title: Color vision deficits in intermediate age-related macular degeneration.
abstract: OBJECTIVE
  To assess the effect of intermediate age-related macular degeneration (AMD) on foveal cone-contrast thresholds.
  
  
  METHODS
  We measured L-M and S-cone-contrast thresholds in subjects with intermediate AMD (n = 10) and age-matched control subjects (n = 10). Monocular, foveal 3-degree Gaussian blobs (600-millisecond raised cosine) were presented at 16 cone ratios throughout L-, M-, and S-cone space, and threshold contours were modeled with probability summation between two independent detection mechanisms. The role that preretinal absorption plays in aging was also evaluated by simulation with FG15 and neutral-density filters.
  
  
  RESULTS
  Aging results in loss of neural sensitivity, not explained by lens changes. On average, intermediate AMD was associated with reduced sensitivity in both color and luminance channels (p < 0.05) that appeared to indicate greater involvement of S-cones. When data were normalized to age-expected values, the changes to cone sensitivity were shown to be consistent (∼200% loss) across L-M, M-L, and S-cone mechanisms. In comparison, the luminance (L + M) mechanism showed relative sparing (155% loss, p < 0.05).
  
  
  CONCLUSIONS
  Eyes with the same phenotype of intermediate AMD can have varying degrees of color threshold loss. Functional markers enhance the clinical definition of disease expression in AMD.
authors.affiliation: *BOptom, PhD, FAAO †BOptom, PhD ‡BScOptom, PhD, FAAO Department of Optometry and Vision Sciences, University of Melbourne, Victoria, Australia (all authors).
authors.forename: Laura E
authors.initials: LE
authors.lastname: Downie
authors.forename: Ada S
authors.initials: AS
authors.lastname: Cheng
authors.forename: Algis J
authors.initials: AJ
authors.lastname: Vingrys
mesh_terms: D000368:Aged; D055253:Color Vision / Q000502:physiology; D003117:Color Vision Defects / Q000503:physiopathology*; D015350:Contrast Sensitivity / Q000502:physiology*; D005260:Female; D006801:Humans; D008268:Macular Degeneration / Q000503:physiopathology*; D008297:Male; D017949:Retinal Cone Photoreceptor Cells / Q000502:physiology*; D012684:Sensory Thresholds