NW2005 Color vision

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NW2005 Color vision

  1. 1. Color Vision ณวัฒน์ วัฒนชัย กิติกล ลีละวงค์ ุ
  2. 2. Visual process ht lig object light source refle ct e d ligh t/co lor eye
  3. 3. Electromagnetic spectrum
  4. 4. Visible light  normally visible light 400-700 nm  except : beta peak (380-400 nm)  infant  aphakic condition
  5. 5. color vision  how we can see all these colors?
  6. 6. AnaToMy
  7. 7.  Visual process     light pass through cornea/AC/lens/vit absorption by the rod/ cone photoreceptors retinal neural circuit  horizontal cells  bipolar cells  ganglion cells optic nerve higher visual centers  LGB (parvocellular portion)  Cortex
  8. 8. Rod and Cone photoreceptors
  9. 9. Rod and Cone photoreceptors <400 nm 400-700 nm >700 nm
  10. 10. Rod photoreceptors     92 millions (100M) no rod in central 0.25 mm of fovea peak at 5-7 mm from foveal center decrease number with age
  11. 11. Rod photoreceptors    mediate vision at low illumination levels (scotopic) 108 range of illumination from near darkness to daylight critical flicker threshold 20 Hz
  12. 12. Cone photoreceptors     4.6 millions (5M) highest density at macula stable numbers, no relationship to age Mediate best vision at daylight levels (photopic)
  13. 13. Cone photoreceptors    Responsible for good visual acuity and color perception 1011 range of illumination from moonlight nights to very very bright light critical flicker threshold 55-60 Hz
  14. 14. Rods and Cones together   Mesopic photopic + mesopic + scotopic = 1014 range of illumination
  15. 15. no rod in central 0.25 mm of fovea, peak between 5-7 mm from foveal center, while cone has highest density at macula  this distribution means  midperiphery of VF  the greatest light sensitivity (night vision)  fovea  high acuity, good color vision
  16. 16. Rod and Cone photoreceptors     Rod SWS cone MWS cone LWS cone (B-cone) (G-cone) (R-cone) 507 nm 445 nm 543 nm 566 nm
  17. 17. Gene Encoding the Human Photopigments chromosome 3  Rhodopsin  Iodopsin (SWS) chromosome 7 Iodopsin (MWS,LWS) chromosome X 
  18. 18. Cone cells S cones - longer inner segment larger inner segment deeper innervation patchwork mosaic low at fovea, peak 1 degree all ~ 10% L, M cones - very similar dense hexagonal packing L/M ~ 2/1 all ~ 90%
  19. 19. genes : L, M cones  located on chromosome X tandem array ~ 2-6 (1 LWS, >1 MWS) hybrid  protan (red-blind)  deutan (green-blind)
  20. 20. Horizontal cells 1. 2. 3. - H1 dendrite all cones-axon-rod H2 contact S cones avoid others H3 avoid S cones contact others local-circuit neurons chromatic organization opponent color coding first stage of wavelength discrimination ?
  21. 21. Bipolar cells For rod : on-cell type (single depol.) For cone : off and on-cell type Depolarize (on) : depol. Response to central/direct illumination Hyperpolarize (off) : hyperpol. To center illumination and depol. To surround illumination
  22. 22. Ganglion cells - - - Its axons form optic nerve and terminate at LGB/ other diencephalic centers/ superior colliculus earliest visual neuron to generate true action potential neural coding in term of frequency of firing spatial/color opponent organization functional classification P & M
  23. 23. Ganglion cells Property P cells color selectivity yes receptive field size small luminance contrast low cell size small conduction velocity low response time course tonic function in scotopic no number of cells 1,000,000 M cells no large (~10 times high large high phasic yes 100,000
  24. 24.  optic nerve  LGB  cortex/ other centers
  25. 25. Color vision 11 basic color term 4 uniques hue : red yellow green blue 3 achromatic color: black white gray other 4 color : orange purple brown pink
  26. 26. Basic Aspects of Color Vision human can perceived 8000 colors at a single luminance level  at optimal cone vision (1000  luminance range) – 8,000,000 sh ades and tints can be distinguishe d
  27. 27. Theory of color reception   theory of trichromacy theory of opponent color  opponent cells  double opponent cells
  28. 28. Color vision : color system 1 CIE color system Commission international del’Ecalirage specific luminance proportion x + y + z = 1 3 dimension 2 dimension spectral/non-spectral color white center
  29. 29. . W
  30. 30. Color vision : color system 2 Munsell color system - - cylinder - hue (spectral color) 10 x10 ( R Y G ) Circumferential - value (lightness) up/down - chroma (whiteness) radial
  31. 31. Factors that modified color vision       Brightness Saturation State of dark adaptation : Perkinje effect Adjacent cone : lateral inhibition Fatique and after image Optical factors : lens, macula, chromatic aberration, Stile-Crawford effect
  32. 32. Colorless objects that appear colored  Blue sky : blue – easier scattered
  33. 33. Colorless objects that appear colored  red sunset
  34. 34. Colorless objects that appear colored  blue water
  35. 35. Color Vision Defect what is color?!?!? moo.o..o...
