title: Red light increment threshold as a measure of deficient color vision.
abstract: OBJECTIVE
  People with deficient red/green color vision have both poor color discrimination and are also insensitive to colored lights, especially red, in an increment threshold situation. In this study we compare detection thresholds for a long wavelength increment to two standard color discrimination tests.
  
  
  METHODS
  Forty-five color normal subjects and 19 color-deficient subjects (CDs) (12 deutans, 4 protans, and 3 unclassified) were tested with the Hardy-Rand-Rittler (HRR) plate test (4th edition), Farnsworth D-15 arrangement test and a long wavelength increment threshold test, i.e., the red test.
  
  
  RESULTS
  All CDs were less sensitive to the red increment than any of the normal subjects. The red test identified all CDs. There were no significant correlations between the red test results and the HRR test or the Farnsworth D-15 test.
  
  
  CONCLUSIONS
  The red test measures red light increment threshold, a characteristic of color vision not assessed by conventional tests of color vision which are based upon measuring loss of color discrimination. All CD observers have raised red light increment thresholds and the test clearly differentiates CD observers from those with normal color vision.
authors.affiliation: Department of Vision Sciences, School of Optometry, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
authors.forename: Yancy C
authors.initials: YC
authors.lastname: York
authors.forename: Michael S
authors.initials: MS
authors.lastname: Loop
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D003118:Color Perception / Q000502:physiology*; D003117:Color Vision Defects / Q000175:diagnosis / Q000503:physiopathology*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D010775:Photic Stimulation; D012684:Sensory Thresholds / Q000502:physiology