Color Vision Testing

Name some color vision tests.

simple: red-cap test

more complex: pseudoisochromatic plates

What is the red-cap test?

a screener in clinical instances where optic neuritis is a differential diagnosis based on signs/symptoms

• use the red cap of a tropicamide/phenylepherine bottle

• presented to the normal eye first then abnormal eye and assigned an amount of difference

What do you ask the patient with the red-cap test?

“If the OD view is 100%, how would you rate the OS view?

What are the advantages of the red-cap test?

• readily available 

• easy to perform 

• easy to understand results 

What are the cons of the red-cap test?

• pt may subjectively see a difference even if none is present

• may not change your decision of which to test further

What are the pseudoisochromatic plates?

one of the most commonly administered color vision tests, consisting of a number of plates arranged into a booklet

falsely the same color depending on your color vision deficiency

What are the advantages of the pseudoisochromatic plates?

relatively inexpensive and commonly found in optometry clinics 

What are the disadvantages of the pseudoisochromatic plates?

they do not distinguish between dichromatic and anomalous trichromatic vision (-nopes vs ‘nomalous)

What is the red/green pass/fail test that cannot differentiate between protains/deutans?

ishihara (easy to understand- works by pass/fail criterion)

What is the HRR plate?

it’s superior to the ishihara, more difficult to understand, determines level of deficiency

• differentiate between protan/deutan

• determine severity 

• detect blue-yelow anomalies 

How does the pseudoisochromatic plate work?

figures and backgrounds fall on a common color confusion line which confused the patient with a color anomaly because it uses colors that appear to be isochromatic (equal color) but they are pseudoisochromatic 

In simpler terms, how does the pseudoisochromatic plate work?

to a pt with a color deficiency, the embedded figure is indistinguishable from the background

What are these lines called?

color confusion lines

What HRR plate is this?

• Plate 20, a purple circle and pink triangle 

• purple falls on the deutan confusion line (they will see the pink triangle)

• pink falls on the protan confusion line (they will see the purple circle) 

When the 1-10 screener portion is completed successfully on the HRR

the test is done and you do not have to proceed to the corresponding part of the test

How do you score for defects?

the most checks labels the type of defect (seems backwards) more checks, is worse

Review: The CFF increases in direct proportion to the log of the stimulus area

granit-harper law 

What indicated severity on the HRR test scoring?

the last error indicates severity 

What is the brightness setting for yellow?

17

What is the only color vision test administered binocularly?

Farnsworth Lantern

How many presentations are in the farnsworth lantern?

9 presentation 

Any error out of the 9,

repeat the test 2 more times in a random/different presentation

Lighting conditions for color vision tests, what do we use?

always use illuminant C because others can skew the results for better or worse

What does a colored filter do?

What are enchroma lenses?

lenses designed to help the anomalous trichromats see colors similar to a normal trichromat