title: Functional characteristics of blue-on-yellow perimetric thresholds in glaucoma.
abstract: OBJECTIVE
  Blue-on-yellow (B-on-Y) perimetry assesses the S-cone visual field under yellow adaptation. Glaucomatous field defects have been shown to appear earlier and to be larger in B-on-Y perimetry than in standard perimetry. An upper limit to the use of B-on-Y perimetry is set by the separation of the S-cones from the M- and L-cones. But, because the S-cones may also input to the luminance channel, the actual separation of the color and luminance channels is unknown. Here, the relative sensitivities of the color and luminance channels under B-on-Y test conditions are measured.
  
  
  METHODS
  In 15 eyes with early glaucoma, 19 risk eyes, and 10 normal eyes, B-on-Y thresholds were measured from 0 degrees to 20 degrees eccentric and were compared to pure chromatic (B-in-Y) and achromatic (Y-on-Y) thresholds, obtained under identical yellow adaptation.
  
  
  RESULTS
  In normals, B-on-Y thresholds were found to coincide with B-in-Y thresholds; Y-on-Y values were 0.5 log (at 20 degrees) to 0.9 log (at 0 degrees) higher. In the pathologic groups, the differences between B-in-Y and Y-on-Y thresholds were smaller. Pathologic threshold elevation is on average 1.8 times larger for chromatic than for achromatic stimuli. In some cases, the luminance channel takes over detection of the B-on-Y stimulus.
  
  
  CONCLUSIONS
  In normals, the B-on-Y stimulus is mediated by the color channel. Takeover of detection by the luminance channel might impose limits on following color defects with B-on-Y perimetry. This takeover may occur before the S-cones become less sensitive than the M- and L-cones and might indicate S-cone input to the luminance channel.
authors.affiliation: Graduate School of Neurosciences, University of Amsterdam, Netherlands.
authors.forename: J
authors.initials: J
authors.lastname: Felius
authors.forename: L A
authors.initials: LA
authors.lastname: de Jong
authors.forename: T J
authors.initials: TJ
authors.lastname: van den Berg
authors.forename: E L
authors.initials: EL
authors.lastname: Greve
mesh_terms: D000368:Aged; D003118:Color Perception / Q000502:physiology*; D005260:Female; D005902:Glaucoma, Open-Angle / Q000503:physiopathology*; D006801:Humans; D007429:Intraocular Pressure; D008297:Male; D008875:Middle Aged; D009798:Ocular Hypertension / Q000503:physiopathology*; D017949:Retinal Cone Photoreceptor Cells / Q000502:physiology*; D012680:Sensitivity and Specificity; D012684:Sensory Thresholds / Q000502:physiology*; D058609:Visual Field Tests / Q000379:methods*; D014794:Visual Fields