title: Spatial summation, contrast threshold, and aging.
mesh_terms: D000328:Adult; D000368:Aged; D000375:Aging; D005556:Form Perception / Q000502:physiology; D006801:Humans; D012160:Retina / Q000502:physiology*; D014792:Visual Acuity; D014796:Visual Perception / Q000502:physiology*