W8 Colour Vision 1

what is the pigment present in cone photoreceptors

opsin

what is the function of red-green channel

compares L and M cone signals

what is the function of yellow blue channel

compares S cone signals with combined L and M signals

what causes a shift in peak sensitivity that results in differences in colour vision

genetic mutations

what is a congenital deficiency

present at birth, stable, bilaterally similar, affects entire VF

what is an acquired deficiency

progression/regression, affects one eye or both, only affcets one portion of the VF

what is the difference between wavelengths for normal colour vision

28nm

what is the difference between wavelengths for deutranomaly

3-11nm

what is the difference between wavelengths for protonomaly

3-6nm

anomalous trichromacy:

which cones are present for a deutranomalous

S

M'

M

NO L CONE

anomalous trichromacy:

which cones are present for a protonomalous

S

L'

L

No M CONE

Dichromacy:

which cones are present for a deutranope

S

L

Dichromacy:

which cones are present for a protanope

S

M

characteristics of acquired anomalies

associated with other visual defects (low VA)

onset after birth

type and severity changes with time

monocular testing required

equal prevalence in M and F

name some colour vision tests

ishihra

lanterns

hue discrimination

colour matching

what are the different functions of colour vision tests

What method of colour vision assessment does the CAD test use that makes it unique to other colour vision tests?

uses dynamic luminance contrast noise to isolate red-green and yellow-blue signals, allowing accurate measurement of chromatic sensitivity.

aging and colour vision loss

Chromatic sensitivity declines with age, with yellow-blue thresholds increasing more per year compared to red-green thresholds.

How does age-related macular degeneration (AMD) affect colour vision?

Patients with acquired colour vision loss due to AMD often experience a greater loss in yellow-blue sensitivity than red-green sensitivity.

How does diabetes affect chromatic sensitivity?

Patients with diabetes show significant loss in both red-green and yellow-blue colour vision, unrelated to age, disease duration, or control.

what are the different functions of colour vision tests

screening helps identify who has it

helps to classify the type of defect

quantify / grade severity of colour vision loss

diagnose dichromacy/ anomalous trichromacy