Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Optometry class OP2501 > Colour Vision > Flashcards

Colour Vision Flashcards

1
Q

For the D-15 Dichotomous test, what is it used to assess? What does it involve?

A

-red green and blue yellow colour vision defects
-patient has to arrange coloured caps in a sequence which determines type and severity of colour vision defect

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are the conditions of the d-15 dichotomous test?

A

-px is sat so they’re viewing the caps from 50cm
-standard illuminant C instead of room lighting for illumination
-there’s no time limit
-caps are initially randomised

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What and how on the recording sheet shows severity of the defect in d15 dichotomous test?

A

The number of crossings:
-2 or less indicate moderate colour vision deficiency
-more than 2 indicate a severe colour vision defect

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What and how on the recording sheet shows severity of the defect in d15 dichotomous test?

A

The number of crossings:
-2 or less indicate moderate colour vision deficiency
-more than 2 indicate a severe colour vision defect

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

How does the recording sheet for d15 dichotomous test tell you the type of defect?

A

Orientation of the crossings indicate wether it’s a protan, deutan or tritan colour defect

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are the conditions of the city test?

A
  • px should view book at 35-50cm
    -use standard illuminant
  • allow up to 3 secs per page
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

In the city test what are part 1 and part 2 each for and what happens in them?

A

Part 1 is for screening and part 2 is for classification
-in part 1, Px has to work out if one of the three dots is a different colour and then identify which one is different
-in part 2, Px has to tell the examiner which of the 4 dots around the central dot is the same colour as the central dot

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How do you know if a patient has a colour deficiency and what type in the city test

A

-In part 1 if the px gets less than 8 correct then they have a colour deficiency
-In part 2 if they have any entries for protan, deutran and tritan then they may have a colour deficiency

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What pathologies behind colour defects is Ishihara good for detecting?

A

-maculopathies
-subtle optic neuropathies

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is a disadvantage of the ishihara test?

A

Not good at determining the severity of the defect

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is the ishihara test?

A

The most common test for detecting red-green colour deficiencies

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What are the conditions for the ishihara test?

A

-patient should view the book at 66-75cm
-use standard illuminant
-allow up to 4secs per page
-use 17 plates for screening: 1 demonstration, 1 transformation and 8 vanishing (only trichomats see)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How will anomalous trichromats see ishihara vanishing plates?

A

See an alternate digit (trichromats see nothing)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what are the three types of cones?

A

M cone = green cone = middle cone
L cone = red cone = long wavelength cone (most numerous)
S cone = blue cone = short wavelength cone (least numerous)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

how many cones do we have?

A

7 million

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what percent of each cone make up total cones in the retina

A
  • blue (S) = 5%
  • green (M) = 35%
  • red (L) = 60%
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what does univariance mean and what does this therefor suggest?

A

when all wavelength of info is lost when light hits one cone and reacts with the visual pigment hence a single cone cannot distinguish a specific colour as cones response is determined by number of photons absorbed instead of the specific wavelength of those photons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

what are the two colour vision theories?

A

-young/helmholtz trichromatic theory
-Herring opponency

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what does young/helmholtz trichromatic theory show

A

most colours in the visual spectrum could be matched with 2 other colours but 3 were needed in order to match every colour we can receive hence the conclusion that there are three primary colours

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

how does herring opponency theory contradict young/helmholtz trichromatic theory

A

as it concludes that there are three opponent mechanisms within our visual system where he proposed we have a blue vs yellow visual channel, a red vs green visual channel and a black vs white visual channel (bipolar channels)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

what is max wavelength absorption for each cone?

A

Blue = 440nm
green = 535nm
red = 565nm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

what connects the LGN to the higher cortical areas?

A

optic radiations

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

what are the 2 pathways from the retina to the LGN in the visual cortex? what are they each for?

A

-parvocellular pathway: R_G chromatic channel and achromatic luminance channel
-koniocellular pathway: B-Y Chromatic channel

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

in the visual cortex, where do neurones from koniocellular layers synapse and what are they called here?

A

in layer 3 called blobs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

in the visual cortex, where dol cells in the parvocellular layers synapse?

A

in layer 4C(beta) and then post synaptic projections to layer 3 to separate chromatic and achromatic info

26
Q

what happens in the red-green channel in herring’s opponency theory?

A
  1. Red and green cell receives excitatory input from the L cone receptor and inhibitory input from the M receptor
  2. Opponent cells have opponent receptive fields e.g. green on cells and red on cells
  3. When green on cell is excited, you perceive green and when it is inhibited, there is no perception
27
Q

what is the pathway for how colour is perceived starting from retinal ganglion cells

A
  1. Red green chromatic channel goes through parvocellular pathway in the lateral geniculate nucleus
  2. Blue yellow chromatic channel goes through koniocellular pathway in the lateral geniculate nucleus
  3. Optic radiations
    Visual cortex
    In visual cortex, the cells are organised into hypercolumns and each correspond to a point on the retina
  4. Neurons in koniocellular layers synapse in layer 3 (blobs)
  5. Neurons in parvocellular layers synapse in layer 4Cbeta
    Post synaptic projections go to layer 3
  6. Reaches the colour analysis destination
  7. Colour analysis destination contains info from blobs and interblobs
  8. This info is combined with form, texture and edge info which then contributes to overall perception
28
Q

what are the two types of colour vision defects?

