3. Acquired defects Flashcards
- What is the prevalence of acquired defects in males and females?
- When are acquired defects onset?
- Are acquired defects easy to classify?
- Are both eyes affected equally in acquired defects?
- Is VA and visual fields affected in acquired defects?
- Equal in males and females.
- After birth.
- Not easy to classify.
- Monocular differences.
- VA and visual fields may be affected.
Describe the appearance of blue- yellow blindness and where is it found?
Appearance: blue- yellow appearance changes 1st then red- green preserved longer.
Found in retinal diseases.
Describe the appearance of progressive red- green blindness and where is it found?
Colour vision is totally disturbed. Blue- yellow is changed, but deterioration most in red-green.
Found in: optic nerve to the cortex.
Describe type 1,2,3 classes and colours they defect?
Type 1: Red- green (similar to protan)
Type 2: Red- green (similar to deutan)
Type 3: Blue- yellow (similar to tritan)
What class of defect is assosiated with cataract, glaucoma, AMD and Diabetic retinopathy?
Type 3 (Blue- yellow)
What is the most common class of acquired defect?
Blue- yellow
(Type 3)
Where does type 3 defect occur (position in the visual pathway)
Can occur anywhere in the visual pathway
What is the most common pathologies seen in practice?- in anterior eye?
Cataracts
Describe what happens to the lens and absorption of light with patients that have cataracts?
As we age, lens starts to turn yellow and absorb short wavelengths- reducing sensitivity to the blue spectrum.
What type of defect is cataract- in terms of class?
Type 3 (blue- yellow)
What is the clinical importance of testing colour vision?
Can help identify early onset of retinal diseases.
What ocular condition is the most prevalent cause of visual loss in elderly people in the UK?
AMD
Type 3 (blue- yellow)
What ocular condition is the most common cause of blindness in working age group in the UK?
Diabetic Retinopathy
What happens to patients before they have diabetic retinopathy?
Colour vision is lost 1st before retinopathy
What is the class/ type of defect for diabetic retinopathy?
Type 3 (blue-yellow)
What causes the damage in primary open- angle glaucoma?
Damage is due to increased pressure on the optic nerve i.e, ganglions are dying
What is the class/ type of defect for primary open- angle glaucoma?
Type 3 (blue- yellow)
In any condition which one is defected 1st: Colour vision or visual feilds?
Colour vision
Which cones are the most sensitive to raised pressure?
Blue cones
Are patients with suspected acquired CV defects tested monocularly or binocularly?
Monocularly
What colour blindness is seen with optic neuritis?
Progressive red- green blindness
What is optic neuritis?
What causes it ?
Inflammation of optic nerve head.
Caused by: demyelination of optic nerve.
What is the likely chance of colour vision defect seen in optic neuritis?
100% colour vision defect is seen
What is the most common sign in that patients with optic neuritis notice? - what sign is noticed by patients?
Pain with eye movements
If a patient is diagnosed with optic neuritis, how can this diagnoses be supported/ tested?
Test colour vision to help diagnosis
Colour vision defects generally the result of a vascular lesion caused by? (2)
- Trauma
- Brain Damage
Achromatopsia is caused by damage to what part of the brain?
V4
What is bilateral achromatopsia?
Complete loss of colour vision: black and white vision.
What is agnosias?
Object recognition defect.
What is anomia?
Unable to differentiate between colours
What is hemi(semi)achromatopsia?
Damage to one side of the brain that causes partial colour vision defect
How can medications cause toxicity that leads to colour vision defects?
If medication is prolonged or dose is exceeded.
Colour vision defects can be used to monitor medication therapy, why?
They can cause visual losses
What is cyanopsia?
When a patients cataract is removed, they have a blue tinge to their vision.
This lasts for 2-3 weeks after cataract is removed.
3 likely causes of acquired colour vision defect?
- Pathology
- Toxins/ medication
- Trauma
