Acquired Colour Vision 2

Question 1

What are some examples of conditions that may cause aquired colour vision deficiencies?

Answer 1

Media Opacites (red bias)

Retinal disorders such as cone dystrophies, retintitis pigmentosa

AMD

Diabetes

Choroid Oedema

Optic nerve disorders e.g. glaucoma, heriditary optic neuropathy , optic neuritis

Drug toxicitiy - numerous drugs have been identified to cause colour anomalies

Question 2

What are standard normal units for a CAD colour Vision test?

Answer 2

1 RG threshold unit

1 YB threshold unit

Question 3

How do you interpret a CAD Colour Vision Test?

Answer 3

Question 4

What does it mean if a px’s CAD colour vision results hit the grey dotted line?

[Like in the image below]

Answer 4

This means the px fails to see even the most saturated stimulus that can be presented on the display.

[The dotted lines are the phopho limits?]

Question 5

How can we diffrentiate between a congenital and acquired deficiency on a CAD colour vision test?

Answer 5

Increasing the size of the stimuli in the CAD test, the thresholds reduce for a px with an acquired deficiency but not for a congenital deficiency.

Question 6

What CAD results are typical of diabetic subjects?

Answer 6

• Diabetic subjects exhibit greater YB loss compared to RG
• High‐risk group reveal approximate equal YB and RG up to ~2 CAD units when the loss of YB becomes greater compared to RG loss.

Question 7

Why may we decide to use colour vision testing as a screening test?

Answer 7

Chromatic sensitivity is affected most and earliest in a number of diseases of the retina and optic nerve

Colour vision testing provides a means of early detection/diagnosis and is a potential biomarker for a number of diseases (and also could be used to follow‐up progressive changes with disease)

• Normal colour vision is a good indicator of normal functioning of the retina

Question 8

What adjustment must we remember to use/apply when interpreting results of elderly patients?

Answer 8

The age‐corrected CAD threshold limits provide a more accurate way of detecting monocular changes in colour vision caused by either retinal diseases or systemic conditions that affect the eye

Question 9

How do CAD thresholds look in a px with congenital colour vision deficiency?

Answer 9

They are symetrical between the right and left eye.

(Asymetrical thresholds are present in pxs with acquired colour vision deficiencies)