title: The effect of age on the area of complete spatial summation for chromatic and achromatic stimuli.
abstract: OBJECTIVE
  Previously, an association between the area of complete spatial summation (Ricco's area) and age under scotopic conditions had been found. The authors sought to determine whether Ricco's area is similarly associated with age under photopic achromatic and selective S-cone conditions in peripheral vision and whether any association relates to a loss of ganglion cell density as determined by measurements of peripheral grating resolution acuity.
  
  
  METHODS
  Achromatic spatial summation functions were plotted for 68 healthy subjects (aged 20-77 years) in four oblique meridians on a gray background field of 10 cd/m(2). Similar functions were generated for the S-cone pathway (isolated using Stiles' two-color threshold method) for the same locations. Ricco's area was determined using two-phase regression analysis. Achromatic peripheral grating resolution acuity was measured at the same locations using high-contrast Gabor stimuli, as an estimate of localized functional ganglion cell density.
  
  
  RESULTS
  There was a notable decrease in overall contrast sensitivity with age for all stimulus sizes. However, there was no evidence of age-related change in Ricco's area for either achromatic (superior field, r(2) = 0.05; inferior field, r(2) = 0.0007; all P > 0.05) or chromatic (superior field, r(2) = 0.01; inferior field, r(2) = 0.006; all P > 0.05) stimuli, despite a significant decrease in peripheral grating resolution acuity with age (superior field, r(2) = 0.15; inferior field, r(2) = 0.17; both P < 0.05).
  
  
  CONCLUSIONS
  An age-related decline in functional ganglion cell density is not accompanied by a significant change in Ricco's area for achromatic or chromatic stimuli.
authors.affiliation: School of Biomedical Sciences, University of Ulster, Coleraine, Northern Ireland, United Kingdom. tony.redmond@moorfields.nhs.uk
authors.forename: Tony
authors.initials: T
authors.lastname: Redmond
authors.forename: Margarita B
authors.initials: MB
authors.lastname: Zlatkova
authors.forename: David F
authors.initials: DF
authors.lastname: Garway-Heath
authors.forename: Roger S
authors.initials: RS
authors.lastname: Anderson
mesh_terms: D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D002452:Cell Count; D055253:Color Vision / Q000502:physiology*; D015350:Contrast Sensitivity / Q000502:physiology; D006801:Humans; D008875:Middle Aged; D017949:Retinal Cone Photoreceptor Cells / Q000502:physiology*; D012165:Retinal Ganglion Cells / Q000473:pathology; D042262:Retinoscopy; D012684:Sensory Thresholds / Q000502:physiology*; D058609:Visual Field Tests; D014794:Visual Fields / Q000502:physiology; D055815:Young Adult