Acquired Colour Vision Defects Flashcards
What can cause acquired CV defects?
Medication
Injury/Trauma
Disease
What are Kollner’s classifications of acquired CV defects?
Blue-yellow blindness
Progressive red-green blindness
What are some features of acquired CV defects?
Can be monocular
VA and VFs can be affected
Severity varies dependant on cause
Prevalence equal between genders
Not easily classified
What occurs in blue-yellow blindness?
What type of disease does it tend to occur in?
Blue-yellow perception changes first, followed by red-green later
Retinal disease
What occurs in red-green blindness?
What type of disease does it tend to occur in?
Blue-yellow and red-green both affected, but red-green more noticeable
Optic nerve or cortex affected
What is Kollner’s type 1 classification and what are they associated with?
Red-green - similar to protans (reduced L wavelength sensitivity)
Progressive cone dystrophies
Chloroquine toxicity
What is Kollner’s type 2 classification and what are they associated with?
Red-green - similar to deutans (reduced M wavelength sensitivity)
Optic neuropathy
Ethambutol toxicity
What is Kollner’s type 3 classification and what are they associated with?
Blue-yellow - similar to tritans (reduced S wavelength sensitivity)
Cataract
Glaucoma
AMD
DR
What happens to CV when a cataract develops?
The yellowing of the lens causes a shift in the wavelengths transmitted to the retina (yellow lens absorbs blue wavelengths) so blue-yellow defect occurs - vision becomes more yellow
How can CV testing help clinically?
Helps to detect retinal disease early - before any other symptoms are noticed.
What type of defect is seen in AMD and why?
Type 3 (blue-yellow)
Blue cones more easily damaged
What type of defect is seen in DR?
Type 3 (blue-yellow)
What type of defect is seen in POAG and why?
Type 3 (blue-yellow)
Due to damage of ganglion cells/blue cones due to increased IOP
What type of defect is seen in Optic Neuritis and why?
Progressive red-green
Demyelination of optic nerve
What is achromatopsia?
No CV - black and white vision
What is anomia?
Inability to name colours appropriately
What is hemiachromatopsia?
Loss of colour in one half of vision (due to damage only on one side of vision)
When is the most common time that a medication will cause CV defects?
Prolonged treatment or dose exceeded
What are some examples of drugs which can cause red-green defects?
Ibuprofen
Chloroquine
Streptomycin
What is an example of a drug which can cause blue-yellow defects?
Chloroquine
What can chloroquine cause other than CV defects? Is the effect reversable?
Bull’s eye maculopathy
Not reversable
What are some examples of toxins which can cause red-green defects?
Carbon monoxide
Lead
Thalium
What is cyanopsia?
Vision is ‘tinged’ blue after cataract removal - brain had adapted and was ‘adding’ blue back in when cataract present. Recedes after 2-3 weeks.
What defect can Leber’s optic atrophy cause?
R-G with deutan bias
