lecture2- colour vision anomolies

Question 1

what are the ways you can have abnormalities in colour vision?

Answer 1

-congenital
-acquired

Question 2

what does congenital mean?

Answer 2

present from birth

Question 3

what does acquired mean?

Answer 3

those with normal colour vision develop partial or total loss of vision

Question 4

what are the 3 types of congenital abnormalities?

Answer 4

• anomalous trichromacy
• dichromatic colour deficiency
• rod or cone monochromacy

Question 5

what is anomalous trichromacy?

Answer 5

occurs when all three cone types are present but one has an abnormal absorption curve. the severity of the anomaly depends on how abnormal is the absorption: thus there are simple anomalous observers and extreme anomalous observers

Question 6

what is dichromatic colour deficiency?

Answer 6

is caused by the absence of either L,M or S cones leading to protanopia, deuteranopia and tritanopia

Question 7

what is rod or cone monochromacy?

Answer 7

where there is only one photoreceptor type is present, so there is no colour perception

Question 8

what are the two types of acquired abnormalities of colour vision?

Answer 8

• cerebral achromatopsia/ dichromatopsia
• aging and diseases of the eye

Question 9

what is cerebral achromatopsia/ dichromatopsia?

Answer 9

is a selective loss/deterioration of colour vision associated with damage to temporal and occipital areas of the ventral pathway

Question 10

expand on aging and diseases of the eye

Answer 10

illness, ageing or trauma can cause CV anomalies and defects. typically disorders of the retinal vascular system and ageing result in yellow-blue losses cf. congenital anomalies and defects affect the red-green system. however optic nerve lesions, cone degeneration and poisons can cause red-green losses

Question 11

what are the 3 tests of colour vision?

Answer 11

-pseudoisochromatic plates eg ishihara plates
- anomaloscope
- farnsworth-munsell 100 hue test