PC - Clinical Assessment of Colour Vision - Week 9

Question 1

Name 6 indications for testing colour vision.

Answer 1

• First visit of the patient
• When advice is needed for the learning needs of children
• When advice is needed for day to day activities
• When vocational advice is needed
• When a certificate of visual fitness is needed
• When an ocular disease is suspected

Question 2

Describe examples of why colour vision is important.

Answer 2

As an optometrist, its needed to look for signs of disease
Electrician, for wires
Pilot
Whether food is cooked
Identifying fruit/vegetables
Identifying danger
Identifying trauma to self, like blood

Question 3

What is the prevalence of CVD in women vs men?

Answer 3

8% in women, 0.5% in women

Question 4

Define protanopia/protanomaly.

Answer 4

Missing (-ope) or anomalous (-nomal) red cone photopigment

Question 5

Define deuteranopia/deuteranomaly.

Answer 5

Missing (-ope) or anomalous (-nomal) green cone photopigment

Question 6

Define tritanopia/tritanomaly.

Answer 6

Missing (-ope) or anomalous (-nomal) blue cone photopigment

Question 7

What are the three components of testing for CVD?

Answer 7

Detection
Assessing severity
Congenital vs acquired

Question 8

what do most tests for CVD rely on?

Answer 8

Colour confusions

Question 9

Describe colour confusion for protan, deutan, and tritan using a chromaticity chart. Define the orientation for each.

Answer 9

Protan - lines fan outward from the top right corner
Deutan - horizontal, slightly oblique (top left to bottom right)
Protan - fan outward from the bottom corner
Each line represents a colour confusion, where any two colours selected along a single line would be seen as the same colour by the individual with the given conditions.

Question 10

What are pseudoisochromatic plates, and how do they work? Why does it use its specific patterning?

Answer 10

They are spots of colour that are coloured such that they fall on the same line of confusion.
Individuals with CVD will not be able to see the numbers.
circles are used so that the distinct outline of the number is hidden.

Question 11

What is the most commonly used edition of pseudoisochromatic plates?

Answer 11

Ishihara’s Test

Question 12

Describe the introduction plates of the ishihara test.

What 4 things are these plates used for?

Answer 12

• Checks VA is sufficient (6/18)
• Seen by all observers (normal and those with CVD)
• Demonstrates the test
• Detects malingerers

Question 13

Describe the transformation plates of the ishihara test.

Answer 13

Combines hidden and vanishing parts.

Normal trichromats see one number, CVD afflicted see another.

Question 14

Describe the vanishing plates of the ishihara test.

Answer 14

Trichromats see a number

CVD afflicted see nothing

Question 15

Describe the hidden plates of the ishihara test.

Answer 15

Trichromats see random lines

CVD afflicted see a number

Question 16

Describe the classification plates of the ishihara test, and what its used for.

Answer 16

2 plates with 2 numbers.

Each number uses a different confusion line to identify the defective cone system.

Question 17

Consider the classification plate for the ishihara test. What would protans and deutans confuse?

Answer 17

Protans confuse red and grey

Deutans confuse purple and grey

Question 18

Describe the tracing plates of the ishihara test. Which population is it suitable for?

Answer 18

A squiggly line of random direction is seen by trichromats.
Patient is asked to trace it out with a cottonbud.
Suitable for children.

Question 19

Name 5 advantages of the ishihara test.

Answer 19

• High sensitivity and specificity
• Robust (not sensitive to illumination changes)
• Inexpensive
• Readily available
• Easy to administer

Question 20

Which of the three protan, deutan, and tritan, can the ishihara test not account for?

Answer 20

Tritan (no tritan plates)

Question 21

Consider the number of errors an given individual has on an ishihara test. Can it be used as an indication of severity?
Explain in terms of the number of errors.

Answer 21

No, 15 or fewer errors indicates a mild defect.

More than 15 is not an indication of higher severity.

Question 22

What are the limitations of the ishihara test in terms of diagnosis?

Answer 22

Diagnosis by type is not very good, sometimes its wrong.

Question 23

Describe the Richmond HHR, and the populatin its suitable for.

Answer 23

Uses pseudoisochromatic plates with shapes on them. Suitable for children.

Question 24

Can the Richmond HHR detect protan, deutan, and tritan?

Answer 24

Yes, even tritan

Question 25

What is the Richmond HHR typically used for?

Answer 25

Confirmation of ishihara testing

Question 26

What does the Richmond HHR require patients to do?

Answer 26

Immediately identify the number of coloured symbols, where they are, and what they are.

Question 27

Can the Richmond HHR provide detail of defect severity?

Answer 27

Yes

Question 28

Describe the City University test, and the response time.

Answer 28

A test circle of a specific colour is surrounded by 4 other comparison coloured circles.
Patient is to identify the most identical one to the central circle within 3 seconds.

Question 29

Does the number of mistakes in the City University test indicate severity?

Answer 29

Yes

Question 30

Describe the Farnsworth F2 test, and the defect it detects.

Answer 30

A background of purple circles.
Within are outlines of 2 squares, made of circles.
One is green, the other is blue.
Trichromats see both squares, green is clearer.
CVD afflicted see only blue, or blue is clearer.

Question 31

Describe the Lanthony album test, and the defect it detects. What is a problem with this test?

Answer 31

Has a big square made of circles, with a smaller square made of circles at one of its corners.
Patient must report the location of the smaller square.
Assesses and grades tritan defects.
Slight and moderate CVD may still pass.

Question 32

Describe the Farnsworth D15 test.

Describe the test result, and compare normal and CVD results.

Answer 32

A series of 15 coloured, loose caps are placed in order of hue by the patient.

Question 33

Describe the Lanthony desaturated D15 test.

Answer 33

Like Farnsworth D15, but is desaturated and harder to complete correctly.

Question 34

Is it possible for someone with CVD to pass the Lanthony desaturated D15? Explain.

Answer 34

Yes, it means they have a very mild deficiency.

Question 35

What is a disadvantage of Lanthony desaturated D15?

Answer 35

Poor specificity, normal trichromats make errors.

Question 36

Describe the H16 test. What constitutes a fail?

Answer 36

Like Farnsworth D15, but more saturated. More than 3 errors is a fail.

Question 37

Describe the Farnsworth Munsell M 100 hue test.

What is it used for?

Answer 37

Has 85 closely spaced colours that must be arranged.

Used for colour aptitude assessment of in trichromats.

Question 38

Describe Medmont C-100, and what its used for.

Answer 38

A yellow flicker is presented on a handheld device with green and red LEDs. With an adjustable knob the flicker is made minimal or disappear entirely.
Scale is red for protan and green for deutan.

Question 39

How do anomaloscopes work? Name 2 disadvantages.

Answer 39

Instrument for colour matching.

Large and expensive.

Question 40

Describe the process of diagnosing CVD.

Answer 40

Begin with detection using: Ishihara, Richmond HHR, City University, Farnsworth F2, and Lanthony album - a pass means normal or very mild CVD.

If they fail the above - Farnsworth D15 - if they pass, then Lanthony desaturated D15 - if they pass, then very mild defect.
-If they fail Lanthony desaturated D15, then mild CVD.

If they fail Farnsworth D15, then moderate-severe CVD, do H16 test - pass is moderate CVD.
Fail is severe CVD.
Use Medmont C-100 to determine protan or deutan.