from 0.25- to 78-years old, participated in the study. Global hyperacuity (detection threshold for radial deformation) was obtained from 300 eyes using either a computerized testing or a chart testing protocol and spatial forced choice (preferential looking for <2.6-year old, pointing for young children, or verbal response for older children and adults). Resolution acuity was also measured. The developmental courses for global hyperacuity and resolution acuity were fit to a 3-segment curve to capture the initial rapid development, followed by a period of stable, adult-level visual function and, finally, the decline in visual function with aging.

Curve fitting revealed that global hyperacuity was 0.25 logMAR at 0.25 years of age, and improved rapidly to -0.56 logMAR at 5.4 years of age but did not reach the mean adult level (-0.86 logMAR) until 21 years of age. Global hyperacuity started to deteriorate from 55 years of age at the rate of 0.035 logMAR per decade. In comparison, resolution acuity reached 0.0 logMAR at 5 years of age, and reached the adult level of -0.1 logMAR at 11 years of age. Resolution acuity also started to decrease from 55 years of age at the rate of 0.058 logMAR per decade.

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 cortical level takes place in the second decade of life.