#11. Colour vision. Theories and disturbancies. Flashcards
What is COLOUR SENSE?
Faculty that helps us DISTINGUISH BTW DIFFERENT Colours, INFLUENCED BY:
a. Wavelength
b. Brightness
c. Saturation
What is COLOUR VISION?
AKA Trichromatic = Red / Green / Blue
- Basis of YOUNG-HELMHOLTZ Theory
What are the 5 THEORIES Used to Test for COLOUR VISION?
1) ISHOCHROMATIC CHART
- Coloured LITHOGRAPHIC Plates, where bold numbers are REP as DOTS of Various Colours
E.g. ISHIHARA LITHOGRAPHIC Plates
- Px who is Colour BLIND will find it DIFFICULT to identify these numbers
2) LANTERN TEST
- Colours are shown by a LANTERN
- EDRIGE-GREEN’s LANTERN
- Record the mistakes the Px makes
3) HOLMGREN’s WOOL
- Selections of SKEINS of COLOURED Wools
- Px is required to MAKE A SERIES of COLOURED MATCHES
4) NAGEL’s ANOMALOSCOPE
- BRIGHT DISC = Yellow / Red / Green
5) FARNSWORTH-MUNSELL 100 HUE TEST
- Shows HUE DISCRIMINATION by an ERROR
What is a DISTURBANCE for COLOUR VISION?
COLOUR BLINDESS = Achromatopsia
What is COLOUR BLINDNESS / ACHROMATOPSIA?
INABILITY to recognise Colour
- 1% in Males
- 0.4% in Females
What are the TYPES of CAUSES for COLOUR BLINDNESS?
1) Congenital
2) Acquired
What are the CONGENITAL CAUSES of COLOUR BLINDNESS?
And Types.
Where there’s ABSENCE of Red, Blue, or Green Pigments in CONES
- Inherited VIA Females
- Bilateral
- Incurable
A) PARTIAL
- Px CANNOT recognise Green (Most Common) / Red / Blue
- ABSENCE of 1 OR 2 of PHOTOPIGMENTS in FOVEAL CONES
B) TOTAL
- Px CANNOT recognise ANY Color
- Sees EVERYTHING as grey
- Rare
- Associated with NYSTAGMUS + CENTRAL SCOTOMA
What are the ACQUIRED CAUSES of COLOUR BLINDNESS?
- DUE to DISEASES of MACULA + OPTIC NERVE
E.g. Macular Degenerations, Toxic Ambylopia’s
- BLUE Blindness occurs in SCLEROSING Black Cataracts
What are the 3 TYPES of COLOUR BLINDNESS?
Explain them.
1) PROTANOPES = RED Sensation is DEFECTIVE
2) DEUTERANOPES = GREEN Sensation is DEFECTIVE
3) TRITANOPIA = ASBENCE of Blue Sensation (RARE!)
