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64 Cards in this Set
- Front
- Back
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Define: colour vision
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the ability to perceive and discriminate between light on the basis of wavelength composition
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Give an example of radiation considered to have LOW WAVELENGTH
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low wavelength = high energy
x-rays gamma rays, UV rays |
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give examples of high wavelength radiation
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broadcast, infrared
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How many types of receptor in the retina are responsible for colour perception??
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3 - R, G, B
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What happens when all 3 colour receptors are equally stimulated in retina?
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white light is perceived
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What is the Young-Helmholtz theory?
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Any colour can be generated simply by the superimposition of pure red, green and blue light
* at retinal level |
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What are the 3 primary colours of paint? Is it true that they behave the same way as light?
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cyan, magenta, yellow
NO |
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What did Ewald Herring introduce to modify the Helmholtz theory?
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He suggested instead of having 3 types of receptors in the retina (helmholtz), that at the cortical level there are 3 pairs of receptors: B/Y, G/R, and Black/white and whichever out of the pair is stimulated more then that is the one which is seen
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What is the general belief about the theory of colour vision today?
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combo of helmholtz and herring. (retinal and cortical/optic nerve)
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What photopigments exist in each type of cone in the retina?
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red: erythrolabe
green: chlorolabe blue: cyanolabe |
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How far (in degrees) in the field is colour seen?
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90 degrees
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Define: Hue -
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what we normally refer to as "colour"; the extent to which something is a certain colour
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what is saturation? what does it depend on?
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the strength of a colour
depends on the amount of white or black in mix |
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what is a saturation level?
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high saturation = high number
ex. sat of 8 higher than sat of 2 |
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what os brightness?
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luminance of a colour. 0 = blaCK, 10 = white
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what are the prefixes for colour deficiences?? (red, green and blue)
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prot = red
deut = green trit = blue |
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what suffix refers to a partial deficiency? complete?
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anomaly = partial
anopia = complete |
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WHAT Is the term for a pt who has a complete red defect
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protanopia
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what is the term for a pt who has a partial blue defect
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tritanomaly
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what is the most common type of colour defect
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anomalous trichromats: 2/3 cones function normally but 1 is abnormal
*doesnt affect acuity |
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someone with a protanomaly sees red weakly. what is their probable deficiency? what colors do they tend to confuse?
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tan, olive brown (esp brown)
deficient in erythrolabe |
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someone with a deutanomaly sees green weakly. what is their probable deficiency? what colors will they confuse?
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confuse between pink/dull green, tan/olive, brown
chlorolabe deficient |
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what is the most rare type f color anomaly?
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tritanomaly
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What is a dichromat?
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only 2 types of photopigment are available
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Why do some believe that anomalous trichromats and dichromats are essentially the same?
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believe that in dichromats, all 3 photopigments are present but one is acting soooo sub-optimally that it is considered as barely present or not present.
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What is a monochromat or achromat? what are the types
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1. rod monochromat (complete achromats) - pt only has rhodopsin pigment acting, and reduced number of cones. ~20/70 and worse acuity
2. Blue cone monochromats (incomplete achromats) only have cyanolabe pigment (blue cones) can see blue, yellow, grey |
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What is the inheritance pattern of a protan defect? deutan?
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both X-linked recessive
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If mom is a carrier of protan defect and dad is affected with the same defect, what is the chance that they will have an AFFECTED son? A CARRIER daughter?
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affected son: 25%
carrying daughter: 25% |
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If mom is unaffected, but dad is affected with a deutan defect, what is the chance they will have an AFFECTED son? A CARRIER daughter? AN AFFECTED daughter?
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0%
0% 50% |
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What is a common reason for developing an acquired colour defect?
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drug toxicity
also, ocular or systemic disease |
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List soem ocular or systemic diseases that can cause colour vision defects
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Optic Nerve Disease
Retinal Disease Stargadt's Disease (Macular degeneration) Macular Degeneration Macular Dystrophies Inflammation Vascular hypertension Diabetes |
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Acquired retinal defects usually result in what tyype of defect
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blue/yellow
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True or false: A pt who makes errors over one specific area of the colour wheel has an acquired colour vision defect.
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false. congenital: specific areas. acquired: all ovaaa
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Other visual entities (acuity etc) are normal in what type of colour defect?
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congenital
other abnormalities usually present in acquired defect |
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What are the characteristics of a congenital colour vision defect?
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- errors made in specific areas of colour wheel
- other visual functions normal - reproducible test results - stable defect - symmetrical defect - pt names colours correctly |
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What are the characteristics of an acquired colour vision defect?
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- pt makes errors all over wheel
- other visual abnormalities are usually present - test results not reproducible (may vary) - defect may progress or regress - often asymmetric - may name colours incorrectly |
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What is Kollner's rule?
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congenital colour defective ppl make mistakes only in specific areas of the couluour whell. acquired make mistakes all over the wheel.