  36. 36. Color Vision Defects Normal trichromats 92%  Dyschromatopsia 8% 
  37. 37. Classification of hereditary color defect red ano. Trichromats Protanomal Dichromats Monochromats Protanope green Deuteranomal blue Tritanomal Deuteranope Tritanope Blue cone monochromats Rod monochromats
  38. 38. Dyschromatopsia  Anomalous trichromatism  Protanomaly XR   XR Tritanomaly AD Dichromatism  Protanopia XR  Deuteranopia XR  Tritanopia AD Monochromatism  Rod monochromatism AR  cone monochromatism XR   Deuteranomaly 1% 5% 0.0001% 1% 1% 0.0001% 0.001% UK
  39. 39. Congenital red-green defect    most common male 8%, female 0.5% Cause  Deletion of R-G pigment gene  Hybridization of R-G gene
  40. 40. Congenital red-green defect
  41. 41. Congenital red-green defect  Characteristics  symmetrically binocular  constant in type and severity through out life  normal VA/ fundus/ photoERG  name the color correctly
  42. 42. HUE DISCRIMINATION DEFECT
  43. 43. Acquired color vision abnormality  Characteristics  VA & VF defect  Generally varied in type and severity  Unstable severity
  44. 44. Acquired color vision abnormality  charateristics  Affect one eye or asymmetrically affect  Use incorrect color name or report that familiar color appearance has changed
  45. 45. Acquired color-vision abnormality Kollner’ rule B/Y : retinal/choroid receptor/outer plexiform R/G : neural disorder ganglion cell
  46. 46. Kollner’s rule Retinal diseases : B/Y Eg: RD, RP, ARMD, myopic degen, chorioretinitis, CRVO, DR, CSCR Except : cone-dystrophy, Stargardt’s
  47. 47. Kollner’s rule Optic nerve diseases : R/G Eg: optic neuritis, ON compression, LHON, toxic optic neuropathy Except : AD optic atrophy, glaucoma, AION, OHT
  48. 48. Acquired/hereditary color defect characteristics - Color- naming - unilateral/bilateral - blue-yellow - change/ unstable - other visual symtoms
  49. 49. Color Discrimination    Hue Saturation (chroma) Brightness (luminance, intensity)
  50. 50. 1. Hue Discrimination     hue  wavelength depend on proportion of cone output better in intersected sensitivity function cross point of pigment absorption sensitivity yellow(590) red/green blue-green(490) green/blue
  51. 51. Hue Discrimination
  52. 52. 1. HUE DISCRIMINATION
  53. 53. 2.Saturation  color purity fully saturated color : only 1 wavelength for visible light  desaturated color : add white light  perception  depth of color (dark/ light blue) 
  54. 54. 2. Saturation Saturation - how much of one hue must be add to white to be distinguished - the more amount, the less saturation - many variables purity, intensity, size, time
  55. 55. 2. SATURATION SENSITIVITY yellow – lowest saturation
  56. 56. 3. Luminosity relative brightness/lightness peak absorption photopic 555 scotopic 507 Purkinje shift (rod & blue cone pathway?)
  57. 57. 3. LUMINOSITY CURVE 507 555
  58. 58. Color vision tests
  59. 59. Color vision tests Patient selection - screening test in children, student, worker - undiagnosed low vision - recent color disturbance - Family Hx of color defect - Occupations
  60. 60. Color vision tests  Ideal color vision test  Detect the presence or absence of normal color vision  Distinguish between R-G and B-Y defect  Assess the severity of defect  comfortable
  61. 61. Color vision tests 1. 2. 3. Screening test Color discrimination test Color matching test
  62. 62. Color vision test 1: screening test 1. Color confusion 1. Ishihara test 2. FD15 test 2. Color saturation 1. AO-HRR test 2.TMC plate
  63. 63. Color vision test : Ishihara test - Test R-G - High sensitivity for congen R-G defect
  64. 64. Color vision test : AOHRR test - 24 plates - Color defect or not - Assess severity (+/-) R-G and B-Y -
  65. 65. Color vision : FD-15 - Farnsworth D-15 - line of confusion - R/G,B/Y - separate color handicap
  66. 66. FD-15
  67. 67. FD-15
  68. 68. Color vision tests 1. 2. 3. Screening test Color discrimination test Color matching test
  69. 69. Color vision test 2 : discrimination    Hue discrimination  FM-100  Farnsworth desaturated panel D-15  Lanthony new color test Lightness discrimination  Verriest’s lightness discrimination Saturation discrimination  Sahlgren’s saturation test
  70. 70. Color vision test 2 : discrimination  ใช้เวลามาก  อาศัยความชำานาญ  ไม่เหมาะกับ routine exam  ไม่เหมาะกับเด็กอายุนอยกว่า 10 ปี ้
  71. 71. Farnsworth-Munsell 100 hue test - 85 caps in 4 groups hue discrimination test serial color order within 2 min /each group position&number of error score
  72. 72. FM 100 hue test  Goals  Grading of color discrimination in normal subjects (superior/ average/ low)  Find zone of color confusion
  73. 73. Farnsworth-Munsell 100 hue test
  74. 74. Color vision tests 1. 2. 3. Screening test Color discrimination test Color matching test
  75. 75. Color vision 3 : matching Anomaloscope 1. Nagel R/G red640 + green545 = yellow589 2. Pickford-Nicolson B/Y, R/G 3. Sloan’s achromatopsia test grading severity Expense
  76. 76. ไม่เ ห็น รู้เ รื่อ ง เลย...ย......... ?

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