Color vision defect


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Color vision defect

  1. 1. Defective Color VisionGauri S. Shrestha, M.Optom, FIACLE
  2. 2. Color Vision Deficiencies Monochromacy Only one Pigment Type is present Dichromacy Only two Pigment Types are present Trichromacy All three Pigment Types are present
  3. 3. Monochromacy-Shades of Gray 3 Types Rod Monochromats • Most Common Type: 10 in 1 million people • No cones, very poor visual acuity Blue Cone Monochromats • Colorblind in photopic and scotopic conditions • Narrow range of mesopic conditions that they are not colorblind Cone Monochromats • Rarest Type: Only 1 in 100 million people • Acuity is fine during photopic conditions Patients learn to label colors by other cues
  4. 4. Monochromats These patients can match any wavelength in the spectrum by changing the intensity of another wavelength Termed: COLOR BLIND Poor Visual Acuity Sunglasses are a must! Depending on rod system for vision
  5. 5. Monochromacy10/1,000,000 - rod vision only Only see shades of lightness S M L Also poor visual acuity ROD 70 0
  6. 6. Dichromacy-2 Pigment Types More common than Monochromacy 3 Types Protanopia-Missing long wavelength (red) pigment Deuteranopia-Missing middle wavelength (green) pigment Tritanopia-Missing blue pigment
  7. 7. Dichromacy• Protonopia S+ L+M+S+ L+ – No L cone; X linked L-M- L-M-S- M- – 1% males, 0.02% females• Deuteranopia S M L – No M cone; X linked – 1% males, 0.01 %females• Tritanopia – No S cone; Autosomal dominant – 0.002% males, 0.001% females
  8. 8. Neutral Points The wavelength where the two remaining pigments cross Colors look very desaturated and whitish Patients cannot distinguish colors in this area of the spectrum • Colors at this wavelength are perceived as gray
  9. 9. Dichromatic Neutral Points
  10. 10. Trichromacy-3 Pigment Types There is no ‘neutral point’ 3 Types Protanomaly-shifted red pigment Deuteronomaly-shifted green pigment Tritanomoly-shifted blue pigment
  11. 11. Anomalous Trichromat• L&M pigment spectra shifted closer together S M L Match colors differently from ROD normal trichromats Some colors less discriminable 70 0
  12. 12. Hereditary Color Vision DefectsDEFECT PREV. IN MALES TRANSMISSIONDeuteronopia 1% X-linked recessiveProtonopia 1% X-linked recessiveDeuteronomaly 5% (Most Common) X-linked recessiveProtonomaly 1% X-linked recessiveTritanopia & .005% (Most Rare) Autosomaltritanomaly Dominant
  13. 13. Replacement model of Dichromacy Missing photopigment is replaced by a remaining photopigment Deuteranope: chlorolabe is replaced by erythrolabe Protanope: missing erythrolabe is replaced by chololabe Exception: missing cynolabe is not replaced by another photopigment
  14. 14. M-cone displaced toward L-cone displaced towardlong wavelengths short wavelengths
  15. 15. Spectral sensitivity: ChromaticSystem Presentation: Large stimuli (1°) and long duration (200msec) background moderately bright (1000 trolands)
  16. 16. 440 520 620nm nm nm
  17. 17. Spectral sensitivity: LuminanceFunction 660nm
  18. 18. Wavelength Discrimination Wavelength discrimination= absent Color discrimination= 545 luminance profile 490
  19. 19. Wavelength Discrimination Wavelength discrimination at longer wavelength Poor wavelength discrimination at 495nm
  20. 20. Color confusion lines Green=reddish purple Essential monochromat above 545nm
  21. 21. Color confusion lines Red-green confusion Essential monochromat above 545nm
  22. 22. Color confusion lines Confusion b/w Blue- violet & yellow
  23. 23. Saturation Neutral point: desaturated appearance of spectral stimuli at specific wavelength 570nm
  24. 24. Saturation
  25. 25. Color labeling 4 9 5 9 0 0 Color labeling is remarkably good in color vision deficiency However, Industrial color labeling is difficult, such as stripe/pattern analysis
  26. 26. Color Vision and Females Tend to be carriers Tend to have normal color vision 20 times less likely to have a color vision deficiency
  27. 27. Transmission of X linked, red-greendefects from parents to offspring X X X X X XX XX  X X Y XY XY Y XY XY Father Normal (XY) Father Defective ( Y) Mother Normal (XX) Mother Normal (XX)
  28. 28. Transmission of X linked, red-greendefects from parents to offspring    X X X X   X Y Y Y Y Y XY Father Normal (XY) Father Defective ( Y) Mother defective ( ) Mother Normal ( X)
  29. 29. Transmission of X linked, red-greendefects from parents to offspring  X X X XX Y Y XY Father Normal (XY) Mother carrier ( X)
  30. 30. Congenital vs. Acquired CONGENITAL ACQUIREDAffects both eyes equally One eye only OR asymmetricUsually a R-G defect B-Y OR R-GOther visual functions normal Other visual functions abnormalStable through lifetime Variable, dependant on test and diseases conditionsLearned to adapt-can label Cannot name color correctlyobjects
  31. 31. Congenital vs. Acquired CONGENITAL ACQUIREDMore prevalent in male Equally prevalent in male and femaleNot associated diseases or Classification nottoxicity straightforward with standard clinical color test
  32. 32. Kollner’s Rule Outer retinal diseases and media changes result in blue- yellow color vision defects Inner retina, optic nerve visual pathways and visual cortex diseases result in red-green defectsLocation Defect conditionMedia B-Y Nuclear sclerosisOuter retina B-Y AMD, DRInner retina R-G Optic atrophy, toxic amblyopiaPathway R-G Lesions
  33. 33. Chromatopsia These patients have no trouble distinguishing wavelengths, but perception of colors is altered Similar to wearing a filter over the eyes May occur in patients taking various medications Xanthopsia-slightly yellow tint (Digitalis) Cataract Formation • Patients notice blue tint upon cataract removal
  34. 34. We can measure2. the reflectance of an object2. brain responses3. behavioral responsesBut we can only guess whether your sensations are really the same as mine …
  35. 35. Kollner’s Rule BE CAREFUL-IT DOESN’T ALWAYS WORK Blue-Yellow Defects Associated with outer-retina problems (diseases that effect the photoreceptors) Ocular Media-Cataracts Red-Green Defects Associated with inner-retina problems (ganglion cells and visual pathways to the brain
  36. 36. LOCATION DEFECT CONDITION Media Blue-Yellow Nuclear SclerosisOuter Retina Blue-Yellow ARMD Diabetic RetinopathyInner Retina Red-Green Lebers Optic Pathways Atrophy Toxic AmblyopiaInner Retina Red-Green Lesions Pathways