Color Vision and Associated
Disease
Learning objectives
• Understand the physiology of color vision and
its role in visual perception.
• Identify common color vision defects and their
impact on daily activities.
• Learn the diagnostic techniques for assessing
color vision.
Physiology of color vision
• Color vision is the ability of the visual system
to distinguish objects based on the
wavelengths of light they reflect. This function
is mediated by specialized cells in the retina
and complex neural pathways that interpret
color information.
Visible light
Structure Involved in Color Vision
• Retina: Contains photoreceptors (cones and
rods) that detect light.
• Photoreceptors:
• Cones: Responsible for color vision; sensitive to
different wavelengths.
• Rods: Provide vision in low light but are not
involved in color perception.
Structure Involved in Color Vision
Structure Involved in Color Vision
• Fovea: Central part of the retina, rich in cone
cells, provides sharp central vision.
• Optic Nerve & Visual Pathway: Carries signals
to the brain for color interpretation.
Types of Cone Photoreceptors
• Each type of cone contains a unique
photopigment that makes it sensitive to a
particular range of wavelengths:
• S-Cones (Short-wavelength sensitive): Peak
sensitivity around 430 nm (blue light).
• M-Cones (Medium-wavelength sensitive):
Peak sensitivity around 530 nm (green light).
• L-Cones (Long-wavelength sensitive): Peak
sensitivity around 560 nm (red light).
Types of Cone Photoreceptors
Types of Cone Photoreceptors
• The combination of inputs from these three
cone types enables trichromatic vision, which
allows the brain to perceive a wide range of
colors.
Mechanism of Color Perception
• Phototransduction: Light is absorbed by the
cone photopigments. The photopigments
undergo a chemical change, initiating an
electrical signal.
Mechanism of Color Perception
• Signal Transmission:
• Signals from cones are transmitted via bipolar
cells to ganglion cells.
• The opponent color theory plays a role:
• Red vs. Green
• Blue vs. Yellow
• Black vs. White (luminance pathway)
Mechanism of Color Perception
• Neural Processing: Signals travel through the
optic nerve to the lateral geniculate nucleus
(LGN) of the thalamus and then to the visual
cortex in the occipital lobe.
• The brain compares input from the different
cone types to create the sensation of color.
Theories of color vision
• Trichromatic Theory:
• Proposed by Young and Helmholtz. Color
perception is based on the activity of three
types of cones (S, M, L).
Theories of color vision
• Opponent-Process Theory:
Proposed by Ewald Hering.Color perception is
based on opposing pairs: Red-Green, Blue-
Yellow, and Black-White.
Both theories are valid: the trichromatic theory
explains the photoreceptor level, while the
opponent-process theory explains neural
processing at later stages.
Types of color vision deficiencies
• Red-green color vision deficiency
• Blue-yellow color vision deficiency
• Complete color vision deficiency
Red-green color vision deficiency
Deuteranomaly is the most common type of red-green
color vision deficiency. It makes certain shades of green
look more red. This type is mild and doesn’t usually get
in the way of normal activities.
Protanomaly makes certain shades of red look more
green and less bright. This type is mild and usually
doesn’t get in the way of normal activities.
Protanopia and deuteranopia both make someone
unable to tell the difference between red and green at
all.
Red-green color vision deficiency
Blue-yellow color vision deficiency
• There are 2 types of blue-yellow color vision
deficiency:
• Tritanomaly makes it hard to tell the difference
between blue and green and between yellow and
red.
• Tritanopia makes someone unable to tell the
difference between blue and green, purple and red,
and yellow and pink. It also makes colors look less
bright.
Blue-yellow color vision deficiency
Complete color vision deficiency
• If a person have complete color vision
deficiency, you can’t see colors at all. This is
also called monochromacy or achromatopsia,
and it’s rare. Depending on the type, you may
also have trouble seeing clearly, and you may
be more sensitive to light.
Complete color vision deficiency
Achromatopsia
Impact on daily life
• Difficulty in color recognition
• Use of technology
• Safety issues
• Career limitations
• Educational challenges
• Social and psychological effect
Diseases that effects color vision
• Glaucoma
• Macular degeneration
• Parkinson’s disease
• Multiple sclerosis
• Alzheimer’s Disease
Note for color vision testing
- Use proper illumination (day light)
- Explain test for the patient.
- In screening for congenital diseased test is
done binocularly and monocularly for
acquired abnormality.
- Patient should use his or her near correction.
- Avoid tinted spectacles or contact lenses
CV Assessment
• Color Vision Tests
o Pseudoisochromatic Test Plates
• Ishihara Plates,
o Arrangement Tests
• The Farnsworth D-15 test
o Matching and Pointing
o BRVT Basic color identification Test
ISHIHARA TEST
D-15 Color Test
Lanthony D15 test