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Name the 4 types of colour vision tests.
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1. Lantern - simulate colour tasks under working conditions
2. Pseudo-isochromatic plates - colour figures embedded in a bg 3. Sorting/Arranging - colour caps arranged accorindg to colour 4. Anomaloscope - requires mixing of colours to match a control |
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How can you differentiate between an acquired an congenital defect (during testing)?
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test monocularly
(????????? why ?? i have no idea) |
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What is the Holmgren wool test
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3 large skeins of wool and 72 small ones (12 diff colours); 5 match the controls and 7 are confusng colours
pt matches similar colours to controls |
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What is the APT-5 colour vision test
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automated - illuminated pseudo-isochromatic plates. Uses HOTV letters; supposed to simulate results of anomaloscope. timed stimulus presentation
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What is the farnworth panel d-15?
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designed for CONGENITAL defects; especially dichromats
- single fixed chip and 15 moveable - saturation level 5 - dot to dot format on score sheet - normals form a circle - abnormals cross axis |
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Name the 4 types of colour vision tests.
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1. Lantern - simulate colour tasks under working conditions
2. Pseudo-isochromatic plates - colour figures embedded in a bg 3. Sorting/Arranging - colour caps arranged accorindg to colour 4. Anomaloscope - requires mixing of colours to match a control |
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How can you differentiate between an acquired an congenital defect (during testing)?
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test monocularly
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What is the Holmgren wool test
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3 large skeins of wool and 72 small ones (12 diff colours); 5 match the controls and 7 are confusng colours
pt matches similar colours to controls |
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What is the APT-5 colour vision test
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automated - illuminated pseudo-isochromatic plates. Uses HOTV letters; supposed to simulate results of anomaloscope. timed stimulus presentation
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What is the farnworth panel d-15?
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designed for CONGENITAL defects; especially dichromats
- single fixed chip and 15 moveable - brightness and saturation level 5 - dot to dot format on score sheet - normals form a circle - abnormals cross axis |
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what is desaturated D-15?
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- similar to farnsworth oanel d-15 but brightness increased to 8 and saturation decreased to 2
- designed primarily for aCquired |
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what s 100-Hue test
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- detects both congenital and acquired
- only 1-2% of normals can do this test and not mke any error - 93 coloured caps, 8 fixed in four trays - hood with lughts off in room - scoring card is retarded |
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How is scoring done on 100-Hue test
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correct order: 1 2 3 4 5
pt order: 2 1 3 4 5 difference: 3 2 1 1 cap score: 5 2 then cap score is plotted on circular grid; innermost = 2(lowest) error score: cap score - 2 total error score: = sum of all error scores on each line R: 46 G: 56 B: 66 |
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What is Lanthony new colour test
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- both congenital and acquired
- studies effects of hue, sat, brightness independenty - 4 boxes with 15 caps; range in saturation from 8 to 2 - 10 grey caps range in brightness from 4 to 8 - no fixed starting colour |
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describe the three types of scenarios which can occur with Lanthony new colour test.
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1. Pt leaves colours in with greys
2. Pt leaves greys in with colours *congenital* 3. Pt separates/sorts normally |
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In new Lanthony colour test, when does the pt sort the greys?
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last task (level 2 saturation) and only done if separation task is abnomal.
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How is scoring done in new lanthony colour test?
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separation score: (#mistakes)*(sat level)
score>10 = abnormal |
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What is precision vision (colour) test
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similar to d-15 but larger caps
more suitable for low vision pts or kids coated caps that dont stain |
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what is the ishihara test
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designed for congenital RED-GREEN DEFECTS
- pr detects a number embedded in bg of coloured dots (isochromatic test) |
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What is American-Optical-Hardy-Rand-Ritler
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DETECTS RED/GREEN AND BLUE/YELLOW
- pt told to detect shape or symbol embedded in variable grey dot background |
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What is the standardized isochromatic plates test
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- v similar to ishihara but it has calculator style numbers
Part 1: congenital Part 2: acquired not quantitative, tho |
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What is th city university test?
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four coloured dots surround a centre dot; pt matched one dot with the one int he middle
saturation varies (6 plates at sat=4 and 4 at sat = 2) |
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What is the Tritan album
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detects blue/yellow
square with an area cloured in pt tells which corner is coloured |
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describe the sloan achromatopsia test
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designed to see if pts can match colours to grey.
high saturation |
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describe anomaloscope test
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- gold standard
- congenital and acquired - based on mixing of 2 colours to form one - not good for low vision or children |
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describe guy's colour vision test
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for children
- ishihara style but with letters - matching set of letters supplied RED GREEN SCREENER ONLY this test sux because you dont even know what letters are intended sometimes |
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What is the best protocol to follow when assessing colour vision?
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battery of tests./ best is: New Colour. if not: then try precision vision, AOHRR or APT-5
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