colour vision

Define dichromacy

Absent cone type or photopigment resulting in confusion of colours

what are the types of dichromacy

1. protanopia

2. deuteranopia

3. tritanopia

which cones are absent in protanopia

L cones ( red sensing)

which cones are absent in deuteranopia

M cones ( green sensing)

which cones are absent in tritanopia

S cones (blue sensing)

protanopes have a ____________ sensitivity to long wavelengths of light

reduced

which type of dichromacy results in normal spectral sensitivity

Deuteranopia

which type of dichromacy is the most rare

tritanopia

what is small field tritanopia

everyone with normal colour vision will struggle to see blue light when the target is 20 mins of arc or less due to the absence of S cones

what are the two types of colour deficiencies

congenital and acquired

what are congenital colour vision deficiencies

present from birth and a result of inherited abnormality

which gender is more likely to have colour vision deficiencies

males

what % of males have colour vision deficiencies

8%

what % of females have colour vision deficiencies

0.5%

what is acquired colour vision deficiencies

deficiencies in colour vision caused by ocular disease

what are the types of trichromacy

1. protanomaly

2. deuteranomaly

3. tritanomaly

which individuals are true colour blind

monochromats

which photoreceptor is missing in monochromats

cones

which type of light conditions do monochromats prefer

dim light levels

which eye condition is likely to be present in monochromats

nystagmus

what is protanomaly

l pigment ( red sensitive ) is replaced with M like hybrid pigment making the individual less sensitive to long wavelengths and shades of red

what is deuteranomaly

M pigment ( green sensitive) is replaced by l like hybrid pigment making the individual less sensitive to green pigments

which type of colour deficiency is the most common

deuteranomaly

1 in how many boys have colour vision deficiencies

12

what are the three types of cones

1. s ( blue sensitive)

2. m ( green sensitive )

3. L ( red sensitive)

what is the principle of univariance

The input of a cone may vary in wavelength and radiance, but the output varies only in
one dimension (the degree of hyperpolarization of the cell) and reflects the total quantum catch

what are the peak sensitivity for cones

420, 530, 560

what are the three physical and measurable descriptions of light colours

1. hue

2. saturation

3. brightness

what is the munsell system

colour ordering system whereby colours may be specified by three variables

what are the variables for the munsell system

1. hue

2. value

3. chroma

complementary colours

pairs of colours whose mixtures produce achromatic grey or white

Define Metameric Colours (Metamers)

colours that match perceptually, but that have different spectral composition

what is the most common test for colour vision deficiencies

Ishihara test

can the tests distinguish between opia and anomaly

no

what colour deficiency is tested using the Ishihara test

red gree CVD

how does the Ishihara test work

by exploiting the confusion lines of CVD

what is the first plate in the Ishihara

visible to everyone

what types of plates are there in the Ishihara test book

1. transformation

2. vanishing

3. hidden

how many errors are considered failure in an Ishihara test

4 or more

under what conditions should the Ishihara test be perfoemed

daylight conditions

what does the HRR test stand for

hardy rand rittler test

what is the colour arrangement tests called

D15

which test is definitive to test for red green CVD

anomaloscope

which test is electronically generated

FM100

which questionnaire is administered to patients with and without congential CVD

Steward and cole

Each cap in the fansworth D15 test was selected to have

the same munsell value

what is the trichromactic young helmholtz theory

the cones are sensitive to three different colors: green, blue, and red. When these colors are combined, eyes can tell a difference between millions of colors

what is the opponenet hering colour theory

what is stage colour theory