Vision
Module 18
• Human’s most
dominating sense
• If multiple senses are
competing, vision will
overwhelm the others
• baby
The height of a wave gives us its intensity
(brightness).
The length of the wave gives us its hue
(color).
The spectrum
of
electromagnetic
energy
Video
Differing Eyes
Bee detects reflected ultraviolet wavelengths
The Eye
• Cornea
– Outer transparent
coating that protects the
eye’s interior and
focuses incoming light
The Eye
• Pupil
– Adjustable opening in the
center of the eye
– Lets light in
• Iris
– Ring of muscle that forms
the colored portion of the
eye around the pupil
– Controls the size of
opening allowing various
degrees of light in
Just FYI
• Blue eyes – less
pigment in Iris – more
susceptible to red eyes
• Iris does not have
enough time to close
and adjust…shines to
the back of the
eye…showing blood
vessels and tissue at the
back of the eye called
the retina
The Eye
• Lens
– Transparent structure
behind the pupil
– Changes shape through
accomodation to focus
images on the retina
– Cataracts are the
clouding of the eye’s lens
The Eye
• Accommodation
– Change in the curvature
of the lens that enables
the eye to focus on
objects at various
distances
Vision Impairments
• Myopia
– Nearsightedness
– Can’t see far away
objects as well
• Hyperopia
– Farsightedness
– Decreased vision for up
close objects
The Eye
• Retina
– Light-sensitive
membrane at the back
of the eye
– Contains millions of
receptors for vision
– Begins the processing of
visual information
The Eye
• Optic Nerve
– Nerve that carries neural
impulses to the brain
• Dissection Video
The Retina
• Light energy rods and
cones bipolar cells 
ganglion cells
• Bipolar cells
– Collect neural signals from
rods and cones
– Transfer messages to
ganglion cells
• Ganglion cells
– Organize the neural signals
– Axons converge into optic
nerve
Receptors in the Eye
• Rods
– Peripheral retina
– Detect black, white, and
gray
– Twilight or low light
• Cones
– Near center of retina –
mainly in the fovea
– Fine detail and color vision
– Daylight or well-lit
conditions
Receptors in the Human Eye
Cones
Rods
Number
6 million
120 million
Location in
retina
Center
Periphery
Sensitivity in
dim light
Low
High
Color sensitive?
Yes
No
Vision to the brain
ve then carries the neural signals to
ry visual cortex
sm (Ki-asm) crosses to opposite
re of the brain
nsferred to the thalamus where it is
the visual cortex in the occipital
Vision from the Eye to the Brain
Visual Information Processing
• Feature Detectors
– David Hubel and Torsten
Wiesel
– Located in the visual cortex
– nerve cells in the brain that
respond to specific
features
• Shape
• Angle
• Movement
• Sam I Am
Visual Information Processing
• Parallel Processing
– Processing of several aspects of an object
simultaneously
– Crash Course