PC - Clinical Assessment of Colour Vision - Week 9 Flashcards
Name 6 indications for testing colour vision.
- 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
Describe examples of why colour vision is important.
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
What is the prevalence of CVD in women vs men?
8% in women, 0.5% in women
Define protanopia/protanomaly.
Missing (-ope) or anomalous (-nomal) red cone photopigment
Define deuteranopia/deuteranomaly.
Missing (-ope) or anomalous (-nomal) green cone photopigment
Define tritanopia/tritanomaly.
Missing (-ope) or anomalous (-nomal) blue cone photopigment
What are the three components of testing for CVD?
Detection
Assessing severity
Congenital vs acquired
what do most tests for CVD rely on?
Colour confusions
Describe colour confusion for protan, deutan, and tritan using a chromaticity chart. Define the orientation for each.
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.
What are pseudoisochromatic plates, and how do they work? Why does it use its specific patterning?
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.
What is the most commonly used edition of pseudoisochromatic plates?
Ishihara’s Test
Describe the introduction plates of the ishihara test.
What 4 things are these plates used for?
- Checks VA is sufficient (6/18)
- Seen by all observers (normal and those with CVD)
- Demonstrates the test
- Detects malingerers
Describe the transformation plates of the ishihara test.
Combines hidden and vanishing parts.
Normal trichromats see one number, CVD afflicted see another.
Describe the vanishing plates of the ishihara test.
Trichromats see a number
CVD afflicted see nothing
Describe the hidden plates of the ishihara test.
Trichromats see random lines
CVD afflicted see a number
Describe the classification plates of the ishihara test, and what its used for.
2 plates with 2 numbers.
Each number uses a different confusion line to identify the defective cone system.
Consider the classification plate for the ishihara test. What would protans and deutans confuse?
Protans confuse red and grey
Deutans confuse purple and grey
Describe the tracing plates of the ishihara test. Which population is it suitable for?
A squiggly line of random direction is seen by trichromats.
Patient is asked to trace it out with a cottonbud.
Suitable for children.
Name 5 advantages of the ishihara test.
- High sensitivity and specificity
- Robust (not sensitive to illumination changes)
- Inexpensive
- Readily available
- Easy to administer
Which of the three protan, deutan, and tritan, can the ishihara test not account for?
Tritan (no tritan plates)
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.
No, 15 or fewer errors indicates a mild defect.
More than 15 is not an indication of higher severity.
What are the limitations of the ishihara test in terms of diagnosis?
Diagnosis by type is not very good, sometimes its wrong.
Describe the Richmond HHR, and the populatin its suitable for.
Uses pseudoisochromatic plates with shapes on them. Suitable for children.
Can the Richmond HHR detect protan, deutan, and tritan?
Yes, even tritan
What is the Richmond HHR typically used for?
Confirmation of ishihara testing
What does the Richmond HHR require patients to do?
Immediately identify the number of coloured symbols, where they are, and what they are.
Can the Richmond HHR provide detail of defect severity?
Yes
Describe the City University test, and the response time.
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.
Does the number of mistakes in the City University test indicate severity?
Yes
Describe the Farnsworth F2 test, and the defect it detects.
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.
Describe the Lanthony album test, and the defect it detects. What is a problem with this test?
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.
Describe the Farnsworth D15 test.
Describe the test result, and compare normal and CVD results.
A series of 15 coloured, loose caps are placed in order of hue by the patient.
Describe the Lanthony desaturated D15 test.
Like Farnsworth D15, but is desaturated and harder to complete correctly.
Is it possible for someone with CVD to pass the Lanthony desaturated D15? Explain.
Yes, it means they have a very mild deficiency.
What is a disadvantage of Lanthony desaturated D15?
Poor specificity, normal trichromats make errors.
Describe the H16 test. What constitutes a fail?
Like Farnsworth D15, but more saturated. More than 3 errors is a fail.
Describe the Farnsworth Munsell M 100 hue test.
What is it used for?
Has 85 closely spaced colours that must be arranged.
Used for colour aptitude assessment of in trichromats.
Describe Medmont C-100, and what its used for.
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.
How do anomaloscopes work? Name 2 disadvantages.
Instrument for colour matching.
Large and expensive.
Describe the process of diagnosing CVD.
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.