A

congenital and acquired

29
Q

what are the 5 key functions of the visual cortex?

A

-feature detection
-colour processing
-depth perception
-motion detection
-object recognition

30
Q

what does it mean in terms of the visual cortex if a patient reports being able to see colour without form?

A

there is no input from interblobs

31
Q

compare and contrast congenital vs acquired colour defects

A

-congenital defects mainly affect males while acquired has equal prevalence in males and females
-both have onset after birth
-in congenital, the type and severity of the colour deficiency is constant whereas in acquired, the type and severity of the deficiency varies
-congenital is easy to classify while acquired is not
-congenital affects both eyes equally whereas acquired has monocular differences
-in congenital va and vfs are normal (apart from in monochromats) whereas in acquired, va and vfs may be affected

32
Q

why are congenital colour defects more common in males?

A

as they are X linked recessive inheritance

33
Q

what are the two types of congenital defects?

A

-where the cone is absent/ non functioning = dichromat
-cone has impaired sensitivity = anomalous trichromat

34
Q

what are the three types of dichromat?

A

-protanopia (L cone)
-deutreranopia (M cone)
-tritanopia (S cone)

34
Q

whats the most common congenital defects seen in practise?

A

red green defects
-protanopia and deuteranopia in males

34
Q

what are the three types of anomalous trichromats?

A

-protanomalous trichromat (L)
-deuteranomalous trichromat(M)
-tritanomalous trichromat (S)

35
Q

what kind of vision do protanopes have and how is that of deuteranopes different?

A

-protanopes have reduced sensitivity at long wavelengths so there’s dimming effects causing confusion with reds and blacks
-deuteranopes don’t experience dimming because they still have L cones where they can see longer wavelengths of light

36
Q

what colours may protanopes confuse?

A

red and black

37
Q

why is monochromacy rare? what is atypical monochromacy?

A

-as the gene which causes it is on chromosome 3 and it has a recessive inheritance pattern
-In atypical cone monochromacy, they only have s cones, VA is better than rod monochromacy

38
Q

what colours are protanopes not able to distinguish? what colours might they not be able to distinguish?

A

-red-yellow-green
-black or dark gray

39
Q

what colours are deuteranopes unable to distinguish?

A

red-yellow-green
(same as protanopes just without the dimming)

40
Q

what colours are patients with tritanopia unable to distinguish?

A

blue-green-yellow

41
Q

what do anomalous trichromats confuse?

A

pale desaturated colours but not bright and saturated ones

42
Q

what are the two types of monochromats?

A

-rod monochromats (achromatopsia) - no functioning cone cells
-cone monochromats - onlu one type of functioning cone cell

43
Q

symptoms of rod monochromacy?

A

-complete colour blindness
-photophobia
-poor visual acuity

44
Q

what monochromacy type is worse?

A

rod monochromacy

45
Q

what type of congenital colour deficiencies cause colour vision defects?

A

-protanope
-deuteranope
-protanomalous trichromat
-deuteranomalous trichromat

46
Q

what type of congenital colour defiencies caise blue-yellow defects?

A

-tritanope
-tritanomalous trichromat

47
Q

what cause acquired colour vision defects?

A

disease processes, stroke, injury, trauma, toxicity which cause damage to any part of the visual pathway responsible for the processing of colour

48
Q

how are acquired colour defects classified?

A

using Kollner’s classification, it classifies the type of acquired colour vision defects putting them into three broad groups trying to match them from the known groups in congenital colour defects

49
Q

what are the 3 types of colour deficiencies in Kollner classification system?

A

-type 1: red-green
-type 2: red-green
-type 3: blue-yellow

50
Q

What is type 1 acquired deficiency associated with?

A

-progressive cone dystrophies
-chloroquine toxicity

51
Q

What is type 3 acquired deficiency associated with?

A

-Cataract
-Glaucoma
-AMD
-Diabetic retinopathy

51
Q

What is type 2 acquired deficiency associated with?

A

-Optic neuropathy
-Ethambutol toxicity

52
Q

what are the most common acquired colour vision defects?

A

blue yellow (type3)

53
Q

why does cataract cause type 3 defect?

A

When the lens yellows with age, it causes absorption of shorter wavelengths of light

54
Q

how can acquired colour vision defects be used to diagnose disease?

A

-Diabetic retinopathy also is associated with type 3 defect which can occur before retinopathy actually occurs - can be used as a warning
-2009 study detected colour vision changes before visual defects in open angle glaucoma - typically expect type 3 but any CV changes can occur
-AMD is associated with type 3 defect in early stages of disease

55
Q

how can you use colour vision to test for optic neuritis?

A

typically causes red-green colour deficiency:
-Can test this in desaturated red test: Get a red target and tell the patient to occlude one eye and then switch between the eyes. Affected eye will see the red colour as more washed out/ dull which indicates optic neuritis

56
Q

what is cerebral achromatopsia?

A

an acquired colour vision defect due to damage of V4 where you can only see in black and white

57
Q

what is agnosias?

A

object recognition defect

58
Q

what us anomia?

A

inability to name colours properly

59
Q

when can drugs affect colour vision

A

if the dose is exceeded or treatment is prolonged

Optometry class OP2501 (14 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions