wk7: ND - Anomolous Trichromacy Flashcards
What percentage of males have protanomoly?
1%
What percentage of males have Deutranomaly?
5%
How does the luminosity of red light compare between normal trichromats, protanomals, and deuteranomals?
Normal: is normal, value of 1
Deuteranomals: slightly lower
Protanomals: much lower
How does the luminosity of green light in deuteranomals compare to normal?
Slightly lower (is around 0.8 or so compared to 1 for normals)
How does the luminosity of green light in protanomals compare to normal?
Slightly higher
Is there much variation in the wavelength discrimination for protanomals and deuteranomals?
Yes. They both have much variation between subjects
Where is the neutral point for saturation discrimination in protanomals and deuteranamols?
They don’t have a neutral point for saturation discrimination. It’s a trick question haha!
Do protanomals and deuteranomals experience more or less saturation of spectral colours compared to normals?
Less, so spectral colours look more desaturated
Summarise the colour perception of anomalous trichromats compared to normals in 4 points
Anomalous trichromats see:
- Metamers differently
- Fewer colours (poorer wavelength discrimination, and deltaP)
- Saturated colours appear desaturated (poorer deltaP)
- PA have reduced luminosity to red (also DA very slightly)
What is the function of the Nagel Anomaloscope?
Provides definitive diagnosis of the congenital protan-deutan colour vision defects
How does the Nagel anomaloscope work?
It’s a colour matching instrument. One of the knobs controls intensity of the yellow (589nm) sodium field, and the other knob controls the ratio of lithium red (670nm) and mercury green (546nm). Task is to match hemifields
How do deuteranomals make matches with yellow?
by adding more green
How do protanomals make matches with yellow?
by adding more red
How can opsin genes be abnormal/compromised? (4)
Completely missing from gene array
Point mutations
Major sequence/deletions
Unequel crossing over (between M and L cones)
What do point mutations in opsin gene lead to?
dysfunctional photopigment. It’s very rare that you’d have a functional photopigment after a point mutation
What percentage homologous is the S pigment with M and L pigment?
43% homologous
How similar are M and L pigments?
96% mutually identical
When adding red/green to match with yellow, will deuteranopes have to change intensity of the yellow?
No. Protanopes will though because the red is less luminous for them and makes the overall mixture dimmer
What are Hybrid genes?
Genes created from a mismatch of parent genes from meiosis due to (in this example) multiple copies of the M gene, which make a misalignment more likely
How are anomalous trichromats similar but different from normal trichromats?
While they need 3 primaries to match another colour in a colour matching experiment, the matches they make are different from normals. They often reject colour matches made by normals
