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Clinical Skills Year 2 > Colour vision tests > Flashcards

Colour vision tests Flashcards

1
Q

what is a protan described as

A

a general term stating that the long cone photo-pigment is different from normal

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2
Q

what is a deutan described as

A

a general term stating that the medium cone photo-pigment is different from normal

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3
Q

what is a tritan described as

A

a general term stating that the short cone photo-pigment is different from normal

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4
Q

what is the name if someone who has a missing long/L photo-pigment cone

A

protanope

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5
Q

what is the name if someone who has a missing medium/M photo-pigment cone

A

deutranope

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6
Q

what is the name if someone who has a missing short/S photo-pigment cone

A

tritanope

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7
Q

what is the name if someone who has one of their L, M or S cones missing

A

dichromat

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8
Q

what is the name if someone who has all three cones S, M and L present, but one is anomalous (different from normal)

A

trichromat (S, M or L spectral sensitivity is anomalous)

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9
Q

what is is called if someone has an anomalous L cone spectral sensitivity

A

protanomalous

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10
Q

what is is called if someone has an anomalous M cone spectral sensitivity

A

deutranomalous

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11
Q

what is is called if someone has an anomalous S cone spectral sensitivity

A

tritanomalous

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12
Q

what is a normal trichromat

A

there are 3 cones with L, M and S in the ‘normal group’

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13
Q

what is a cone monochromat

A

when two cones are missing

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14
Q

what is a rod monochromat

A

when all three cones are missing

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15
Q

list the three main colour vision tests

A
  • ishihara
  • anomoloscope
  • 100 hue and D15
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16
Q

which type of plates does the ishihara test use

A

pseudoisochromatic plates

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17
Q

which colour vision test uses colour matching

A

the anomoloscope

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18
Q

which test uses confusion lines

A

100 hue and D15

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19
Q

what is the general layout of the ishihara test plates

A
  • groups of spots with similar hues and lightness seen as a number or symbol
  • confusions affect the shape seen
20
Q

what are the 3 main advantages of the ishihara test

A
  • quick, simple and cheap
  • screens main deficiencies
  • good sensitivity and useful specificity
21
Q

how many plates are in a ishihara test

A

38 plates

22
Q

how many errors will most normals make with a ishihara test

A

less than 5 (0-5)

23
Q

hw many errors will a RGD make with a ishihara test

A

9 or more errors

24
Q

what is the lighting recommendation when testing with the ishihara test

A

300 - 500 lux

excellent colour rendering e.g. 
- north sky daylight 
or 
- standard illuminant D65
 or
- macbeth lamp
25
Q

which lighting conditions are not idea when testing with the ishihara test and why

A

tungsten, LED and fluorescent lighting

to avoid disadvantaging the subject with low levels of colour rendering

26
Q

list the 4 types of patients that the ishihara test is used on

A
  • all new patients
  • children
  • to see if occupational tests are required
  • general use for reports of colour disturbance, pathology and medication
27
Q

what is plate 1 of the ishihara test and who is it seen by

A

a demonstation plate - seen by all observers

28
Q

what are plates 2-9 of the ishihara test and who is it seen by

A

transformation plate - detected by normals but not RGDs

29
Q

what are plates 10-17 of the ishihara test and who is it seen by

A

vanishing digit - detected by normals but not RGDs

30
Q

what are plates 18-21 of the ishihara test and who is it seen by

A

hidden digit - not detected by normals but seen by RGDs

31
Q

what are the plates 22-25 of the ishihara test and who is it seen by

A

it is used to differentiate between protan and deutan

32
Q

which type of colour deficient people does the ishihara test for and which types are not detected

A

detects of red-green colour deficients (RGDs)

not tritan defects (but this is not a serious drawback)

33
Q

what is a disadvantage to the ishihara plate test

A

unable to differentiate reliably between whether its anomalous trichromats or dichromats

34
Q

if a fire fighter fails the ishihara plate test, what is the next test that needs to be carried out

A

farnsworth D15

35
Q

if a firefighter fails the farnsworth D15 test, what is the next test that needs to be carried out

A

nagel anomoloscope

36
Q

which type of cone photo-pigment abnormality will not be suitable for fire fighting

A

protan or deutan (red or green deficiency)

37
Q

what is the concept of the nagel anomaloscope

A
  • a yellow (589nm) is matched with a mixture of red (670nm) and green (546nm)
  • this is a standard RGB match but no blue primary, B is required (=zero)
38
Q

what must the subject do in a nagel anomaloscope test

A

adjust the proportions of R and G and the brightness of the yellow

39
Q

what is the indicator of someones colour vision with the nagel anomaloscope test

A

the chosen R/G and Y

40
Q

which types of patients is the nagel anomaloscope good at idenifying

A
  • normals
  • anomalous protans and deutrans
  • dichromat protans and deutrans
41
Q

how is the farnsworth D15 test used

A

subject places 15 caps of a munsell value 5 and chroma value 4 in order

the results are plotted onto a circular diagram P, D and T the subjects makes errors along the confusion axis

42
Q

which types of colour vision anomalies does the ishihara plate test detect

A

protan and deutan screening (either anomalous or dichromat)

43
Q

what is the main justification of optometric screening of colour deficiencies

A

to inform the subject of their problem in time and to give appropriate advice

44
Q

list 2 reasons for normal age related colour changes

A
  • yellowing of the ocular media (nuclear cataract)

- changes in retinal sensitivity

45
Q

list the non age related causes of colour deficiencies and what is affected in particular with these

A

arise from:

  • ocular disease
  • trauma
  • medication
  • exposure to toxic substances
  • commonly affect one eye or more
  • affects males and females equally
  • often affects blur perception (so is easily missed in many CV tests as they mainly screen red-green defects)

Clinical Skills Year 2 (20 decks)

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