Pseudoisochromatic plates Flashcards
What colour defect does Ishihara screen for?
R-G
On Ishihara, how many seconds should you show the px each page?
4 seconds
On Ishihara, which plates are transforming and what does this mean?
Plates 2-9
Numbers will appear different to an anomalous trichromat, and a dichromat will see no number
On Ishihara, which plates are vanishing and what does this mean?
Plates 10-17
Both anomalous trichromats and dichromats will see no number
On Ishihara, which plates are hidden digit and what does this mean?
Plates 18-21
CV deficiencies will see a number, ‘normals’ won’t see a number
On Ishihara, which plates are classification and what does this mean?
Plates 22-25
Determines the severity of the defect - depending on severity, px will see one or both numbers
On the classification plates of Ishihara, when the number on the right is more obvious, what does this mean?
Protan deficiency
On the classification plates of Ishihara, when the number on the left is more obvious, what does this mean?
Deutan deficiency
On Ishihara, which plates are pathways and what does this mean?
Plates 26-38
Images of pathways instead of numbers, for use with small children or non-verbal pxs
What is a disadvantage of the pathway plates on Ishihara?
Reduced efficiency due to needing longer presentation time
What is sensitivity?
The proportion of true positives picked up by a test - e.g. how many people who actually have a deficiency are picked up.
What is specificity?
The proportion of true negatives picked up by the test - e.g. how many people are not picked up on test who are not deficient.
When doing rapid screening on Ishihara, how many of each plate should you use?
Demonstration
4 transformation
2 vanishing
Classification (if relevant)
On Ishihara, should you show everyone the classification plates? Why?
No
If they pass the rest of the test with no errors, they are not CV deficient, so no classification is needed.
What are MacAdam ellipses?
On the CIE diagram, ovals of varying sizes and orientations within which all the colours look the same