The effect of normal development and aging on low-level visual field asymmetries M Loureiro, O C d’Almeida, C Mateus, B Oliveiros, M Castelo-Branco |
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IBILI, Faculty of Medicine, University of Coimbra, Portugal
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| It is well known that aging affects contrast sensitivity (CS) but its relation with changes in visual field asymmetries is still poorly understood. We have previously documented low-level interhemispheric (left/right), superior/inferior and retinal (nasal/temporal) anisotropies based on psychophysical/structural measurements. Our main goal was to explore these asymmetries in normal development using achromatic CS tasks, which probe distinct spatiotemporal frequency channels. Monocular CS was measured using intermediate (ISF: 3.5 cycles per degree (cpd) and 0 Hz; 303 eyes; 7-72 years, sampled in five age groups) and low spatial frequency tasks (LSF: 0.25 cpd undergoing 25 Hz counterphase flicker; 311 eyes; 10-83 years). Using ISF, left/right asymmetry was found only for young adults (p=0.002) and superior/inferior asymmetry was not present in children but increased with aging, with enhancement of inferior hemifield advantage (p<0.001). Retinal asymmetries were present across age groups with nasal hemifield advantage. Concerning LSF, children and older subjects did not exhibit cortical hemifield asymmetries; adolescents/adults showed only retinal asymmetries (p=0.005). We conclude that visual asymmetries with a direct ecological meaning (up/down at the highest spatial frequency) emerge during development and aging whereas retinal forms of anisotropy tend to stabilize or decline, while interhemispheric asymmetries are more specific to young adults. |
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