Pseudoisochromatic plates

Question 1

What colour defect does Ishihara screen for?

Answer 1

R-G

Question 2

On Ishihara, how many seconds should you show the px each page?

Answer 2

4 seconds

Question 3

On Ishihara, which plates are transforming and what does this mean?

Answer 3

Plates 2-9
Numbers will appear different to an anomalous trichromat, and a dichromat will see no number

Question 4

On Ishihara, which plates are vanishing and what does this mean?

Answer 4

Plates 10-17
Both anomalous trichromats and dichromats will see no number

Question 5

On Ishihara, which plates are hidden digit and what does this mean?

Answer 5

Plates 18-21
CV deficiencies will see a number, ‘normals’ won’t see a number

Question 6

On Ishihara, which plates are classification and what does this mean?

Answer 6

Plates 22-25
Determines the severity of the defect - depending on severity, px will see one or both numbers

Question 7

On the classification plates of Ishihara, when the number on the right is more obvious, what does this mean?

Answer 7

Protan deficiency

Question 8

On the classification plates of Ishihara, when the number on the left is more obvious, what does this mean?

Answer 8

Deutan deficiency

Question 9

On Ishihara, which plates are pathways and what does this mean?

Answer 9

Plates 26-38
Images of pathways instead of numbers, for use with small children or non-verbal pxs

Question 10

What is a disadvantage of the pathway plates on Ishihara?

Answer 10

Reduced efficiency due to needing longer presentation time

Question 11

What is sensitivity?

Answer 11

The proportion of true positives picked up by a test - e.g. how many people who actually have a deficiency are picked up.

Question 12

What is specificity?

Answer 12

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.

Question 13

When doing rapid screening on Ishihara, how many of each plate should you use?

Answer 13

Demonstration
4 transformation
2 vanishing
Classification (if relevant)

Question 14

On Ishihara, should you show everyone the classification plates? Why?

Answer 14

No
If they pass the rest of the test with no errors, they are not CV deficient, so no classification is needed.

Question 15

What are MacAdam ellipses?

Answer 15

On the CIE diagram, ovals of varying sizes and orientations within which all the colours look the same

Question 16

How are the colours on Ishihara chosen?

Answer 16

Chosen along colour confusion line for the defect they are testing
Outside of MacAdam ellipses so ‘normals’ can tell the difference
Background greys are chosen from further along colour confusion lines
Numbers are chosen from more central location on colour confusion line

Question 17

What deficiencies does the HRR test for? Does it assess severity?

Answer 17

R-G and tritan
Yes, assesses severity

Question 18

How many demonstration plates does the HRR test have?

Answer 18

4

Question 19

How many screening plates does the HRR test have?
How many plates screen for R-G defects and how many for B-Y?

Answer 19

6
4 R-G
2 B-Y

Question 20

How many diagnostic (assessing severity) plates does the HRR test have?
How many plates are for R-G defects and how many for B-Y?

Answer 20

14
10 R-G
4 B-Y

Question 21

Should you continue the HRR test if the px passes the screening plates?

Answer 21

No

Question 22

The HRR test has a reduced specificity, what does this mean?

Answer 22

It will pick up ‘defects’ on px’s who do not truly have a defect (false positive), so is not as reliable