Clinic Prep: Colour Vision Revision Flashcards
List 5 indications for a colour vision assessment
When advice is required to tailor the learning needs of kids
When advice is required for day-to-day visual tasks
When vocational advice is required (e.g. can I be a pilot)
When a certificate of visual fitness has been requested (e.g. for an occupation or licence)
When an ocular disease is suspected that can affect colour vision (Some conditions will have deficiencies like B-Y or R-G. So do an ishihara etc.)
What colour vision defect may AION/GCA result in? (2)
Achromatopsia [partial or total absence of CV]
Dyschromatopisa [deficiency in perception of colours]
What colour vision defect may NAION (Non-arteritic ischaemic optic neuropathy) result in?
R-G deficiency and red desaturation
What colour vision defect may a toxic/nutritional or an ischaemic optic neuropathy result in?
Dyschromatopsia. This can often be the first sign of this condition
What colour vision defect may a patient with any optic neuritis result in?
Dyschromatopsia and red desaturation. They can also have contrast/brightness problems (i.e. things appear less bright/sharp)
What colour vision defect may Leber’s syndrome involve?
Early B-Y then later R-G defect
What colour vision defect may Kjer’s disease involve?
B-Y defect
What type of colour vision deficiency can optic nerve diseases traditionally cause?
R-G deficiency
What colour vision deficiency (if present) is glaucoma primarily associated with?
B-Y deficiency
List the 3 broad categories of CVD
Protans (red cone problem)
Deutans (green cone problem)
Tritan (blue cone problem)
What is the most common type of CVD?
Deutanomaly (5% in males)
What percentage of men have a congenital CVD of some kind?
8%
What are the 3 steps in testing for CVD?
Detect (screening tests)
Assess severity (grading tests)
Determine if congenital vs acquired
List 4 types of screening tests for CVD. By what principle do these tests work?
Pseudochromatic (PIC) Plates
Hue discrimination (arrangement) tests
Lanterns
Anamolascopes
These tests rely on colour confusions across “confusion lines” on the CIE diagram
Provide an example of a CVD test that doesn’t rely on confusion lines
Medmont C-100
Describe what the 24 plates on Ishihara represent, using a mnemonic to guide you
“I Think Vinay Has Carpal Tunnel”
Introduction (plate 1)
Transformation (plates 2-7)
Vanishing (8-13)
Hidden (14-15)
Classification (16-17)
Tracing (18-24)
What are 2 purposes of the introduction plate?
Checks VA is sufficient (6/18)
Detects malingerers
How do transformation plates work?
Normal trichromats see one figure, CVD sees a different figure/number
How do vanishing plates work?
CVD sees nothing
How do hidden plates work?
CVD sees a figure whereas normals dont’
How do classification plates work?
Use different confusion loci to identify which cone system is defective.
Protans confuse red/grey (say “6”), Duetans confuse purple and grey (say “2”)
If both numbers seen –> milder defect/less indication of CVD
If no numbers seen –> severe RG with high density macula pigment
When are tracing plates used?
Suitable for children or patients who can’t read numbers
List 5 benefits of ishihara
High sensitivity and specificity
Robust
Inexpensive
Readily available
Easy to administer
List 3 limitations of ishihara
No tritan plates
Number of errors not really an index of severity
Diagnosis by type not very good, sometimes can be wrong
